Pediatric Imaging Flashcards
Normal lateral neck radiograph
Pediatric upper airway obstruction
Upper airway obstruction above the level of the trachea can be congenital (choanal atresia), neoplastic (rhabdomyosarcoma), or infectious (peritonsillar abscess).
Upper airway obstruction can also be classified by anatomic level: Nasal and nasopharygeal (choanal atresia, rhabdomyosarcoma, adenoidal hypertrophy), or oropharyngeal (peritonsillar abscess, thyroglossal duct cyst).
Choanal atresia
Choanal atresia is congenital occlusion of the choanae in the posterior nasal cavity.
Choanal atresia can be osseous, membranous, or mixed. There is almost always some degree of osseous abnormality, with approximately 70% of cases mixed and 30% of cases being a pure bony atresia.
Choanal atresia is often associated with other congenital malformations, most commonly CHARGE syndrome.
Coloboma (gap in iris or retina).
Heart defects.
Atresia of choanae.
Retardation of development.
Genitourinary anomalies.
Ear anomalies.
Juvenile nasopharyngeal angiofibroma (JAA)
Juvenile nasopharyngeal angiofibroma is a highly vascular, benign hamartomatous lesion seen in adolescent males. It typically originates at the sphenopalatine foramen and spreads into the nasopharynx and pterygopalatine fossa, causing bony remodeling along the way. The primary differential is nasal rhabdomyosarcoma, which causes bony destruction.
Nasal rhabdomyosarcoma
Nasal rhabdomyosarcoma is the most common childhood soft-tissue sarcoma, with the head and neck a common primary site. It presents as a highly aggressive mass.
Epiglottitis
Epiglottitis is infectious inflammation of the epiglottis. A very rare disease in the era of Heