Pediatric Imaging Flashcards

Question

Meconium aspiration syndrome

Answer 1

Peripartum aspiration of meconium is typically seen in full-term and post-term neonates. Meconium is a highly irritating mixture of desquamated cells, bile pigments, and pancreatic enzymes that can cause signifcant respiratory distress. Imaging is characterized by ropy, coarse interstitial opacities. The lungs lose compliance and become especially susceptible to barotrauma and pneumothoraces. Outcome is variable, with much worse prognosis in the presence of a pneumothorax.

Answer 2

Unlike the previously described entities, which present with immediate respiratory distress, neontal pneumonia takes hours to days to develop. The most common pathogens are group B streptococus, S. aureus, and E. coli, which are acquired at birth from the vaginal flora. In neonatal pneumonia, the infection is not confined to the lung and is thought to represent neonatal sepsis. Typical signs of adult pneumonia, such as fever or elevated white count, are not reliable in neonates. Therefore it can be difficult to distinguish between neonatal pnemonia and TTN. A history of prolonged rupture of membranes or known maternal infection may suggest neonatal pneumonia. Neonatal pneumonia may lead to post-infectious pneumatocele, especially if the organism is S. aureus.

Answer 3

Congenital diaphragmatic hernia (CDH) represents herniation of abdominal contents into the thorax, most commonly through a left posterior defect in the diaphragm (Bochdalek). The primary complication is pulmonary hypoplasia on the affected side. Right-sided lesions with liver herniations are rare and have a poor prognosis. The key imaging finding is a mass in the thorax displacing the mediastinum. At birth, the herniated bowel may be fluid-filled and appear solid. However, shortly after birth, air fills the bowel to create the typical appearance. CDH is associated with bowel malrotation (95%), neural tube defects, and congenital heart disease.

Answer 4

Bronchopulmonary foregut malformations describe a range of congenital abnormalities of the embryonic foregut, which represent an inverse spectrum of normal to abnormal vasculature with normal to abnormal pulmonary parenchyma. Congenital lobar emphsema (CLE), a lesion of abnormal lung development without an associated vascular anomaly. Bronchial atresia is typically diagnosed later in life, and has been postulated by some authors to represent previously undiagnosed congenital lobar emphysema. Bronchogenic cyst. Congenital pulmonary airway malformation (CPAM), previously called congenital cystic adenomatoid malformation. Scimitar syndrome, a form of partial anomalous pulmonary venous return. Pulmonary arteriovenous malformation (AVM), an anomalous connection between the pulmonary artery and pulmonary veins, is a purely vascular malformation without any abnormal lung development.

Answer 5

Congenital lobar emphysema (CLE) is a syndrome of lobar air trapping. CLE has no affiliation with pulmonary interstitial emphysema (PIE), despite similar names. The most common cause of CLE is bronchomalacia, which results in airway collapse on expiration, leading to hyperinflation. CT can be preformed to evaluate for a cause of bronchial obstruction, which is only found in about half of the cases of CLE. CLE usually involves the upper and middle lobes. In the perinatal period, CLE is initially fluid-filled, but becomes radiolucent as the fluid clears. Eventually, lobar hyperexpansion can exert mass effect on surrounding structures. The involved lobe may herniate across the midline. It is essential not to mistake CLE for a tension pneumothorax, as a chest tube will increase respiratory distress.

Answer 6

Bronchial atresia is interruption of a bronchial branch with associated distal mucus impaction and hyperinflation. The left upper lobe is the most commonly affected. Bronchial atresia is usually incidentally diagnosed in adults and may be etiologically related to CLE. The bronchi distal to the the atretric segment become filled with mucus that cannot be cleared, ultimately forming a tubular mucocele. The distal airways are ventilated through collateral pathways and demonstrate air trapping, resulting in local hyperinflation. Imaging shows a geographic region fo hyperlucent lung with air trapping. A mucous plug may be visible just distal to the obstructed bronchial segment.

Answer 7

Congenital pulmonary airway malformation (CPAM) is a hamartomatous proliferation of terminal bronchioles that communicate with the bronchial tree. Congenital cystic adenomatoid malformation (CCAM) is an older term for the same entity. The arterial supply of CPAM arises from the pulmonary circulation. In contrast, sequestration derives its blood supply from the systemic circulation. The original classification (Stocker, revised in 2002) is important to be aware of, but the prognosis of CPAM depends more on the size of the lesion rather than its classification. Type I: One or more large cysts \>2 cm. Most common form. Type II: Multiple small cysts. Can be associated with renal agenesis. Type III: Innumerable tiny cysts too small to see, which appear solid. Type IV: Single large cyst, may be indistinguishable from a cystic pleuropulmonary blastoma, which is a rare malignancy that is the most common primary childhood lung tumor. CPAM may exert mass effect and is prone to infection. Surgery is usually recommended.

Answer 8

Sequestration is aberrant lung tissue with systemic blood supply, usually arising from the aorta. The key imaging finding is a systemic arterial vessel, which can be seen by Doppler ultrasound prenatally, or by CTA or MRA postnatally. The most common location is the left lower lobe. In contrast to CPAM, sequestration is usually solid. Two types of sequestration, intralobar and extralobar, are usually diagnosed by CT or MR Extralobar: External to the pleura, with primarily systemic venous drainage. May occasionally be below the diaphragm near the adrenal gland, where it may mimic an adrenal mass. Intralobar: Inside pleura, usually with pulmonary venous drainage.

Answer 9

Scimitar syndrome represents partial anomalous pulmonary venous return (PAPVR) from right lower lobe pulmonary veins into either the right atrium or IVC. In contrast to PAPVR, in total anomalous pulmonary venous retrun (TAPVR), all four pulmonary veins return blood to the right atrium, and an obligate right-to-left shunt is necessary for survival. The anomalous vein appears like a "scimitar" on the frontal radiograph, representing the scimitar sign. Scimitar syndrome can be associated with hypoplasia and hyperlucency of the right lung.

Answer 10

Bronchiolitis is an infection of the lower respiratory tract, most commonly caused by respirator syncytial virus (RSV). It is the leading cause of infant hospitalization in the US. Inflammation of bronchiolar epithelium leads to peribronchial infiltration by inflammatory cells. The resultant necrotic debris may lead to small airway obstruction, which is the hallmark of bronchiolitis. Clinically, bronchiolitis presents as increased work of breathing and wheezing in a child less than two years of age, usually with a viral upper respiratory prodrome. Bronchiolitis is primarily a clinical diagnosis. Radiographic findings include hyperexpanded lungs (best seen as flattening of the diaphragms) and increased peribroncial markings. These findings are subjective, with high variability among even experienced pediatric radiologists.

Answer 11

Bronchiolitis obliterans syndrome (BOS) is the final common pathway of small airway obstruction by inflammatory and fibrous tissue, which may be due to multiple etiologies. BOS may be post-transplant in origin, postinfectious (typically following viral or atypical bacterial pneumonia), or related to toxin or drug exposures. BOS is one of the most clinically important complications of pediatric allogeneic lung and bone marrow transplantation. Chest radiographs are usually normal or may show mild hyperinflation. CT demonstrates findings of small airway obstruction, including: Air trapping on expiratory views. Mosaic perfusion. Bronchiectasis and bronchial wall thickening. One complication seen in up to one third of young patients with post-infectious BOS is Swyer-James-MacLeod syndrome. Swyer-James-MacLeod syndrome is an acquired abnormality of pulmonary development secondary to BOS, which leads to a unilateral hyperlucent lung with volume loss. In particular, adenovirus infection is implicated in the etiology of Swyer-James-MacLeod. The key radiographic feature of Swyer-James-MacLeod is a unilateral, small, hyperlucent lung on the affected side. Note that Swyer-James-MacLeod is not a sequela of viral bronchiolitis (of which RSV is the most common cause), but is only seen after bronchiolitis obliterans, classically triggered by adenovirus infection.

Answer 12

Cryptogenic organizing pneumonia (COP) is a disorder of the distal airways characterized by filling of the bronchioles and alveoli with granulation tissue polyps. Bronchiolitis obliterans organizing pneumonia (BOOP) is an older term for the same entity and many authors recommend against using the term BOOP because of its confusion with bronchiolitis obliterans. BOOP is a completely different disease from bronchiolitis obliterans. The underlying histologic changes of COP are referred to as organizing pneumonia (OP). COP is the clinical syndrome of OP of unknown cause. OP may be secondary to infection, drug reaction, or inhalation. OP may also be a complication of stem cell transplant, but much less commonly than BOS. Radiographic features of COP/OP include multifocal migratory consolidations, ground glass opacities, and nodules. The atoll or reverse halo sign is thought to be relatively specific for OP and features a central lucency surrounded by ground glass.

Answer 13

Bronchiectasis is bronchial dilation, most commonly due to inflammation. Bronchiectasis can have a variety of causes in the pediatric population: Cystic fibrosis, Allergic bronchopulmonary aspergillosis, Post-infectious, Tracheobronchomegaly (Mounier-Kuhn), Aspiration, Intralobar sequestion, possibly due to recurrent infections. The signet-ring sign describes enlargement of the bronchiole, which appears larger than the adjacent pulmonary artery branch.

Answer 14

A unilateral hyperlucent lung is a common finding in pediatric chest radiology. The two most important acute diagnoses are endobronchial foregin body and pneumothorax.

Answer 15

Poland syndrome is an autosomal recessive syndrome of unilateral congenital absence (complete or partial) of the pectoralis major muscle. Associated anomalies of the ipsilateral arm and hand, including short metacarpals and syndactyly (joined fingers), may be present.

Answer 16

Anterior mediastinum - Normal thymus is sometimes mistaken as an anterior mediastinal mass. A special case is thymic rebound, which is physiologic regrowth of the thymus after chemotherapy, and should also not be mistaken for an anterior mediastinal mass. Lymphoma. Germ cell tumor. Thymoma (very rare in children). Middle mediastinum - Foregut duplication cyst. Neurenteric cysts, which are often associated with vertebral anomalies. Lymphadenopathy. Posterior mediastinum - Neuogenic tumors, including neuroblastoma, ganglioneuroblastoma, and ganglioneuroma.

Answer 17

The spinnaker sail sign is seen in pneumomediastinum and represents the thymus lifted off the mediastinum by the ectopic air. The spinnaker sail sign should not be confused with the sail sign, which is the rightward extension of the normal thymus.

Answer 18

The critical piece of the clinical history is whether the patient is cyanotic or acyanotic. After that's been established, the first imaging feature to evaluate is the pulmonary vascularity, which can be characterized as increased venous flow, increased arterial flow, or decreased arterial flow. Increased vascularity can be determined by examining the peripheral third of the lungs. Normally, there is very little blood flow peripherally; increased peripheral vasculature suggests either increased pulmonary arterial or pulmonary venous flow. 1) Increased pulmonary venous flow (pulmonary edema) is seen when the left ventricular outfow tract can't keep up with venous return. Can be caused by left heart insufficiency, an obstructive lesion of the left heart, or congestive heart failure. Peripheral 1/3 of the lungs shows indistinct vessels and septal markings. 2) Increased pulmonary artery flow, also called "shunt vascularity" tends to present in childhood rather than infancy. Increased arterial flow is caused by a left -\> right shunt, as the right side of the heart (which pumps blood to the lungs via the pumonary arteries) is pumping too much blood. The peripheral 1/3 of the lungs shows distinct, large-caliber vessels. 3) Decreased pulmonary arterial flow is due to right ventricular outflow tract insufficiency. Any lesion casuing decreased pulmonary arterial flow is ALWAYS cyanotic because not enough blood is being oxygenated in the lungs. Peripheral 1/3 of the lungs shows decreased vasculature. The second imaging feature is to evaluate the heart size. The heart can be normal in size, slightly enlarged, or massively enlarged. It is never smaller than normal (even in hypoplastic left heart syndrome). Additional findings, such as specific contour to the aorta and cardiac chambers, orientation of the aortic arch, and side of stomach bubble can help refine the diagnosis.

Answer 19

It is important to remember that an apparently enlarged heart and abnormal pulmonary vasculature can be due to other diseases in addition to congenital heart disease, including: Intracardiac tumor, such as rhabdomyoma, CHF due to a peripheral shunt (e.g., vein of Galen malformation or hepatic hemangioendothelioma), Mediastinal mass, Congenital diaphragmatic hernia with unaerated bowel.

Answer 20

Neonatal increased pulmonary venous flow (pulmonary edema) may be caused by: Hypoplastic left heart, similar in physiology to CHF (left ventricle cannot keep up with venous return). Aortic coarctation, which is a left ventricular outflow tract lesion. Congestive heart failure (CHF), which may be due to a primary cardiac anomaly or an extra-cardiac arteriovenous shunt, such as a veing of Galen malformation or hepatic hemangioendothelioma. Neonatal sepsis, typically seen in the setting of neonatal pneumonia. Increased pulmonary arterial flow (shunt vascularity) tends to present in childhood rather than the neonatal period. Increased pulmonary arterial flow can be caused by: Atrial septal defect (ASD). Ventricular septal defect (VSD). Patent ductus areteriosus (PDA). Endocardial cushion defect (ECD), also known as an AV canal defect, has a strong association with Down syndrome.

Answer 21

Decreased pulmonary vascularity with cardiomegaly: Ebstein anomaly. Decreased pulmonary vascularity without cardiomegaly: Tetralogy of Fallot. Usually increased pulmonary vascularity without cardiomegaly (but variable): "T" lesions (excluding Tetrology of Fallot): Transposition of the great arteries. Truncus arteriosus. Tricuspid atresia. Total anomalous pumonary venous return (TAPVR). Single ("Tingle") venticle, and variants including double outlet left ventricle and double outlet right ventricle.

Answer 22

Hypoplastic left heart (HLH) syndrome represents a spectrum of congenital heart anomalies characterized by underdevelopment of any part of the left heart including left atrium, mitral valve, left ventricle, aortic valve, or aorta. Survival is dependent on a patent ductus arteriosis with a resultant right to left shunting to supply the systemic circulation. Immediately after birth, the ductus arteriosus remains patent and pulmonary arterial resistance remains high, so blood continues to flow to the systemic circulation. After a few days, however, the ductus begins to close and pulmonary arterial resistance falls, leading to cardiogenic shock without operative management. The neonatal chest radiograph in HLH is usually normal, but HLH is classified as a "pulmonary edema" lesion. With a patent ductus and high pulmonary vascular resistance, the pulmonary blood flow is in the normal range, but as pulmonary resistance decreases, pulmonary blood flow increases. As the ductus closes, blood clearance from the lungs is delayed and pulmonary edema may result. Note that despite the left heart hypoplasia, the heart does not appear small on imaging. The surgical treatment of hypoplastic left heart is the Norwood procedure, performed in three sequential stages. A staged repair is necessary since the high pulmonary vascular resistance in the neonatal period precludes immediate definitive repair. Stage 1: The first stage of the Norwood procedure has three main components. First, the right ventricle is redirected to supply the systemic circulation, by reconstructing the aorta using the main pulmonary artery (Damus-Kaye-Stansel procedure). Second, the atrial septum is excised and the PDA is ligated, to redirect pulmonary venous return to the right heart via the atrial septal defect. Third, pulmonary arterial circulation is provided via a modified Blalock-Taussig shunt (BTS), which connects the right subclavian artery to the right pulmonary artery via a prosthetic graft. This stage is performed within the first few days of life. Stage 2: The BTS is replaced with a bidirectional Glenn (BDG) shunt, where the SVC is connected to the right pulmonary artery. This procedure is performed once pulmonary arterial resistance has fallen to normal levels, approximately 3-6 months after stage 1. The goal of stage 2 is to begin to separate systemic and pulmonary circulations. Stage 3: A modified Fontan is performed once the patient cannot supply adequate oxygenated blood to the systemic circulation. In this procedure, a tunneled conduit connects the IVC to the pulmonary artery. The SVC continues to empty into the right pulmonary artery via the BDG constructed into stage 2.

Answer 23

The two most common lesions to cause neonatal CHF are vein of Galen malformation and hepatic hemangioendothelioma.

Answer 24

Aortic coarctation may cause CHF in infants due to left ventricular obstruction, leading to cardiomegaly and increased pulmonary venous flow.

Answer 25

It is rare for shunt lesions to present in the neonatal period because pulmonary vascular resistance is high and left to right shunting is limited. In long-standing shunting, progressive volume overload causes the typical "shunt" vascularity (very prominent distince pulmonary arteries without the haziness of pulmonary edema) and cardiomegaly

Answer 26

Although atrial septal defect (ASD) is a common intracardiac left-to-right shunt, it is rarely diagnosed in infants or young children. ASD usually presents in later childhood or early adulthood, twice as commonly in females. Although most are an isolated abnormality, ASD may rarely be associated with syndromes, such as Holt-Oram (ASD and upper extremity bone deformities, including absence or hypoplasia of the thumb). Ostium secundum ASD is the most common type of ASD (accounting for 75% of cases), caused by incomplete covering of the ostium secundum by the septum secundum. Ostium primum ASD is the second most common type of ASD (15% of cases), caused by incomplete fusion of the septum primum to the endocardial cushion. Sinus venosus ASD occurs either near the superior vena cava of inferior vena cava. Although only accounting for 10% of ASDs, sinus venosus ASD is important to remember because of its association with anomalous pulmonary venous drainage. An ASD causes right heart volume overload. The left atrium is usually normal because blood is decompressed from the left atrium to the right atrium during both systole and diastole. However, if mitral regurgitation is present, secondary left atrial enlargement may result. Initially, the right atrium enlarges, followed by right ventricular enlargement (which may be visible on the lateral radiograph as filling of the retrosternal clear space). In late-stage disease the pulmonary artery also becomes enlarged. Shunt vascularity is usually present on radiography by the time the lesion is symptomatic. Treatment is ASD closure, typically with an Amplatzer or similar device.

Answer 27

Ventricular septal defect (VSD) is typically diagnosed earlier than ASD, with many children presenting after the first month of life as pulmonary vascular resistance falls. A VSD may occur in the membranous (70%) or muscular intraventricular septum. VSD primarily causes dilation of the left heart. Left-to-right shunting occurs in systole, causing volume overload of the left heart and resulting in left atrial and left ventricular dilation. Imaging findings are variable, depending on the size of the VSD. The classic imaging findings of shunt vascularity and cardiomegaly typically take a few years to develop, although there may be mild cardiomegaly and increased pulmonary vascular flow shortly after birth. The left atrium is often enlarged, which may splay the main stem bronchi at the carina. If unrepaired, Eisenmenger syndrome may develop, which represents pulmonary hypertension and reversal of the shunt direction. Eisenmenger syndrome is rare as most patients undergo surgery before pulmonary flow reversal occurs.

Answer 28

The ductus arteriosus is a normal vascular structure of the fetal circulation, connecting the proximal left pulmonary artery to the descending aorta. The ductus normally closes wihtin the first days of life. A patent ductus arteriosus (PDA) results in a persistent left-to-right shunt. PDA is much more common in premature infants, thought to be due to the presence of fetal prostaglandins, which inhibit closure of the ductus. A small PDA is usually asymptomatic. A large PDA may produce a characteristic machine-like murmur and cause CHF in infancy. The classic clinical presentation of PDA is a premature infant who develops radiographic evidence of CHF at 7-10 days of life, as pulmonary vascular reistance begins to fall. Treatment of PDA is medical (indomethacin) or surgical (clip placement). Eisenmenger syndrome may develop if untreated.

Answer 29

Endocardial cushion defects, also known as AV canal defects, encompass a spectrum of abnormalities including ostium primum ASD, VSD, and mitral or tricuspid anomalies. Endocardial cushion defects are strongly associated with trisomy 21. The primitive endocardial cushion is responsible for the formation of several structures in fetal development, including: Posterior and membranous ventricular septum. Anterior leaflet of the mitral valve. Septal leaflet of tricuspid valve. Responsible for closure of the ostium primum.

Answer 30

Ebstein anomaly is a severe malformation of the tricuspid valve characterized by apical displacement of the septal and posteroinferior leaflets, resulting in obstruction of the pulmonic valve and right venticular outlfow tract obstruction. These changes lead to morphologic "atrialization" of the RV. An ASD is always present. Imaging shows a huge heart, with massive right atrial enlargement and decreased pulmonary vascularity. The classic description for Ebstein anomaly is a box-shaped heart.

Answer 31

Pulmonary atresia with intact ventricular septum appears identical to Ebstein anomaly on radiography, with massive right atrial enlargement and decreased pulmonary blood flow. Because the lack of VSD markedly reduces blood flow to the lungs, pulmonary blood flow depends on a left to right shunt, such as a patent ductus. Pulmonary atresia with intact ventricular septum is completely different from pulmonary atresia with a VSD, which is in the spectrum of tetralogy of Fallot and most commonly has a normal-sized heart.

Answer 32

The four components of ToF are: 1. Right ventricular outlfow tract obstruction. 2. Right venticular hypertrophy. 3. VSD. 4. Aorta is "over-riding" the VSD. (A variation of ToF is the pentaology of Fallot, which includes an ASD) The degree of cyanosis depends on the degree of right ventricular outflow tract obstruction. Tetraology of Fallot (ToF) is the most common cyanotic heart disease of children and adults. ToF is associated with DiGeorge syndrome (absence of thymus and parathyroids, causing hypocalcemia), VACTERL, and trisomy 21. Classic radiographic findings of ToF are a boot-shaped heart (cardiac apex uplifted by RV hypertrophy, although the heart is normal in size) and decreased pulmonary vascularity. 25% of cases of ToF have a right-sided aortic arch. Surgical repair involves closure of VSD and opening of right ventricular outflow tract obstruction, which is usually performed in infancy. Pulmonary atresia with a VSD is a severe form of ToF.

Answer 33

In transposition of the great arteries (TGA), the right ventricle pumps blood to the aorta and the left ventricle pumps blood to the pulmonary arteries. TGA is the most common cause of cyanotic heart disease in newborns. Since the atria and ventricles are properly paired but the ventricles pump to the wrong great vessels, this configuration is termed atrioventicular concordance and ventriculoarterial discordance. The "strict" form of TGA is incompatible with life: There must be a site for admixture, either ASD, VSD, PDA, or a combination of left-to-right shunts. Prenatal ultrasound diagnosis of TGA requires evaluation of the short- or long-axis of the great vessels. TGA is usually inapparent on a four-chamber view. Sonographic diagnosis shows the aorta anterior to the heart and the great vessels exiting the heart in parallel (rather than crossing in the normal fashion). The classic radiographic findings of TGA are an "egg-on-a-string" appearance to the heart with a narrow mediastinal waist (caused by the configuration of the great vessels and thymic involution secondary to stress), lack of main pulmonary artery bulge, and parallel course of the aorta and PA. Although described in the literature, the "egg-on-a-string" appearance is uncommonly seen. A more typical radiographic appearance of TGA is a slightly narrow mediastinum and increased pulmonary vascularture; however, the radiographic picture can be varied depending on the nature of the coexisting shunt. A right aortic arch is seen in 5%. Surgical treatment is the arterial switch (Jatene) procedure, which swaps the aorta and pulmonary artery, and relocates the coronary arteries to the neo-aorta.

Answer 34

Tricuspid atresia is absence of the tricuspid valve, which may have a variable appearance depending on the size of the associated VSD. Small VSD: Normal size heart, with decreased pulmonary vasculature. Large VSD: Enlarged heart with increased pulmonary flow.

Answer 35

In truncus arteriosus, a single great artery arises from the base of the heart to supply the systemic, pulmonary, and coronary circulations. The single great artery usually over-rides a VSD. Truncus arteriosus is the most common type of congenital heart disease to have a right arch (21-36% of cases) The classic radiograph appearance is cardiomegaly, narrow mediastinum, and pulmonary edema.

Answer 36

In total anomalous pulmonary venous return (TAPVR), all pulmonary veins connect anomalously to the systemic venous circulation instead of draining into the left atrium. There is an obligate interatrial right-to-left communication enabling blood to reach the left heart, typically an ASD. Classification of TAPVR is based on the position of the venous drainage relative to the heart: Supracardiac (50%): Anomalous return is at or above the level of the SVC. The common confluence of the pulmonary veins drains into the let inominate vein via a vertical vein. Chest radiograph shows the characteristic snowman sign, with the dilated vertical vein making up the left border of the snowman. The snowman sign is seen in older patients without pulmonary venous obstruction. Cardiac (20%): Anomalous drainage is into the coronary sinus or right atrium. Infracardiac (20%): The anomalous drainage passes through the diaphragm via the esophageal hiatus and then drains into the hepatic IVC, hepatic vein, or portal venous system. Mixed (20%): Anomalous venous drainage is a combination of the above types. Clinical and radiographic findings depend on the degree of pulmonary venous obstruction and admixture. A typical radiographic appearance of obstructed TAPVR appearance is a normal-sized heart and pulmonary edema in an infant.

Answer 37

There are multiple variations of the single ventricle anomaly, which are all characterized by arteriovenous admixture at the level of a shared monoventricle. Double outlet right ventricle (DORV) can be considered a form of a single ventricle.

Answer 38

Aortic coarctation is congenital focal narrowing of the aorta in the region of the ductus arteriosus. It may be preductal (proximal to the ductus), periductal, or postductal. The preductal form may cause congestive heart failure (CHF) in infants due to left ventricular obstruction. In contrast, the juxtaductal, or postductal variants present later in life in the teenage or early adult years as upper extremity hypertension. Aortic coarctation is associated with bicuspid aortic valve, which may become stenotic and cause post-stenotic aortic dilation proximal ot the site of coarctation. Aortic coarctation is associated with Turner syndrome (XO). In infants, aortic coarctation may produce acyanotic (CHF). In adults, the classic radiographic finding is the 3 sign representing the contour of the coarcted aorta in the left upper mediastinum. Although rib notching is described as a classic finding, this is rarely seen.

Answer 39

Rhabdomyoma is the most common cardiac tumor, and primarily affects babies under 1 year old with tuberous sclerosis. Rhabdomyoma is the earliest sign of tuberous sclerosis that can be diagnosed in utero. Rhabdomyoma has a varied clinical presentation, including arrhythmia and obstruction. The most common radiographic appearance of rhabdomyoma is cardiomegaly. Pulmonary vascularture is variable.

Answer 40

Cardiac or pericardial teratoma is the second most common cardiac tumor detected in utero. A common location is attached to the root of the pulmonary artery and aorta. Teratoma may cause pleural effusion when arising from the pericardium. Pericardial teratoma is one of the primary causes of massive perinatal pericardial effusion, with potential for tamponade.

Answer 41

Fibroma is a rare, benign cardiac tumor of infancy and early childhood, arising from fibroblasts and myofibroblasts. Fibroma has a similar clinical presentation to rhabdomyoma, with rhythm disturbances and outflow obstruction. The interventricular septum is the most common site of origin, where a fibroma is especially likely to cause arrhythmia due to disruption of the conduction system. Cardiomegaly is the most common imaging finding.

Answer 42

Similar to teratoma, neonatal cardiac hemangioma is also associated with massive pericardial effusion.

Answer 43

Necrotizing enterocolitis (NEC) affects pre-term infants and is thought to be caused by a combination of infection and ischemia related to feeding. Mortality can be up to 30%. Although NEC is typically seen in premature infants, it may also occur in term infants with congenital heart disease, on immunosuppresion, or with umbilca venous catheter. The initial radiographic findings include bowel thickening and fixed distension of a loop of bowel over serial exams. NEC most commonly involves the ileum and right colon in the right lower quadrant. Later in disease, pneumatosis, protal venous gas, or pneumoperitoneum related to bowel perforation may be present. Pneumoperitoneum can be difficult to detect on supine radiographs. One should always draw an imaginary line across the liver from right to left - if the liver gets darker then one should consider pneumoperitoneum. The football sign represents air outlining the falciform ligament in pneumoperitoneum. Early NEC can be treated medically (TPN, antibiotics, and cessation of oral feeding). If pneumoperitoneum is present, emergent surgery is generally required; however, bowel-sparing percutaneous drainage is an emerging option in some cases. Once the baby recovers, contrast enema can evaluate for stricture, which is the most common delayed complication of NEC.

Answer 44

Hypertrophic pyloric stenosis (HPS) is mucosal hypertrophy of the pylorus, which classically causes progressive, projectile, non-bilious emesis in firstborn males (females are affected three times less commonly) at 2-12 weeks old. HPS is the most common surgically treated ause of vomiting in infants. Although there is a genetic association, most cases are sporadic and idiopathic. A suggestive plain film finding is the caterpillar sign, which describes the undulating contour of the gastric wall peristalsing against an obstructed pylorus. Ultrasound criteria vary by institution; typical criteria for diagnosis include wall thickness \>/=4 mm (measuring from echogenic mucosa to echogenic serosa) and a channel length \>/=16 mm. Positive cases will not show feeds passing through the pylorus. An important pitfall to be aware of is imaging a collapsed, normal gastric antrum. Treatment is pyloroplasty, with IV fluid and electrolyte replacement while waiting for surgery. The main differental consideration is pylorospasm, for which close clinical follow-up is recommended. Visualization of gastric contents passing through the pylorus is suggestive of pylorospasm and pylorospasm generally features a normal-appearing pylorus.

Answer 45

Appendicitis is the most common reason to perform abdominal surgery in a child. Abdominal pain is usually present, but the clinical presentation in children may be atypical and diagnosis can be challenging. Appendicitis is rare in infants. Ultrasound is the first test of choice for evaluation of suspected appendicitis in children. A swollen (\>6 mm), incompressible, blind-ending tubular structure in the right lower quadrant is a typical imaging appearance. An echogenic appendicolith and increased echogenicity of the surrounding mesenteric fat may also be seen. CT can be used as a problem-solving modality, for instance if the appendix is not visualized on ultrasound with clinical suspicion for appendicitis. The CT findings of appendicitis in children are identical to those in adults.

Answer 46

Malrotation is the failure of normal rotation of the bowel during embryogenesis, which predisposes to volvulus due to abnormal mesenteric fixation. Volvulus is a true surgical emergency, with a high mortality rate due to bowel ischemia if the diagnosis is delayed. Most infants with volvulus present with neonatal bilious emesis. Although bilious emesis may be due to several entities including non-obstructive gastroenteritis, malrotation with volvulus must be ruled out emergently with an upper GI. It is possible to have malrotation without volvulus, and symptoms without volvulus can be vague or nonspecific, including feeding intolerance, cyclic vomiting, and malabsorption. Therefore, it is essential to consider malrotation in a child with abdominal symptoms. 75% of infants with malrotation present within the first month of life and 90% become symptomatic within one year. In order to diagnose malrotation (with or without volvulus), it is important to understand the anatomy of the normal upper gastrointestinal tract. In normal embryologic development, the bowel rotates 270 degrees counterclockwise around the superior mesenteric artery, causing the characteristic retroperitoneal course of the duodenum. The most important anatomy to demonstrate on every upper GI is the C-sweep of the duodenum and position of the duodeno-jejunal junction (DJJ). The normal DJJ is evaluated on the frontal view and should be to the left of the left-sided pedicle at the level of the duodenal bulb (L1). On abdominal radiography, midgut volvulus most commonly appears as multiple dilated loops of bowel. Less commonly, midgut volvulus may produce a double bubble sign from duodenal obstruction. However, plain films can also be entirely normal in the setting of malrotation and vomiting. The classic upper GI finding of midgut volvulus is the corkscrew appearance of twisted bowel. In the absence of midgut volvulus, the diagnosis of malrotation can be challenging. The DJJ is a mobile structure and can be manipulated during the upper GI exam. Even experienced pediatric radiologists may occasionally disagree. Some clues to the presence of malrotation include: DJJ inferior to the duodenal bulb. DJJ to the right of the left pedicle. Cecum either more midline than typical or frankly in the left lower quadrant. On CT or US: Inversion of normal relationship of SMA and SMV (normally SMV ot the right of the SMA). Color Doppler ultrasound or CT studies of the twisted mesenteric vessels demonstrate the whirlpool sign. The treatment of malrotation with volvulus is the Ladd procedure: Volvulus reduction, resection of necrotic bowel, and lysis of mesenteric adhesions ("Ladd" bands). The small and large bowel are separated, with the small bowel positioned primarily on the patient's right and the large bowel on the patient's left. Appendectomy may be performed.

Answer 47

Intussusception is caused by two telescoping bowel loops prolapsing into each other. The most common location is ileocolic where the ileum prolapses into the colon. Intussusception is common and classically presents with colicky abdominal pain, "currant jelly stool", an a palpable right lower quadrant abdominal mass. Most children between 3 months and 3.5 years old have idiopathic intussusceptions caused by lymphoid tissue from a preceding viral illness. In contrast, both newborns and children older than 3.5 years have a pathologic lead point, which may be an intestinal polyp, Meckel diverticulum (infants), or lymphoma (children). A transient, asymptomatic, incidental, short-segment intussusception in older children or adults seen on CT performed for another reason is likely clinically insignificant. Radiographs are nonspecific, but may show a soft tissue masss in the right lower quadrant. Ultrasound is the primary modality fo diagnosis, which shows a characteristic target or pseudokidney sign with alternating layers of bowel wall and mesenteric fat. The differential diagnosis of bloody stool and thick-walled bowel on ultrasound includes intussesception, colitis, and much less commonly intramural hematoma (e.g. due to trauma or Henoch-Schonlein purpura). The first line treatment is reduction with an air or contrast enema. The choice of air or contrast varies by institution, but air enemas are generally considered safer. Contraindications to pneumatic reduction include free air, peritoneal signs, and septic shock.

Answer 48

Esophageal atresia is a blind-ending esophagus caused by faulty embryologic separation of the primitive trachea from the esophagus. In embryologic development, the trachea and esophagus initially form as one structure. Esophageal atresia is almost always associated with tracheoesphageal fistula (TEF). 50% of patients with TEF have associated anomalies, most commonly the VACTERL association: Vertebral segmentation anomalies. Anal atresia. Cardiac anomalies. TracheoEsophageal fistula. Renal anomalies. Limb (radial ray) anomalies. A classic radiographic finding of the most common A type (82%) TEF (with proximal esophageal atresia and a distal tracheoesophageal fistula) shows an NG tube terminating in the mid esophagus with air-filled bowel from a distal TEF. The much less common B type (8%) may present with a gasless abdomen, due to esophageal atresia, but with upper esophageal TEF. This type may present later in childhood with recurrent aspiration. Esophageal atresia should be considered in utero if there is polyhydramnios and lack of visualization of the stomach. TEF is often associated with tracheal anomalies including tracheomalacia and bronchus suis (right upper lobe bronchus arising directly from trachea).

Answer 49

Gastric atresia represents congenital obstruction of the distal stomach. Gastric atresia causes non-bilious vomiting. In contrast to hypertrophic pyloric stenosis, the vomiting does not get progressively worse. A diagnostic imaging finding is the single bubble, with a large bubble of air (or contrast) in the proximal stomach. A less severe variant is a nonobstructive antral web.

Answer 50

Neonatal bowel obstruction, occurring within the first 24-48 hours of life, is a completely different entity from childhood or adult obstruction, with different workup and different etiologies. Unlike in adults, CT pjlays no role in the workup of neonatal bowel obstruction. In the neonate, small bowel cannot be distinguished from large bowel based on location or size of the bowel loops. When loops of distended bowel are seen and obstruction is suspected, it is possible to divide the differential into proximal/high obstruction (proximal to the distal jejunum) or distal/low obstruction (distal to the distal jejunum) based solely on the number of dilated loops seen. All cases of proximal obstruction are surgical. The goal of imaging is to differentiate surgical from non-surgical causes of distal obstruction. If the initial radiograph does not provide a definitive diagnosis, the imaging test of choice for a proximal obstruction is typically an upper GI. Midgut volvulus must be ruled out. A patient with characteristic clinical and imaging findings of duodenal atresia can be diagnosed on radiograph alone. For instance a baby with known Down syndrome and a double bubble on radiograph is considered diagnostic of duodenal atresia. Subsequent to the initial radiograph, the imaging test of choice for a distal obstruction is a contrast enema, which can be both diagnostic and therapeutic. A neonatal contrast enema is performed with a relatively low-osmolar, water-soluble contrast material, such as 17% solution of iothalamate meglumine (400mOsm/kg water).

Answer 51

All causes of congenital proximal bowel obstruction are surgical. the primary purpose of an upper GI is to distinguish between midgut volvulus (requiring emergent surgery) and the atresias, which require a non-emergent repair.

Answer 52

During embryogenesis, the duodenum forms as a solid tube. Lack of recanalization causes the spectrum of diseases ranging from duodenal atresia (most severe; complete lack of recanalization) to duodenal stenosis (least severe; partial recanalization). A less severe variant, the duodenal web, allows liquids to pass, but causes the windsock deformity after the child begins to eat solid foods, which gets stuck in the web. Even a complete atresia does not preclude distal bowel gas. In the presence of a rare congenital bifid common bile duct, bowel can travel through the ampulla of Vater and enter the distal small bowel. Duodenal anomalies are associated with additional abnormalities in 50% of cases, most commonly Down syndrome; 30% of babies with duodenal atresia have Down syndrome. Other associated anomalies include: VACTERL. Shunt vascularity cardiac lesions (ASD, VSD, PDA, and endocardial cushion defect). Malrotation. Annular pancreas, which is seen in 20% of babies with duodenal atresia. The classic radiographic appearance of duodenal atresia is the double bubble sign caused by dilation of both the stomach and the proximal duodenum, without distal bowel gas. A patient with a double bubble and no distal bowel gas can be presumed to have duodenal atresia. If distal bowel gas is present with a double bubble sign, the differential diagnosis includes midgut volvulus, annular pancreas (pancreas wraps around the duodenum), and the less severe variants of duodenal atresia including duodenal stenosis and web.

Answer 53

Unlike duodenal atresia, jejunal atresia is most commonly caused by an in-utero vascular insult. Jejunal atresia is more common than stenosis. The triple bubble has been described to represent proximal jejunal atresia, which may present on radiography as dilated stomach, duodenum, and proximal jejunum.

Answer 54

A contrast enema is performed to differentiate surgical causes (distal atresias and Hirschsprung disease) from medical causes (meconium ileus and functional immaturity) of low/distal bowel obstruction. When performing a contrast enema, isotonic or mildy hypertonic water-soluble contrast is used, such as 17% solution of cysto-Conray II (400 mOsm). High osmolar contrast may cause fluid shifts and resultant destabilization of the patient.

Answer 55

Microcolon is a colon of abnormally small caliber (typically \<1 cm), secondary to disuse. A relatively distal obstruction is necessary to develop a microcolon, as the succus entericus secreted by the proximal bowel prevents microcolon. The two most common causes of microcolon are meconium ileus and ileal atresia.

Answer 56

Meconium ileus causes bowel obstruction from inspissated meconium in the distal ileum and colon. Meconium ileus may be complicated by perforation and resultant meconium peritonitis, which can cause abdominal and scrotal calcifications. Meconium ileus is the earliest manifestation of cystic fibrosis: Almost 100% of babies with meconium ileus have cystic fibrosis, while ~10% of babies with cystic fibrosis have meconium ileus. The classic radiographic appearance of meconium ileus is a distal obstruction (multiple loops of dilated bowel), which soap-bubble lucencies in the right lower quadrant. Contrast enema shows a microcolon (meconium ileus has the smallest of all microcolons) with a distended ileum containing multiple rounded filling defects representing inspissated meconium. Meconium ileus is both diagnosed and treated with therapeutic water-soluble gastrografin enema, which functions to loosen the inspissated meconium. It often takes multiple attempts to fully clean out the meconium, and carefully increasing the contrast osmolality may be helpful. Uncommonly, resistant cases may need to be treated surgically.

Answer 57

Atresia of the ileum or colon features a microcolon distal to the atretic segment. Colonic atresia is rare. Unlike meconium ileus, ileal and colonic atresia demonstrate an abrupt cutoff at the site of atresia, and there are no filling defects within the bowel.

Answer 58

Small left colon, also known as functional immaturity of the colon or meconium plug syndrome, is the most common diagnosis in neonates who fail to pass meconium. Small left colon is caused by temporary functional immaturity of the colonic ganglion cells, which causes the distal colon to have abnormal motility right after birth. Small left colon is seen more commonly in pre-term neonates, noenates born to mothers who received magnesium for (pre)eclampsia, and infants born to diabetic mothers. Infants with small left colon are almost always otherwise normal. In contrast to meconium ileus, small left colon is not a cause of microcolon. Small left colon is not associated with cystic fibrosis/meconium ileus despite the name of "meconium plug syndrome". The imaging appearance on an abdominal radiograph is of a distal obstructive pattern. Contrast enema shows a small left colon, typically with a discrete transition in caliber at the splenic flexure. There may be filling defects within the small left colon representing meconium plugs. Similar to meconium ileus, water-soluble enema is diagnostic and therapeutic, and small left colon resolves with conservative therapy. The primary differential consideration is Hirschsprung disease with a transition at the splenic flexure. In contrast to small left colon, Hirschsprung disease would not feature a distensible rectum and would not resolve after an enema treatment.

Answer 59

Hirschsprung disease is aganglionosis of the distal bowel, resulting in lack of relaxivity of the involved bowel. Hirschsprung disease is caused by arrest of the normal craniocaudal (proximal-to-distal) migration of vagal neural crest cells ot the distal bowel wall. The anus is therefore always affected and the involved bowel is continuous distal to proximal. Hirschsprung disease ranges in severity from isolated internal anal sphincter involvement (ultrashort segment) to involvement of the entire colon (very rare, approximately 1-3% of cases, and typically genetic.) Up to one third of cases of Hirschsprung develop a form of enterocolitis similar to necrotizing enterocolitis, with toxic megacolon being the fulminant form. It is therefore important to consider Hirschsprung in a neonate with bowel obstruction and colitis. There are multiple congenital anomalies associated with Hirschsprung disease. Five percent have trisomy 21, but there is much less of an association with Down syndrome compared to duodenal atresia. Radiography of Hirschprung disease shows a distal bowel obstruction pattern. Contrast enema typically shows a distal bowel obstruction pattern. Contrast enema typically shows a cone-shaped transition zone at the junction of the spastic, narrowed distal colon and the dilated proximal colon, which is best seen on the lateral view. The rectum normally has a larger diameter than the sigmoid. When Hirschsprung involves the rectum, the rectum will be in spasm and the sigmoid will be dilated, causing an abnormal rectum:sigmoid ration less than 1 (i.e., rectum is smaller than the sigmoid). The initial contrast enema may be normal in neonates with ultrashort segment involvement. In contrast to functional immaturity of the colon, Hirschsprung disease tends to causea tapered, rather than an abrupt, transition zone. Definitive diagnosis is with suction biopsy of the bowel wall. Treatment is surgical.

Answer 60

Megacystis microcolon intestinal hypoperistalsis syndrome is a rare congenital loss of bladder and smooth muscle function causing absent intestinal peristalsis, microcolon, and distended non-obstructed urinary bladder. It is usually fatal.

Answer 61

The etiologies and imaging of childhood bowel obstruction overlap with those of adults. Adult bowel obstruction is most commonly caused by adhesions and hernia, both of which may also cause obstruction in a child. The most common causes of childhood bowel obstruction can be remembered with the mnemonic AAIMM (appendicitis, adhesions, internal/inguinal hernia, intussusception, Meckel's, and malrotation). Most causes of childhood obstruction are treated surgically.

Answer 62

Appendicitis is one of the more common causes of ileus or partial bowel obstruction in children.

Answer 63

Indirect inguinal hernia is due to a patent processus vaginalis, which maintains a peritoneal communication to the scrotum via the inguinal ring. Imaging of an inguinal hernia causing obstruction shows bowel in the inguinal canal or scrotum. There is risk of bowel incarceration in an irreducible hernia.

Answer 64

Crohn disease may be a cause of bowel obstruction. Up to 30% of newly diagnosed Crohn disease presents in the pediatric population.

Answer 65

Imperforate anus is a clinical diagnosis, but radiology plays a role to evaluate the level of the obstruction, which is classified as high or low in relation to the puborectalis sling. A high lesion (above the puborectalis sling) is associated with genitourinary-rectal fistula, lumbosacral anomalies or VACTERL association, and requires a more ocmplex treatment. Males may have a fistula between the rectum and posterior urethra or bladder. Females may have a rectovaginal fistula. In either sex, treatment is initial colostomy followed by definitive repair. A low lesion (below the puborectalis sling) is associated with perineal fistula and is treated with single-stage perineal anoplasty. The determination of high or low lesion is usually made clinically, based on passage of meconium, and is dependent on sex. In males, if meconium is passed in urine -\> high lesion. In females, if meconium is passed in the vagina and a fistula is not visualized -\> high lesion. Low lesions cause distal vaginal fistulas, which can be visualized by physical exam. Previously, prone radiographs were used to determine if a lesion was high or low; however, infracoccygeal ultrasound is thought to be a more accurate method to determine the level of the imperforate anus.

Answer 66

In contrast to the unconjugated hyperbilirubinemia of the benign and self-limited physiologic jaundice of the newborn, conjugated hyperbilirubinemia is never normal and is due to hepatic or biliary dysfunction. There are innumerable causes of conjugated hyperbilirubinemia, including biliary atresia, Alagille syndrome, bile acid synthetic defects, metabolic disease, alpha-1-antritrypsin deficiency, and infectious etiologies. The goal of imaging is to differentiate between biliary atresia (approximately 25% of neonatal conjugated hyperbilirubinemia) and "neonatal hepatitis", which is a wastebasket diagnoses for all other causes combined. Tc-99m-HIDA hepatobiliary scintigraphy is the test of choice to distinguish between these two entities. Patients may be premedicated with 5 days of phenobarbital to stimulate hepatocyte activity prior to hepatobiliary scintigraphy, although this varies by institution. The HIDA agent is actively transported into the hepatocyte and excreted (not conjugated) into the bile. Biliary atresia requires prompt repair to prevent irreversible liver damage. The treatment of neonatal hepatitis is nonsurgical.

Answer 67

Biliary atresia is characterized by an obliterative cholangiopathy that affects the intra- and extra-hepatic bile ducts, leading to obstructive (conjugated) jaundice. Biliary atresia leads to progressive cirrhosis and death in early childhood if untreated. Hepatobiliary scintigraphy shows normal hepatic tracer uptake and clearance but no excretion into the small bowel. Ultrasound is not able to distinguish between biliary atresia and neonatal hepatitis. The absence of a gallbladder on ultrasound is suggestive of biliary atresia, but a gallbladder is seen in 20% of cases. Treatment of biliary atresia is the Kasai portoenterostomy, a palliative procedure. The entire extrahepatic biliary tree is excised and a jejunal Roux loop is anastomosed to the cut surface of the liver capsule. 80% of children with a successful surgery survive 10 years, at which point a liver transplant is necessary.

Answer 68

Hepatobiliary scintigraphy shows poor hepatic excretion, delayed hepatic clearance (beyond 12 hours), and variable bowel excretion. Biliary atresia can be effectively rule out if there is any excretion into the GI tract.

Answer 69

Primary pediatric tumors may be classified pathologically as epithelial (hepatocyte-derived) or mesenchymal, with benign and malignant tumors in each category. Liver metastases may be seen in the setting of neuroblastoma, Wilms tumor, sarcoma, and Burkitt lymphoma. It is usually possible to narrow the differential based on imaging appearance (cystic or solid), age of the patient, and tumor markers (AFP and endothelial growth factor). Benign epithelial lesions also seen in adults, including focal nodular hyperplasia and adenoma.

Answer 70

Mesenchymal hamartoma is a benign, multicystic, hamartomatous lesion, which contains malformed bile ducts, portal vein fragments, and often extramedullary hematopoiesis. It is considered a developmental anomaly rather than a neoplasm. Most children present in the neonatal period with an enlarging abdominal mass, with 80% diagnosed by 2 years of age. In contrast to hepatoblastoma, tumor markers are not elevated. Imaging of mesenchymal hamartoma typiaclly shows a large, multicystic, abdominal mass. The cysts can be of various sizes, can contain debris, and can be divided by septae of variable thickness. Hemorrhage and calcification are rare. Occasionally, the cysts may be so small the the mass appears solid. When large, the mass may displace vasculature. Surgical resection is almost always curative.

Answer 71

Choledochal cysts (including Caroli disease) represent saccular or fusiform dilation of bile ducts, which may be segmental or diffuse. The Todani classification of choledochal cysts is discussed further in the gastrointestinal imaging section.

Answer 72

Gallbladder hydrops is a pathologically distended gallbladder, usually associated with infection or a systemic inflammatory process such as Kawasaki disease.

Answer 73

Pediatric vascular anomalies can be divided into vascular neoplasms and vascular malformations, where neoplasms feature new cell growth and malformations feature disorganized vasculature without cell growth. Pediatric vascular anomalies can also be classified physiologically as high-flow or low-flow lesions. High-flow vascular malformations include arteriovenous malformations (AVM) and arteriovenous fistulas (AVF), while low-flow vascular malformations include venous malformations and lymphatic malformations. The term "hemangioma" is a common source of confusion. In particular, the term "hepatic hemangioma" is often used to describe multiple unrelated vascular lesions including infantile hemangioma, potentially malignant hemangioendotheliomas, and benign venous malformations. The common adult hepatic "hemangioma" is actually a venous malformation in the classification above. Similarly, the soft tissue "hemangiomas" of Maffucci syndrome are also venous malformations. Infantile hemangioma and hemangioendothelioma, are high-flow vascular neoplasms. Hemangioendotheliomas have the potential to metastasize.

Answer 74

Infantile hemangioma and hemangioendothelioma are related vascular neoplasms that are the most common vascular hepatic tumors and which may cause congestive heart failure in up to 25%. Tumor markers are not elevated. Infantile hemangioma is benign. While hemangioendothelioma is usually benign, it has the potential to metastasize. This text will use the term "infantile hemangioma" to include both of these entities. Infantile hemangioma is associated with Kasabach-Merrit syndrome, which is a syndrome of vascular neoplasm, hemolytic anemia, and consumptive coagulopathy. Infantile hemangioma may be focal, multifocal, or diffuse. Lesions are highly vascular, T2 hyperintense, and tend to enhance peripherally with delayed fill-in. There may be calcification, central necrosis, and hemorrhage. Angiography (which can be performed prior to embolization) classically shows an enlarged celiac artery, with a decreased caliber of the aorta distal to the celiac axis. Similar to cutaneous infantile hemangiomas, most hepatic infantile hemangiomas will spontaneously involute the first year of life, especially if GLUT-1 positive. The beta-blocker propranolol may accelerate involution. Surgery may be necessary for lesions causing CHF.

Answer 75

Hepatoblastoma is a malignant embryonal neoplasm that is the most common liver tumor of early childhood and the third most common childhood abdominal malignancy overall (third to neuroblastoma and Wilms tumor). Hepatoblastoma occurs in children slightly older than those affected by infantile hemangioma and mesenchymal hamartoma. Less than 10% of cases occur during the neonatal period. Hepatoblastoma is associated with several genetic anomalies and syndromes, including: Beckwith-Wiedemann (Q6 month screening ultrasound is performed). Familial adenomatous polyposis syndrome. Fetal alcohol syndrome. Alpha fetoprotein (AFP) is elevated. A classic radiograph finding of hepatoblastoma is right upper quadrant calcification. Cross-sectional imaging shows a heterogenous, predominantly solid, enhancing liver mass, which demonstrates a propensity for portal vein and hepatic vein invasion.

Answer 76

Similar to adults, hepatocellular carcinoma (HCC) is usually seen in the background of cirrhosis. Pediatric causes of cirrhosis include alpha-1-antitrypsin defiency, glycogen storage disease, tyrosinemia, biliary atresia, and chronic viral hepatitis. AFP (alpha fetoprotein) is elevated, similar to hepatoblastoma. Imaging is similar to adult HCC, appearing as a heterogenous hepatic mass with early arterial enhancement and rapid washout. SImilar to hepatoblastoma, HCC also commonly demonstrates venous invasion.

Answer 77

Undifferentiated embryonal sarcoma is a highly agressive mesenchymal neoplasm occuring in school-age children 6-10 years old. Unlike hepatoblastoma and HCC, AFP is negative.

Answer 78

Wilms tumor and neuroblastoma are common pediatric tumors with a propensity to metastatize to the liver.

Answer 79

Meckel diverticulum is an omphalomesenteric duct remnant. In young children, the most common manifestation of a Meckel diverticulum is gastrointestinal bleeding (if the Meckel conatins ectopic gastric mucosa). Less commonly, a Meckel may cause intussusception by acting as a lead point. In adults, small bowel obstruction is the most common complication of a Meckel diverticulum, followed by Meckel diverticulitis. The omphalomesenteric duct connects the fetal intestine to the yolk sac via the umbilicus. Incomplete regression of the duct leads to a spectrum of anomalies, ranging from an umbilico-ileal fistula (fecal drainage from the umbilicus) to a Meckel diverticulum. Meckel diverticulum is by far the most common anomaly (approximately 95%) caused by remnant of the omphalomesenteric duct. A Meckel diverticulum is located at the antimesenteric aspect of the distal ileum. Although there are often exceptions, the "rule of 2's" states that Meckel diverticula are present in 2% of the population, located 2 feet from the ileocecal valve, and become symptomatic before age 2. A Meckel diverticulum causing rectal bleeding can be diagnosed with a Tc-99m-pertechnetate scan. The scan is only positive if the Meckel contains ectopic gastric mucosa; however, these are the Meckels that are most likely to bleed. Approximately 50% of Meckels contain ectopic gastric (less commonly pancreatic) mucosa. On pertechnetate scan, uptake kinetics of the ectopic mucosa is equal to gastric mucosa.

Answer 80

Meconium aspiration causes respiratory distress in term neonates. Meconium ileus is the earliest manifestation of cystic fibrosis and only occurs in patients with cystic fibrosis. It causes a microcolon. Meconium plug syndrome (small left colon) is a self-limited cause of distal neonatal bowel obstruction. Unlike meconium ileus, meconium plug syndrome is not associated with cystic fibrosis, and is not a cause of microcolon. Meconium ileus-equivalent syndrome can be the presenting symptoms of previously undiagnosed cystic fibrosis, typically in an adolescent or young adult. Meconium ileus-equivalent syndrome clinically presents with recurrent abdominal pain and chronic constipation. Meconium peritonitis is caused by in-utero small bowel perforation and meconium spillage, resulting in peritonitis, secondary calcifications, and meconium pseudocyst formation.

Answer 81

Abdominal calcifications seen on radiography can be an important clue to the presence of underlying pathology, including: Meconium peritonitis. Several pediatric neoplasms may contain calcifications, including neuroblastoma, teratoma, and hepatoblastoma. Adrenal hemorrhage may cause calcification of the adrenal glands. Right upper quadrant calcifications can be seen with gallstones, hepatoblastoma, and hepatic TORCH infections (e.g., CMV and toxoplasmosis).

Answer 82

Vesicoureteral reflux (VUR) is abnormal retrograde reflux of urine from the bladder into the ureter, which predisposes to actue pyelonephritis, renal scarring, and irreversible loss of renal function. VUR can be primary (due to an abnormally short intravesicular portion of the distal ureter) or secondary (due to distal obstruction, such as from posterior urethral valves or neurogenic bladder). The typical imaging evaluation of a child with a febrile UTI is controversial and may involve renal ultrasound and voiding cystourethrogram (VCUG). Renal ultrasound is not sensitive for the detection of reflux, although some institutions perform ultrasound as a screening modality. Recent studies suggest that approximately 5% of children with a UTI and a normal ultrasound have VUR. Sibilings of patients diagnosed with reflux are typically screened with ultrasound: Up to 45% may have reflux, the majority being asymptomatic. The goal of any treatment of VUR is to prevent pyelonephritis and the resultant renal scarring, which can lead to irreversible loss of renal function. The treatment can be either medical (prophylactic antibiotics) or surgical, depending on the grade. Grades I-III are initially treated medically (prophylactic antibiotics). higher grade reflux is often treated surgically. Approximately 90% of grade I and II reflux will spontaneously regress after a few years. Grading of reflux is based on voiding cystourethrogram (VCUG): I: Reflux into ureter only, with normal urteral and calyceal morphology. II: Reflux into non-dilated renal calyces, with normal ureteral and calyceal morphology. III: Reflux into renal collecting system, with blunting of the calyces (loss of normal "spiky" appearance of calyces). IV: Reflux into moderately dilated ureter. V: Reflux into severely dilated and tortuous ureter. VCUG is often preferred as the initial study for evaluation of reflux because it provides anatomic details about the upper tract and also allows evaluation of the urethra. In boys, partial posterior urethral valves may be a cause of UTI. Two nuclear studies are often used for the evaluation and follow-up of reflux: Radionuclid cystogram (RNC) involves the instillation of approximately 1 mCi of Tc-99m-pertecnetate into the bladder through a catheter. RNC is the most sensitive test to evaluate for reflux. RNC is often used for follow-up of reflux once the anatomy is established by VCUG. RNC grading is 3 stage. RNC grade 1: Ureteral reflux only (VCUG I). RNC grade 2: Reflux reaches renal calyces (VCUG II-III). RNC grade 3: Ureteral dilation (VCUG IV-V). Tc-99m-DMSA renal scintigraphy (DMSA scan) is the gold standard for detection of renal cortical scarring.

Answer 83

A duplex collecting system contains two separate pelvicalyceal systems and two ureters. A duplex system may be of no clinical significance if the ureters fuse. However, if the ureters insert separately into the bladder, there is an increased risk of obstruction (in the upper pole moiety) and reflux (in the lower pole moiety), as described by the Weigert-Meyer rule. The Weigert-Meyer rule: In a duplicated system, the upper pole ureter inserts ectopically (inferomedially) into the bladder and is prone to obstruction, often due to a ureterocele. The lower pole ureter inserts orthotopically (normally) but is prone to reflux. Although hydronephrosis in an obstructed upper pole system would be apparent on ultrasound, a completely obstructed system may not be seen on VCUG at all since contrast cannot flow retrograde into the obstructed ureter. The drooping lilly sign is seen on VCUG where the "invisible" obstruced upper moiety compresses the refluxed contrast in the lower moiety collecting system. The differential diagnosis of a drooping lily is renal ptosis, which would be expected to show a normal number of calyces. In contras, the obstructed upper pole of the drooping lily has fewer calyces.

Answer 84

Uretopelvic junction (UPJ) obstruction is the most common cause of unilateral hydronephrosis in children. UPJ obstruction may be caused by an aberrant renal artery compressing the ureter aperistaltic segment of the ureter, or can be idiopathic.

Answer 85

Posterior urethral valves are the most common cause of congenital bladder outlet obstruction, caused by an obstructing web in the posterior (prostatic) urethra. Ultrasound shows dilation of the posterior (porstatic) urethra, a dilated and trabeculated bladder, and hydronephrosis. The appearance of the dilated posterior urethra and dilated bladder produces the characteristic keyhole appearance on ultrasound. The main differential consideration is prune belly syndrome, which would show dilation of the entire ureter rather than only the prostatic portion.

Answer 86

Prune belly syndrome is a congenital musclular disorder that affects teh abdominal wall musculature and the smooth muscles fo the entire urinary collecting system. Prune belly may be associated with cryptorchidism. The muscular defect leads to dilation of the entire collecting system, including the bladder and both ureters. In contrast to posterior urethral valves, the entire urethra is dilated.

Answer 87

A ureterocele is focal dilation of the distal ureter within the bladder wall, where the ureter infolds between the mucosal and muscular layers of the bladder wall. An ectopic ureterocele is almost always associated with ectopic insertion of the upper pole ureter in a duplicated system. A simple ureterocele is seen with an orthotopically (normally) inserting ureter. The typical ultrasound appearance of an ectopic ureterocele is a cystic lesion within the bladder wall, usually associated with hydroureter and hydronephrosis of an obstructed upper pole moiety in a duplex system. Ectopic ureterocels are almost always located inferior and medial ot the lower pole ureteral insertion site. VCUG typically shows the ureterocele as a rounded filling defect.

Answer 88

Hydronephrosis is the most common cystic abdominal mass in a neonate

Answer 89

Multicystic dysplastic kidney (MCDK) is the most common neonatal cystic renal mass, characterized by a progressive renal dysplasia thought to be a result of fetal ureinary obstruction. MCDK is typically unilateral, but bilateral abnormalities may be present in 20-30%. The natural progression of MCDK is gradual involution. It is thought that many adults with a solitary kidney may have had a previously undiagnosed, involuted MCDK. The risk of Wilms tumor in MCDK is controversial. Although an association between MCDK and Wilms tumor has been reported, there is no strong evidence to support a link. Imaging of MCDK shows a multicystic "mass" replacing the renal parenchyma. The cystic elements do not communicate with each other, which is in contrast to hydronephrosis.

Answer 90

An isolated simple renal cyst is rare in children. When seen, renal cysts are more likely to be syndromic, in association with tuberous sclerosis or von Hippel-Lindau. Tuberous sclerosis: In addition to renal cysts, patients may have: Renal angiomyolipomas, Cardiac rhabdomyomas, CNS cortical hamartomas, subependymal nodules, and subependymal giant cell astrocytoma. von Hippel-Lindau (VHL): In addition to renal cysts, patients have: Renal cell carcinoma (RCC): Up to 30% of VHL patients die from RCC, Adrenal pheochromocytoma, Pancreatic cysts, islet cell tumors, and serous cystadenomas, brain and spinal cord hemangioblastomas.

Answer 91

Multilocular cystic nephroma is a benign, multiseptated cystic neoplasm. It has a bimodal age distribution, seen in young bodysj age 3 months to 2 years and middle-aged women. Multilocular cystic nephroma is a multiseptated cystic renal mass with enhancing septa. Its appearance may mimic cystic Wilms tumor. A characteristic imaging finding is its propensity to herniate into the renal pelvis, causing hydronephrosis.

Answer 92

Autosomal dominant polycystic kidney disease (ADPKD) usually manifests in adulthood, although 50% develop some cysts within the first decade of life. ADPKD is associated with hepatic cysts and less commonly pancreatic cysts.

Answer 93

Autosomal recessive polycystic kidney disease (ARPKD) features tiny cysts that develop in infancy due to generalized dilation of the collecting tubules. The cysts are typically too small to be resolvable by imaging, porducing a characteristic appearance of bilaterally enlarged, echogenic kidneys. Earlier presentations have worse prognosis, with fetal diagnosis often causing severe oligohydramnios and pulmonary hypoplasia. ARPKD is associated with hepatic fibrosis, especially when ARPKD manifests later in childhood.

Answer 94

Wilms tumor is the most common childhood renal neoplasm. It typically affects children between 3 and 5 years of age. Wilms arises from persistent metanephric blasterna. Patients with increased risk for Wilms tumor are screened with regular ultrasound until school age, and include patients with: Becwith-Wiedemann syndrome (hemihypertrophy, macroglossia, omphalocele, neonatal hypoglycemia (due to insulin overproduction by pancreatic b-cells), and increased risk of childhood malignancies, including Wilms tumor and hepatoblastoma). WAGR syndrome (Wilms tumor, aniridia, genitourinary anomalies, and mental retardation). Horshoe kidney: Approximately 2x incidence of Wilms tumor. Trisomy 18. The classic imaging appearance of Wilms is a heterogenous, solid renal mass. The claw sign indicates renal parenchyma origin. Tumor venous extension is seen in 5-10%. Calcifications may be present. A cystic variant may mimic benign multilocular cystic neprhoma. Liver or lung metastases are each seen in approximately 10%, and bone metastases (typically lytic) are seen in approximately 5% of cases. Staging of Wilms tumor uses the national Wilms Tumor Study (NWTS) system, which is a combination of radiologic and post-surgical findings: Stage I: Completely resected mass confined to the kidney. Two year survival: 95%. Stage II: Completely resected mass with spread to nearby strucutres (e.g., renal capsule or blood vessels). Two-year survival:90%. Stage III: Incompletely resected mass with spread to nearby structures. Two-year survival: 85%. Stage IV: Hematogenous metastases (e.g., to lung, liver, bone, or brain) or lymphatic metastasis outside of the abdomen or pelvis. Two-year survival: 55%. Stage V (unique to Wilms): Bilateral Wilms at the time of diagnosis (approximately 5-10%). Two-year survival: Variable.

Answer 95

Although far more common in adults, renal cell cancer (RCC) does occur in older children and adolescents. Overall, \<1% of all RCCs occur in children, typically in the setting of von Hippel-Lindau syndrome. Renal medullary carcinoma is an especially aggressive variant of renal cell carcinoma affecting patients with sickle cell trait.

Answer 96

Rhabdoid tumor is a rare, aggressive malignancy that may occur in the brain or kidney. Imaging shows an ill-defined, aggressive renal mass. Renal and CNS lesions may be concurrent.

Answer 97

Clear cell sarcoma is an uncommon renal cancer with propensity to metastasize to bone.

Answer 98

The most common primary malignancies to metastasize to the kidneys in children are neuroblastoma, leukemia, and lymphoma. Leukemia is characteristicaly infiltrative, diffuse, and bilateral. Lymphoma has multiple imaging presentations, including multiple masses or diffuse infiltration.

Answer 99

Mesoblastic nephroma is a benign tumor that appears identical to Wilms by imaging, but occurs in younger children typically =1 year old. Although benign, mesoblastic nephroma is always removed surgically since it cannot be differentiated from Wilms. Like Wilms tumor, mesoblastic nephroma arises from persistent metanephric blastema. Mesoblastic nephroma should not be confused with multilocular cystic nephroma, which is a cystic renal mass with a bimodal age distribution, and is not related to the metanephric blastema.

Answer 100

Nephroblastomatosis is the persistence of metaneprhic blastema. The term nephrogenic rest is used when metanephric blastema persists beyond 36 weeks gestation. On imaging, nephroblastomatosis may appear as a discrete, homogenous, nonenhancing renal mass. Nephroblastomatosis is commonly multifocal, confluent, and bilateral. Nephroblastomatosis is a precursor to Wilms tumor, so frequent screening is performed. Worrisome findings on screening include rapid growth, inhomogeneity, and enhancement.

Answer 101

Angiomyolipoma (AML) is a benign renal tumor with elements of blood vessels (angio), muscle (myo), and fat (lipoma). Multiple AMLs are associated with tuberous sclerosis. Most AMLs feature macroscopic fat, which is visible on CT or MRI. An AML larger than 4 cm has a risk of hemorrhage.

Answer 102

Metanephric blastema is one of the two embryologic tissues that forms the genitourinary system. Metanephric blastema develops into the renal parenchyma, while the ureteric bud forms the collecting system. If metaneprhic blastema persists after embryogenesis, it can lead to: Mesoblastic nephroma, a benign tumor that arises from persistent metanephric blastema. Its appearance mimics Wilms but it occurs in neonates. Nephroblastomatosis, which is benign persistent metanephric blastema manifesting as single, multiple, or confluent homogenous renal masses. Nephroblastomatosis has an increased risk of Wilms tumor. Wilms tumor, an aggressive renal malignancy that is the most common childhood renal neoplasm. It typically occurs in children between the ages of 3 and 5 years old.

Answer 103

Multilocular cystic nephroma does not arise from mesonephric blastema and is not related to mesoblastic nephroma. Multilocular cystic nephroma is a cystic renal mass with a bimodal age distribution, seen in young boys and middle-aged women.

Answer 104

Neuroblastoma is a primitive neural crest cell malignancy that arises from the sympathetic chain, most commonly from the adrenal gland. The mean age at diagnosis is 2 years. A typical CT appearance of an adrenal neuroblastoma is a suprarenal mass, with calcifications seen in ~50%. Neuroblastoma tends to encase vessels, while Wilms tumor is known to displace vessels. On MRI, neuroblastoma often invades into neural foramina and the spinal canal. Diffusion is often restricted, reflecting hypercellularity. Neuroblastoma is positive on I-123 MIBG scintigraphy. Metastases may be found in 75% of patients and commonly involve the bone marrow (typically permeative and lytic). A classic presentation fo metastatic neuroblastoma is an intracranial, subdural mass originating from the marrow. For purposes of neuroblastoma staging, "midline" is defined as the contralateral edge of the vertebral body (i.e. for a left neuroblastoma, "midline" is the right lateral edge of the vertebral body). Stage I: Tumor limited to organ of origin (e.g. adrenal). Two-year survival 75%. Stage II: Local spread (nodes may be positive), but no disease crosing midline. Two-year survival: 75% Stage III: Local spread, crosses midline. Two-year survival: 25% Stage IV: Distant metastases. Two year survival: 25% Stage 4S: Stage I or II with metastases confined to the skin, liver, and bone marrow, and age \<1 year (better prognosis than stage 3 or 4). Stage 4S may also apply to children up to 18 months. Two-year survival: 75%

Answer 105

Ganglioneuroma is a benign neurogenic tumor that appears similar to neuroblastoma on imaging. Ganglioneuroblastoma is intermediate in biological behavior between benign ganglioneuroma and malignant neuroblastoma. In contrast to neuroblastoma, ganglioneuroma affects slightly older children (most common age of a ganglioneuroma patient is 6 years old) and only 50% of ganglioneuromas are positive on I-123 MIBG scintigraphy. MRI classically shows restricted diffusion of a neuroblastoma, but not in ganglioneuroma.

Answer 106

Adrenal hemorrhage is typically diagnosed by ultrasound as a hypoechoic, avascular, suprarenal mass. Hemorrhage may appear similar to neuroblastoma on initial ultrasound, but a follow-up scan would demonstrate involution. Old hemorrhage may calcify.

Answer 107

Adrenal cortical carcinoma is an extremely rare disease, with a prevalence of approximately 1-2 cases per million per year. When occuring in children, it may be associated with Beckwith-Wiedemann and Li-Fraumeni syndromes. Adrenal cortical carcinoma has a bimodal age distribution, seen in children younger than 5 years and adults in their 4th and 5th decades.

Answer 108

The differential diagnosis for cystic pediatric pelvic masses depends on the sex of the child. A pediatric cystic pelvic mass is most likely due to a congenital genitourinary anomaly.

Answer 109

A urachal anomaly results from incomplete obliteration of the embryologic allantois. The urachus is the remnant of the allantois, which connects the urinary bladder to the umbilical cord. There is a risk of adenocarcinoma if a urachal anomaly is not resected. Patent urachus (most common): Connection between bladder and umbilicus (vesico-cutaneous fistula). Urachal cyst: Noncommunicating cyst between the bladder and umbilicus. Urachal sinus: Blind-ending sinus at umbilicus. Vesicourachal diverticulum: Blind-ending bladder diverticulum. A rectal duplication cyst is a rare type of gastrointestinal duplication cyst, usually occurring in the retrorectal space. They are typically resected due to malignant potential.

Answer 110

A dilated fluid or blood-filled vagina and/or uterus may be in response to hormonal stimulation and outflow obstruction, either in the neonatal period (fluid-filled) or at puberty (blood-filled) Hydrometrocolpos: Vagina and uterus dilated with fluid. Hydrocolpos: Vagina dilated with fluid. Hematomerocolpos: Dilated vagina and uterus filled with blood; occurs at menarche with vaginal outflow tract obstruction (e.g., congenital imperforate hymen). Ovarian dermoid cyst, otherwise known as a mature cystic teratoma.

Answer 111

A Mullerian duct cyst is caused by incomplete regression of the Mullerian ducts. In a normal male, the Mullerian ducts regress. A persistant Mullerian duct remnant can cause a Mullerian duct cyst. In a normal female, Mullerian ducts (paramesonephric ducts) develop into the fallopian tubes, uterus, cervix, and upper vagina. The prostatic utricle is a normal midline structure that is the terminal remnant of the Mullerian duct. It arises from the posterior urethra near the verumontanum (ridge of the posterior urethra near the seminal vesicle insertion). When associated with hypospadia (urethra opens along the ventral penile shaft), a protatic utricle can become very large.

Answer 112

Solid pelvic masses are less likely to represent geniourinary anomalies, and are more concerning for neoplasm.

Answer 113

Rhabdomyosarcoma is the most common sarcoma of childhood, occuriring equally commonly in the pelvis and head and neck (together making up almost 80% of cases). Imaging features a characteristic lobulated, bunch of grapes appearance.

Answer 114

Sacrococcygeal tertoma is usually apparent on prenatal imaging. When detected after birth the characteristic clinical appearance is a skin-covered mass extending from the midline buttocks. Sacrococcygeal teratoma has a heterogenous iamging appearance with cystic, solid, and fatty components.

Answer 115

The physis, commonly known as the growth plate, consists of four histological zones of cartilage arranged in layers. The zone closest to the metaphysis is the zone of provisional calcification, composed of chondrocytes that undergo apoptosis after preparing the matrix for calcification. New bone subsequently forms along the scaffolding formed by these chondrocytes, leading to longitudinal growth.

Answer 116

The unfused physis is the weakest part of the developing skeleton. An injury that can cause a ligament sprain in an adult may result in physeal fracture in a child. The Salter Harris (SH) system classifies physeal fracture based on involvement of physis and adjacent epiphysis and metaphysis. In general, the higher the classification, the greater the chance of growth disturbance. Type I: Injury limited to the physis. SH I injuries are often radiographically occult if the epiphysis is not displaced. The physis may be asymmetrically widened. In the absence of physeal widening, the diagnosis of a SH I injury can be suggested based on soft-tissue swelling around the physis. Examples: Slipped capital femoral epiphysis and gymnast's wrist (physeal widening caused by chronic stress on the wrist, which may mimic rickets). Type II: Fracture extends to metaphysis Type III: Fracture extends to epiphysis. Example: Juvenile tillaux fracture, a distal tibial epiphseal fracture. Type IV: Fracture goes through metaphysis, physis, and epiphysis. Example: Triplane fracture, comprised of 3 fractures of the distal tibia: Oblique fracture through the metaphysis, vertical through the epiphysis, and horizontal fracture through the physis. Type V: Physis is crushed. Mnemonic: SALTR (Slip, Above, Lower, Through, Ruined or Rammed)

Answer 117

Six separate ossification centers, each appearing at different stages of development make evaluation of the pediatric elbow challenging. However, the cartilaginous ossification centers always ossify in the same order, which can be remembered with the mnemonic CRITOE: (Capitellum (typically ossifies between 6 months and 1 year of age). Radial head. Internal (medial) epicondyle. Trochlea. Olecranon. External (lateral) epicondyle (typically ossifies between 10 and 14 years of age). An elbow effusion, as evidence by displacement of the anterior and/or posterior fat pads (posterior more sensitive), is pathognomonic of a fracture, even if no fracture is visible. The elbow ligament is evaluated with the anterior humeral and radiocapitellar lines. Anterior humeral line: Drawn along the anterior humeral cortex, the anterior humeral line should pass through the middle of the ossified capitellum on the lateral view. If abnormal, suggests supracondylar fracture. Radiocapitellar line: Drawn through the radial shaft, the radiocapitellar line should pass through the capitellum on all views. If abnormal, suggests elbow dislocation. Supracondylar fracture is the most common pediatric elbow fracture. Lateral condyle fracture is the second most common fracture. In contrast, the most common adult fracture is of the radial head.

Answer 118

Toddler's fracture is a nondisplaced spiral fracture through the tibial metadiaphysis, caused by a rotational force to the leg. Toddler's fracture may be clinically difficult to diagnose. Radiograph shows a hairline spiral lucency through the distal tibia. Nondisplaced fractures of the cuboid and calcaneus may appear similar, with a faint sclerotic band sometimes the only sign of a fracture.

Answer 119

Buckle fractures are uniqe to the pediatric skeleton, representing a buckling of cortex rather than a true break. Buckle fractures can be subtle on imaging and sometimes are only detected by careful inspection of the cortex. Normally, the cortex should be so smooth that a virtual marble can roll down the cortex without bouncing off. Any focal cortical irregularity in a child should raise concern for a buckle fracture.

Answer 120

An apophysis is a growth plate that does not contribute to longitudinal growth. There are five pelvic apophyses and two proximal femoral apophyses, which arise in puberty and fuse by the third decade. The apophyses are the weakest link of the myotendinous unit. Pelvic apophyses close relatively late in skeletal development and are therefore susceptible to avulsion. Apophyseal avulsion fractures occur most commonly in athletic adolescents, who have strong muscles and open apophyses. Acute injuries appear as an avulsed bone fragment. Subacute avulsions are more complex appearing, as the donor site may undergo mixed lytic and sclerotic change in an attempted reparative response. Avulsion injuries may be subtle as they are Salter Harris I equivalent fractures. There is often minimal or no displacement of the otherwise normal-appearing apophyseal ossification. Iliac crest apophysis: Abdominal muscles. Anterior superior iliac spne (ASIS): Sartorius. Anterior inferior iliac spine (AIIS): Rectus femoris. Ischial tuberosity apophysis: Hamstrings. Pubic ramus: Hip adductors and gracilis. Greater trochanter: Gluteus medius and minimus. Lesser trochanter: Iliopsoas. Although a lesser trochanter avulsion may occur in an athletic adolescent due to avulsion of the iliopsoas insertion, in an adult a lesser trochanter fracture is suspicious for a pathologic fracture.

Answer 121

If there is clinical or radiographic concern for child abuse, a complete skeletal survey using high-resolution bone technique (for children under 2 years of age) should be performed, including frontal views of all long bones, rib views with obliques, skull, pelvis, hand/feet, and entire spine. The images are reviewed by the radiologists while the child is still in the department. Bone scintigraphy is more sensitive for posterior rib fractures, but has a higher radiation dose than radiography, is insensitive for skull fractures, and cannot evaluate fracture morphology for age. The age of fractures is estimated by the presence of callus formation. In general, a fracture is less than two weeks old if there is no callus, and at least one week old if there is callus. These estimates are rough guidelines. A younger child will form callus and heal more quickly.

Answer 122

These fractures are highly specific for child abuse, but are not always seen. If any of these fractures are seen, immediate concern must be raised for child abuse. Classic metaphyseal lesion (also called metaphyseal corner fracture or bucket handle fracture) is highly specific for abuse, adn is a circumferential fracture through the peripheral spongiosa bone of the distal metaphysis, most commonly around the knee or ankle. A classic metaphyseal lesion is thought to be due to violent shaking. The classic metaphyseal lesion typically heals quickly (within 10 days) without callus formation, so prompot radiography is essential for diagnosis. Posterior rib fracture is also highly specific for abuse, but may be very difficult to diagnose when acute. A repeat chest radiograph with bone technique can be performed in the acute setting, or follow-up radiograph after one week to view interval callus formation. Unlike in adults, rib fractures are not typically seen after CPR in children. In the rare case of rib fractures from CPR, fractures tend to be anterior and lateral, not posterior. Scapula fracture. Sternum fracture. Spinous process fracture.

Answer 123

These fractures should raise suspicion for child abuse, but are not highly specifc. More than one fracture. Fracture out of proportion to the history. Digital fracture in infants. Long bone fracture in non-ambulatory child. Complex skull fracture.

Answer 124

These fractures are commonly seen, both in the setting of child abuse and accidental trauma, but are not specific for child abuse when seen in isolation. Linear skull fracture. Long bone fracture in ambulatory child.

Answer 125

Bone dysplasias are characterized by impairment of normal growth yielding an abnormal skeleton. The impairment can involve growth slowing down, speeding up, or can cause the bones to grow in an unusual manner. Several terms used to describe abnormal limb growth include: Rhizomelia: Proximal limb shortening (e.g. humerus is too short). Mesomelia: Middle limb shortening (e.g., radius is too short). Acromelia: Distal limb shortening (e.g. hand or wrist is too short). Micromelia: Entire limb is shortened. Amelia: Limb is absent.

Answer 126

Achondroplasia is the msot common cause of dwarfism. Affected individuals have normal intelligence. Key radiographic findings include abnormal morphology of the lumbosacral spine and pelvis: Narrowing of interpedicular distances in the lower spine causes spinal stenosis that is compensated for by characteristic lumbar lordosis as the child learns to walk. Posterior scalloping of the vertebral bodies. Characteristic tombstone iliac wings. Flat acetabula, with short femoral necks. Other findings include frontal bossing of the skull

Answer 127

Thanatophoric is most common lethal skeletal dysplasia. It is inherited in an autosomal dominant manner. Key radiographic findings are focused on the vertebral bodies and femur: Flattening of vertebral bodies (platyspondyly), causing H-shpaed vertebral bodies with diffuse narrowing of interpedicular distance. Curved telephone receiver femurs.

Answer 128

Osteogenesis imperfecta (OI) represents a varied spectrum of disorder due to abnormal type I collagen. OI type II is lethal. Key radiographic findings include multiple fractures in the ribs (causing characteristic accodion ribs), vertebral bodies, and long bones. Additional findings include: Bowed long bones. Osteopenia. Wormian bones in skull, which are secondary to non-coalesced ossification centers in the skull. The differential diagnosis for multiple fractures includes OI, rickets and child abuse. Of these three, OI is the only entity to cause antenatal fractures. With rickets one would not expect antenatal injury. Fractures and osteopenia may be present. With child abuse one would not expect osteopenia or antenatal injury. Fractures may be present.

Answer 129

Asphyxiating thoracic dystrophy is an autosomal recessive disorder of a congenitally small thorax causing respiratory distress. In addition to the small thorax and associated pulmonary dysplasia, bony findings include: Short ribs that are bulbous anteriorly. High-riding handlebar clavicle. Trident acetabulum.

Answer 130

Cleidocranial dysostoses is a skeletal dysplasia characterized primarily by abnormalities in the clavicles. Affected patients are of normal intelligence but tend to be short. The key radiographic finding is complete or partial absence of the clavicles. Cleidocranial dysostosis is strongly associated with wormian bones in the skull. Additional radiographic findings of cleidocranial dysostosis include: Delayed ossification of the skull (neonatal). Widened pubic symphsis (typically not seen until later in life).

Answer 131

Several skeletal dysplasias and metabolic bone diseases can cause stippling of the epiphyses, including: Chondrodysplasia punctata, a short-limbed dwarfism (usually rhizomelic). Multiple epiphyseal dysplasia (Fairbank disease), a mildly short-limbed, autosomal dominant skeletal dysplasia that manifests in late childhoo or adolescence. Hypothyroidism. Complications of maternal warfarin use in a newborn.

Answer 132

The enchondromatosis are characterized by multiple intra-osseous benign cartilaginous tumors in an asymmetric distribution. These syndromes are associated with an increased risk of malignant transformation to chondrosarcoma (Maffuci \> Ollier) Ollier disease is an enchondromatosis without associated abnormalities. Maffuci syndrome is an enchondromatosis with venous malformations, which cause phleboliths that are evident on radiography.

Answer 133

Multiple hereditary exostoses is an autosomal dominant disorder of multiple benign osteochondromas (also called exostoses) growing from the metaphyses of long bones. Complications include pain, deformity, and malignant transformation into low-grade chondrosarcoma (between 5 and 25% of cases). In contrast to enchondromatosis, skeletal involvement is usually symmetric bilaterally.

Answer 134

Mucopolysaccharidoses are a group of lysosomal storage disorders including Hurlers, Morquio, and Hunters. These disorders share common radiographic findings and are typically distinguished clinically and biochemically. Key radiographic findings include anterior vertebral body beaking, thickened ribs, and undertubulated bones. Other findings include: Madelung deformity of the wrists (wedge-shaped proximal carpal row, with radius shifted towards ulna). Thickened calvarium with a J-shaped sella.

Answer 135

Hurlers features anterior beaking of the vertebral bodies, primarily inferiorly.

Answer 136

Morquio also features anterior beaking of middle portion of the vertebral body (mnemonic: Morquio/middle). Morquio is associated with spinal stenosis and atlantoaxial instability.

Answer 137

A limp (abnormal gait pattern caused by pain) should be carefully evaluated and may be secondary to trauma, septic arthritis, chronic fracture, avascular necrosis, or lymphoma.

Answer 138

Infection of the synovium and joint space is an orthopedic emergency as joint destruction and growth arrest may occur without prompt washout and antibiotics. Any hip effusion must be urgently aspirated to evaluate for septic arthritis. The primary differential consideration for septic arthritis is aseptic toxic synovitis, which is a self-limited noninfectious diagnosis of exclusion. Less common causes of hip effusion and limp include hemarthrosis in trauma or hemophilia (history is usually evident). Septic arthritis is usually secondary to hematogenously seeded metaphyseal osteomyelitis that breaks through the periosteum to infect the joint capsule. S. aureus is the most common cause. Plain film findings are not sensitive or reliable for evaluation of effusion, but include: Displacement or distortion of gluteal or psoas fat planes. The gluteus medius and minimus insert on the greater trochanter. The psoas inserts on the lesser trochanter. Widening of the teardrop distance (space between the lateral margin of the pelvic teardrop and the medial margin of the femoral head). The teardrop is the antero-inferior acetabulum. Ultrasound is the imaging modality of choice. Both sides should be compared for symmetry.

Answer 139

Slipped capital femoral epiphysis (SCFE) is a Salter I fracture of the proximal femoral epiphysis (displacement of the epiphysis from the metaphysis) seen in obese preadolescents (most affected children are between 10 and 16 years old). SCFE typically affects children slightly older than those with Legg-Calve-Perthes disease. Initial findings on an AP view can be subtle, including asymmetric widening of the proximal femoral growth plate and lack of intersection of Klein's line with the femoral head. Although Klein's line is drawn on AP view, the physeal widening and displacement is best evaluated on the frog-leg lateral projection. The contralateral hip should always be carefully evaluated. SCFE may be bilateral, but is usually asymmetric.

Answer 140

Legg-Calve-Perthes (LCP) disease is avascular necrosis of the capital femoral epiphysis ossification center. LCP is of unknown etiology and typically occurs in children betwen the ages of 4 and 8 years. LCP is usually unilateral. A systemic cause should be sought when bilateral, such as sickle cell disease or steroids. Imaging findings are dependent on stage and chronicity. Early LCP can be subtle, and often show multiple modalities are used for initial diagnosis. Early LCP may show subtle sclerosis of the femoral head on radiography. There is typically decreased uptake on bone scan. Late LCP shows secondary signs of osteonecrosis. The femoral head becomes flattened and distorted, with secondary changes of osteoarthritis. Bone scan of late LCP typically shows increased uptake due to attempted repair.

Answer 141

Osteosarcoma is teh most common primary pediatric bone tumor. There are over 10 types of osteosarcoma, with the most common subtype the conventional (intramedullary) type, representing 75% of all osteosarcomas. Conventional osteosarcoma is seen most commonly about the knee in the distal femur or proximal tibia. The characteristic radiographic appearance of conventional osteosarcoma is a destructive lesion often invading the cortex, with extensive osteoid matrix.

Answer 142

Ewing sarcoma is the second most common primary pediatric bone tumor. It is an aggressive, small round blue cell tumor of neuroectodermal differentiation. Ewing sarcoma most commonly arises from the femoral diaphysis, followed by the flat bones of the pelvis. Ewing may also develop in the tibia, humerus, adn ribs. The lung is the most common site of metastasis. The characteristic radiographic appearance is a permeative lesion in the medullary cavity with wide zone of transition and associated aggressive lamellated (onion-skinning) or spiculated periosteal reaction. Ewing often causes a soft-tissue mass, which can be difficult to see by radiography due to lack of ossification.

Answer 143

Langerhans cell histiocytosis (LCH) is abnormal proliferation of Langerhans cells with a variety of clinical manifestations, ranging from an isolated lytic bony lesion to fulminant systemic disease. Langerhans cells are dendritic cells (histiocystes) that normally live in the epidermis and lymph nodes, where they act as antigen-presenting cells. Histopathologically, Birbeck bodies are seen on electron microscopy within the histiocytes. Clinical subtypes of LCH have varied presentations. Eosinophilic granuloma (osseous LCH) features skeletal involvement only. It may be mono- or polyostotic. Despite the name, the involvement of eosinophils is variable. Hand-Schuller-Christian (multifocal, unisystem) is a clinical triad of pituitary hypophysitis (causing diabetes insipidus), exopthalmos, and lytic bone lesions (typically affecting the skull). Lettere-Siwe (multifocal, multisystem) is a fulminant disease with multisystem involvement, primarily seen in young infants and toddlers under age 2. Prognosis is poor. Pulmonary LCH (PLCH) is a disease of adult smokers, discussed in the thoracic section. Osseous LCH is occasionally seen in conjunction with PLCH. In clinical practice, the most important factor is thought to be determination of unifocal or multifocal disease rather than classification. The eosinophilic granuloma variant of LCH is relatively common and may present clinically with pain, tenderness, and fever, often mimicking osteomyelitis. Children between ages 5 and 15 are typically affected. The appearance of the affected bone depends on the bone involved: Skull: Beveled edge lytic lesion. Flat bones (e.g., pelvis): Hole within a hole lytic lesion. Long bone (diaphysis most common, but may occur anywhere including rarely the epiphysis): Permeative destruction, with later lytic lesion and faint rim of sclerosis. Spine: Complete vertebral body collapse (vertebra plana). Maxilla: floating teeth. Along with infection, eosinophilic granuloma should be considered in the differential diagnosis in any patient under 30 with a lytic lesion anywhere.

Answer 144

The initial findings of osteomyelitis are often subtle on radiography and may require a combination of plain radiographs, MRI, and scintigraphy for accurate early diagnosis. Osteomyelitis in children is most commonly hematogenous, with the metaphyseal marrow the most common site of initial seeding In infants, the epiphysis receives blood supply from transphyseal vessels arising from metaphysis, so infection can cross the physis. In older children, capillaries do not cross the physis, so transphyseal extension of a metaphyseal infection is uncommon. The most common organism implicated in hematogenous osteomyelitis is S. aureus, with Salmonella seen in sickle cell patients. The imaging findings on radiography, MRI, and scintigraphy follow the anatomic progression of infection. The initial hematogenous infection is intramedullary and then subsequently spreads through the cortex and uplifts the periosteum. The pediatric periosteum is only loosely adherent to bone, and the purulent infection is able to dramatically uplift the periosteum, causing a prominent periosteal reaction. It usually takes 10-15 days for findings to become evident on radiography. The initial finding may be focal osteopenia due to hyperemia. Subsequently, a lucent, often agressive-appearing medullary lesion can erode throught the cortex and cause periosteal reaction. MRI and scintigraphy are much more sensitive for the detection of early osteomyelitis.

Answer 145

Isolated discitis is unique to children, due to the presence of blood vessels directly feeding the intervertebral disk. In adults, infection can spread through the disk, but in children infection begins in the disk. A typical clinical history of discitis in a young child up to 4 years old with preceding upper respiratory tract infection and back pain or refusal to sit. Discitis most commonly occurs in the lumbar spine in young children. Less commonly, discitis may occur in pre-teen children in the thoracic spine. The initial radiographic findings are disk space narrowing and vertebral end plate irregularity. These findings may be subtle. Plain films may also be normal. Because persistant back pain is never normal in children, further evaluation with MRI is recommended if cliical suspicion for discitis is high. MRI shows narrowing of the disk space, with bone marrow edema of two adjacent vertebral bodies. The affected vertebral bodies may enchance, and enhancement and edema may extend into the soft tissues and epidural space.

Answer 146

Chronic recurrent multifocal osteomyelitis (CRMO) is a nonpyogenic, inflammatory disorder that can mimic osteomyelitis. It tends to occur in lower extremity long bones. CRMO is typically a self-limited diagnosis. Biopsy may need to be performed to exclude pyogenic infection. The key imaging finding is migratroy lytic and sclerotic lesions in time and space. CRMO may be indistinguishable from pyogenic osteomyelitis on radiographs and MRI. Unlike infectious osteomyelitis, CRMO does not feature soft tissue abscess, bony sequestra, or fistula. CRMO is associated with SAPHO syndrome (Synovitis, Acne, Pustulosis, Hyperostosis, Osteitis).

Answer 147

Leukemia is the most common pediatric malignancy, with bony changes seen in \>50% of patients. Imaging findings can be varied. One of the most distinctive radiographic features of the leukemia is the metaphyseal lucent band. The etiology of the lucent bands is controversial, thought to be possibly due to malnutrition or vitamin deficiency in young children. The differential diagnosis of metaphyseal lucent bands includes: Leukemia, lymphoma, severe illness, TORCH infections, scurvy. Other osseous findings of leukemia include generalized osteopenia or permeative lytic lesions.

Answer 148

Rickets is a metabolic bone disorder caused by inadequate vitamin D or abnormal vitamin D metabolism. It is characterized by abnormal calcification at the zone of provisional calcification, leading to abnormal physeal development. Radiographs show expansion, fraying, and cupping of the long bone metaphyses, often associated with adjacent metaphyseal new bone. Other findings of rickets include bowing of the legs, osteopenia, and fractures. The classic rachitic rosary represents anterior cupping of the ribs with widening of the rib epiphyseal cartilage. The skull may become demineralized. Oncogenic rickets is a variant of rickets seen with hemangiopericytoma or nonossifying fibroma due to tumor metabolites that cause deranged vitamin D metabolism.

Answer 149

Syphilis is caused by the spirochete Treponema pallidum. Syphilis can be transmitted in utero through the placenta to cause congenital syphilitic osteomyelitis. The Wimberger sign is destructive erosion of the medial aspect of the proximal tibial metaphysis. The Wimberger sign is not to be confused with the Wimberger ring sign of scurvy, which is increased density of the ossification centers. Syphilis is one of many causes of symmetric periosteal reaction in a child.

Answer 150

Juvenile idiopathic arthritis (JIA), also known as juvenile rheumatoid arhtritis (JRA) and juvenile chronic arthritis (JCA), is the most common chronic arthropathy of childhood. It is a systemic idiopathic disease defined as being present for more than 6 weeks in a patient younger than 16 years old. JIA is usually rheumatoid-factor negative. The most common subtype of JIA is pauciarticular disease, typicaly affecting young girls. Regardless of subtype, the knee is the most commonly affect joint, but any joint can be affected. The imaging appearance reflects the underlying pathophysiology of synovitis, as the earliest radiographic changes are joint effusion, soft tissue swelling, and osteopenia. Later changes include periostitis and erosions. Chronic disease leads to eventual joint ankylosis, which is in contrast to adult rheumatoid arthritis, where ankylosis is rare. The most common sites of ankylosis are in the wrist, at the carpometacarpal joints, adn the cervical spine. Cervical spine ankylosis in a child may appear similar to Klippel-Feil syndrome. In contrast to Klippel-Feil, JIA does not feature segmentation anomalies. Accelerated skeletal maturation and accelerated bone growth are caused by synovitis and hyperemia, which lead to premature fusion of the physes and/or abnormal bone growth. Still disease is an acute systemic subtype of JIA affecting children under the age of five. Still disease presents with fever, anemia, leukocytosis, hepatosplenomegaly, and polyarthritis. Boys and girls are affected equally in Still disease.

Answer 151

Developmental dysplasia of the hip (DDH) is abnormal development of the femoral head-acetabular relationship. An abnormally shallow acetabular angle results in uncovering of the femoral head by the acetabulum. There is an increased incidence of DDH in breech births, so all breech births are typically screened by ultrasound. Ultrasound is performed a few weeks after birth. Imaging is delayed because of the effects of perinatal maternal hormones on neonatal ligamentous laxity. The alpha angle is the angle formed by the bony ilium and acetabular roof, obtained from the coronal hip ultrasound. A normal alpha angle is greater than 60 degrees. The bony portion of the acetabular roof should cover at least 50% of the cartilagineous femoral head. An alpha angle less than 60 degrees or less than 50% coverage of the femoral head by acetabulum is abnormal, suggesting DDH After femoral head ossification (typically after 6 months of age) radiographs are performed. On pelvic radiography, the ossified femoral head should normally sit in the inner lower quadrant formed by the intersection of the Hilgenreiner and Perkins lines.

Answer 152

The osteochondroses are a heterogenous group of disorders that were at one point thought to be initiated by avascular necrosis. The current understanding is that most of these disorders are secondary to trauma. While many are associated with avascular necrosis, AVN is not thought to be the initiating factor. Most are common in males.

Answer 153

Blount disease is an osteochondrosis of the proximal tibial metaphysis, causing tibial varus (bowing) and internal rotation, which eventually leads to progressive deformity, gait deviations, and leg-length discrepancy. The infantile form of Blount disease is thought to be due to early walking and obesity and is typically bilateral. The adolescent form is seen in children over 6 years old and is usually unilateral.

Answer 154

Madelung deformity is medial sloping of the distal radius caused by dysplasia of the medial distal radial physis and resultant growth disturbance.

Answer 155

Panner disease is osteochondrosis of the capitellum.

Answer 156

Little league elbow is osteochondrosis of the capitellum.

Answer 157

Scheurmann kyphosis is a syndrome of avascular necrosis of multiple thoracic vertebral bodies leading to multiple compression fractures.

Answer 158

Legg-Calve-Perthes disease is osteochondrosis of the capital femoral epiphysis.

Answer 159

Kienbock disease is osteochondrosis of the carpal lunate

Answer 160

Osgood-Schlatter disase is osteochondrosis of the tibial tuberosity.

Answer 161

Freiberg infraction is osteochondrosis of the second metatarsal head.

Answer 162

Kohler disease is a self-limited osteochondrosis of the navicular bone.

Answer 163

Sever disease is calcaneal apophysitis (rather than an osteochondrosis) and is a cause of heel pain. Sclerosis of the calcaneal apophysis is nonspecific and can be seen in asymptomatic children, although greater fragmentation of the apophysis may be associated with pain.

Answer 164

Torticollis is caused by fibromatosis coli (idiopathic sternocleidomastoid enlargement) resulting in an inability to fully straigten the neck. It usually resolves with physical therapy.

Answer 165

Tarsal coalition is abnormal joining of two normally separate bones in the tarsus. The three types of coalition are fibrous, cartilaginous, and osseous. The two most common coalitions (together making up 90% of all tarsal coalitions) are talocalcaneal and calcaneonavicular. Tarsal colatition clinically presents as foot pain in the child as the coalition begins to ossify.

Answer 166

Carpal coalition is abnormal joining of carpal bones. Carpal coalition is usually asymptomatic but may be a cause of wrist pain. Like tarsal coalition, the coalition may be fibrous, cartilaginous, or osseous. Lunotriquetral coalition is the most common carpal coalition. Capitohamate is second most common carpal coalition.

Answer 167

The periosteum is a thin membrane covering the entire surface of the bone excluding those areas covered by cartilage. It contributes to bone production and remodeling. Irritation of the periosteum, which can be due to trauma, infection, inflammation, neoplasm, or metabolic disturbance, can cause periosteal reaction. The terms "periosteal reaction," "periostitis", and "periosteal new bone formation" are commonly used as synonyms. Periosteal reaction is simply a nonspecific response to injury resulting in periosteal new bone production. Periosteal reaction may also be associated with tumors or infection, typically producing an aggressive appearance in these disorders. The morphology of aggressive periosteal reaction is discussed in the musculoskeltal imaging section.

Answer 168

Physiologic periosteal reacion occurs in infants 1-4 months old, thought to be due to rapid bone growth and loosely adherent periosteum. The periosteal reaction is smooth and thin, and usually only involves the lateral or medial aspect of the long bones.

Answer 169

Neonates on prostaglandin therapy for congenital heart disease (to maintain ductal patency) may have periosteal reaction. Prostaglandins are thought to decrease osteoclast bone resorption.

Answer 170

Subperiosteal spread of pyogenic infection elevates the periosteum and irritates it, usually casuing an aggressive periosteal reaction. Congenital syphilis causes periosteal reaction.

Answer 171

Multiple malignancies, including leukemia, neuroblastoma, Ewing sarcoma, and osteosarcoma can produce an aggressive periosteal reaction.

Answer 172

Healing fractures (both accidental trauma and child abuse) may cause periosteal reaction.

Answer 173

Rickets, scurvy (which is also characterized by epiphyseal sclerosis - the Wimberger rim sign), and hypervitaminosis A may all cause periosteal reaction.

Answer 174

Multiple syndromes may cause periostitis. Caffey disease (infantile cortical hyperostosis) is a rare inflammatory disease causing periostitis of the mandible, scapula, and clavicle.

Answer 175

A full-term newborn will have myelination in several structures at birth, including: Posterior limb of internal capsule, middle cerebellar peduncle, ventrolateral thalami, dorsal brainstem, and the perirolandic regions. Myelination is most apparent of T1-weighted images. On T1-weighted images myelin is bright; on T2-weighted images myelin is dark. Myelination generally assumes a mature pattern by age 2 years, although the frontal lobes continue to myelinate through adolescence.

Answer 176

Primitive brain forms around the primordial ventricular system, which is lined by pluripotent stem cells called germinal matrix cells. Development of normal cortex is dependent on both germinal matrix cell migration and subsequent organization into the normal six-layered lamination of the cortex.

Answer 177

Polymicrogyria is a malformation of cortical development characterized by a derangement of the normal six-layered organization of the cortex, which leads to abnormally shallow and abnormally numerous sulcation. Polymicrogyria is thought to be caused by disturbance either late in neuronal migration or early in cortical lamellar organization. Polymicrogyria may be caused by in-utero infection (especially CMV), in-utero ischemia, or genetic causes. Clinical manifestations include developmental delay, quadriparesis, or intractable seizures. On MR imaging, sulci appear thick, bumpy, small and irregular. The junction of the polymicrogyric cortex and the white matter is irregular and less well defined than normal. Bilateral perisylvian polymicrogyria is the most common distribution.

Answer 178

Lissencephaly is characterized by absent or decreased cortical convolutions causing a smooth, thickened cortical surface. Instead of the normal six-layered cortex, the cortex is arranged into four primitive layers. Lissencephaly is thought to be due to an arrested band of neurons, which have not completed outward migration to the superficial cortex. Lissencephaly may be caused by CMV, in which case calcifications are often present. Clinically, patients with lissencephaly almost univerally have seizures. Lissencephaly can be subdivided into type I (classical) and type II (cobblestone). The two forms are genetically and embryologically distinct. Cobblestone lissencephaly is associated with cerebellar and ocular malformations and muscular dystrophy (Walker-Warburg syndrome).

Answer 179

Gray matter heterotopia is a range of disorders characterized by clusters of normal neurons in abnormal locations. Gray matter heterotopia may be a cause of seizures. Three main subtypes include periventricular nodular heterotopia, subcortical heterotopia, and marginal glioneural heterotopia.

Answer 180

Agenesis of the corpus callosum is a relativelycommon congenital abnormality. The most common clinical manifestations of agenesis of the corpus callosum are refractile seizures and/or developmental delay. Complete agenesis of the corpus callosum causes secondary abnormalities in ventricular morphology. Colpocephaly (dilation of the occipital horns of the lateral ventricles) may result from decreased white matter volume posteriorly. The lateral ventricles are often parallel in orientation and widely spaced. Medial impressions on the lateral ventricles are caused by Probst bundles, which are axons that normally consititute the corpus callosum but instead pursue an aberrant course parallel to the interhemispheric fissure. The third ventricle may be enlarged and high-riding. The corpus callosum develops from genu (anterior) to splenium (posterior). Various degrees of corpus callosal hypogenesis may occur, the most common being absence of the splenium. Congenital corpus callosal anomalies are often associated with other midline abnormalities including a midline lipoma or interhemispheric cyst.

Answer 181

Schizencephaly is a malformation characterized by a full-thickness cleft of the cerebral hemisphere lined by dysplastic gray matter (usually frompolymicrogyria), forming an abnormal communication between the ventricles and the extra-axial subarachnoid space. Schizencephaly is associated with cortical malformations (gray matter heterotopia), with up to 30% of patients with schizencephaly also having cortical malformations. Schizencephaly has been morphologically classified into open-lip (walls of the cleft are entirely divided by CSF) and closed-lip (walls of the cleft are apposed or incompletely divided). Schizencephaly is associated with septo-optic dysplasia, which is characterized by agenesis of the septum pellucidum and optic nerve hypoplasia. The characteristic imaging finding of schizencephaly is a CSF-filled cortical cleft lined by gray matter. Frontal involvement is most common. There are several other entities that can cause an interruption or cleft in the cortex, but only a schizencephalic cleft is lined by gray matter. Other cortical clefts include: Porencephaly, where there is replacement of cortex by a cystic structure. Encephalomalacia. Surgical resection cavity.

Answer 182

Holoprosencephaly is a complex congenital malformation where the forebrain does not divide into two hemispheres. Holoprosencephaly is associated with midline maxillofacial anomalies including a single central incisor. It is commonly said that "the brain predicts the face". Holoprosencephaly is associated with an azygos configuration of anterior cerebral artery (single ACA). The three subtypes (from most severe to least severe) are alobar, semilobar, and lobar. Alobar holoprosencephaly is the most severe form, characterized by complete lack of separation of the cerebral hemispheres. A single large monoventricle almost always communicates with a large dorsal cyst. Semilobar holoprosencephaly features at least some degree of separation of the posterior cerebral hemispheres. Similar to alobar holoprosencephaly, the anterior hemispheres also fail to separate. Lobar holoprosencephaly is the mildest form, where only the most rostral aspects of the frontal neocortex are not separated. The corpus callosum is absent in the affected region anteriorly, but the posterior corpus callosum (splenium and posterior body) is present.

Answer 183

Chiari I is inferior displacement of the cerebellar tonsils beyond the foramen magnum. The clinical manifestation of Chiari I is variable adn ranges from occasional exertional headaches in an otherwise normal individual to severe myelopathy and brainstem compromise. In babies, Chiari I may be associated with sleep apnea adn feeding problems. The most common complications of Chiari I are cervical syringomyelia and less commonly hydrocephalus. Syringomyelia, also called syringohydromyelia or syrinx, is fluid within the spinal cord. Syringomyelia most commonly represents dilation of the central canal of the spinal cord, which normally extends from the obex of the fourth ventricle to the filum terminale. The syringomyelia associated with Chiari I is fusiform dilation of the central canal that does not typically communicate with the fourth ventricle. Other forms of syringomyelia (typically associated with hydrocephalus) may communicate with the fourth ventricle via the central canal. Both clinical diagnosis and diagnostic imaging criteria for Chiari I are controversial. Inferior protrusion of the cerebellar tonsils is a relatively common finding in asymptomatic individuals. Additionally, the clinical symptoms of Chiari I are nonspecific and include headache and malaise. which may not always be attributable to the inferior protrusion of the tonsils. The classic criterion for diagnosis is herniation of either cerebellar tonsil by 5 mm, or herniation of both tonsils by 3 mm; however, associated findings allowing a more confident diagnosis include pointing of the cerebellar tonsils, crowding of the posterior fossa, and a complication such as cervical spine syringomyelia or hydrocephalus. If the only finding is isolated inferior displacement of the tonsils, the term "borderline tonsillar ectopia" is generally preferred.

Answer 184

Chiari II is a completely different disease from Chiari I; however, a common feature among all Chiari malformations is inferior displacement of the hindbrain. The primary abnormality in Chiari II is herniation of the vermis, cerebellar tonsils, and medulla into the foramen magnum, with resultant beaking of the tectum. A myelomeningocele is universally present, typically lumbar. The fourth ventricle becomes elongated and inferiorly displaced. Approximately 80-90% of children with Chiari II have hydrocephalus necessitating shunt placement, due to fourth ventricular obstruction. Associated supratentorial anomalies include corpus callosal dysgenesis, heterotopias, and sulcation abnormalities.

Answer 185

The Dandy Walker complex features an enlarged posterior fossa, usually associated with a large posterior fossa cyst. Dandy Walker variants are a continuum of disorders of varying severities. An in-utero insult to the developing fourth ventricle is thought to result in fourth ventricular outflow obstruction, cyst-like dilation of the fourth ventricle (which communicates with a retrocerebellar cyst), and resultant inferior vermain hypoplasia. Most patients have hydrocephalus. Upwards displacement of the tentorium by the enlarged fourth ventricle and posterior fossa cyst causes torcular-lambdoid inversion. The torcular herophili is the confluence of the transverse and the straight sinuses, which is pushed superiorly, above the lamboid suture.

Answer 186

Neurofibromatosis type 1 (NF1), also known as von Recklinghausen disease, is a multisystemic neurocutaneous disorder with prominent skin manifestations (e.g., cafe au lait spots), peripheral nerve sheat tumors (e.g., plexiform neurofibroma), CNS malignancies (e.g., optic nerve glioma), and bony abnormalities (e.g., sphenoid wing dysplasia). NF1 is autosomal dominant in 50% of cases and occurs sporadically in 50%, caused by a defect in chromosome 17. In children, "bright spots" or "unidentified bright objects" are almost universally seen on T2-weighted images, thought to be caused by myelin vacuolization. These bright spots are seen most commonly in children ages 4-12 and become less prominent in adults. Neurofibromas are WHO grade I nerve sheath tumors. The cutaneous and subcutaneous nerves are more commonly involved thant he more proximal peripheral nerves. A plexiform subtype is more aggressive and consists of a network of fusiform-shaped masses, with malignant degeneration reported in approximately 5%. Like schwannomas, neurofibromas are likely of Schwann cell origin. The target sign can be seen with either neurofibromas or schwannomas, and reflects central T2 hypointensity thought to be due to a fibrocollagenous core. The target sign is suggestive of benignity. In contrast to schwannomas, neurofibromas are not encapsulated and involve the entire cross-sectional area of the nerve. If a neurofibroma is resected, the parent nerve must therefore be sacrificed. NF1 is associated with multiple brain neoplasms: Optic nerve glioma (50% of these tumors are associated with NF1). Juvenile pilocytic astrocytoma. Brainstem glioma. Bone manifestations of NF1 include: Sphenoid wing dysplasia, which may produce pulsatile enophthalmos or exopthalmos. Posterior vertebral body scalloping. Rib notching (twisted ribbon ribs) due to erosion from neurofibromas of the intercostal nerves. Focal gigantism. Cervical kyphoscoliosis, with a characteristic acute angle. Neural foraminal enlargement, either due to bony dysplasia or a neurofibroma. Tibial bowing. Eye manifestations of NF1 include hamartomas of the iris, known as Lisch nodules. NF1 is also associated with multiple extra-cranial neoplasms: Wilms tumor. Rhabdomyosarcoma. Angiomyolipoma (renal). Leiomyosarcoma.

Answer 187

Neurofibromatosis type 2 (NF2) is an autosomal dominant neurocutaneous disorder completely unrelated to NF1. Despite the name, neurofibromas are not a component of NF2. NF2 is caused by a defect on chromosome 22 and is approximately ten times less common than NF1. NF2 is characterized by the MISME mnemonic: Multiple Inherited Schwannomas, Meningiomas, and Ependymomas. The typical clinical presentation of NF2 is hearing loss caused by bilateral vestibular schwannomas. The presence of bilateral vestibular scwannomas is diagnostic of NF2.

Answer 188

Sturge Weber is a neurocutaneous disorder characterized by facial port-wine stain (capillary malformation), ocular abnormalities, and failure of normal cortical venous development. The port-wine stain typically involves the forehead and upper eyelid, corresponding to the region innervated by the opthalmic branch of the trigeminal nerve (V1). Sturge Weber is a vascular disorder, thought to be caused by failure of regression of the primitive embyrologic cephalic venous plexus. This developmental anomaly results in the formation of leptomeningeal venous angiomatosis, which is a vascular malformation characterized by dilated capillaries and venules. The underlying vascular anomaly ultimately leads to chronic ischemia, cortical atrophy, and cortical calcification. Clinically, patients may have some degree of developmental delay and seizures; however, up to 50% of patients may have normal intelligence. Seizures and developmental delay tend to occur together. Characteristic imaging findings are cortical atrophy and subcortical parenchymal calcifications, which are best seen on CT. Contrast-enhanced MRI demonstrates pial enhancement in regions affected by the leptomeningeal venous angiomatosis. The choroid plexi are typically enlarged from compensatory hypertrophy thought to be related to increased flow.

Answer 189

Tuberous sclerosis is a hamartomatouts disorder affected several organ systems, with multiple skin manifestations. The classical clinical triad of adenoma sebaceum (nodular rash originating in the nasolabial folds), seizures, and mental retardation is not always present. Clinically, most patients have epilepsy, neurocognitive dysfunction, and pervasive developmental disorders. Neuroimaging features multiple T2 hyperintense white matter cortical or subcortical tubers (hamartomas) and subependymal nodules. 15% of patients develop subependymal giant cell astrocytoma (SEGA), which may appear on imaging as a newly enhancing or enlarging subependymal nodule. Extracranial manifestations include: Renal: Multiple angiomyolipomas. Cardiac: Rhabdomyoma. Lung: Lymphangioleiomyomatosis.

Answer 190

A "molar tooth" configuration of the midbrain can be seen in several diseases, including Joubert syndrome and related disorders (JSRD). JSRD clinically present as a hypotonic child with developmental dealy and ataxia. These disorders are often associated with ocular anomalies. The primary abnormality of Joubert syndrome is thought to be aplasia or hypoplasia of the cerebellar vermis. Dysplastic cerebellar tissue is often present. Unlike Dandy Walker complex, hydrocephalus and a large posterior fossa cyst are uncommon.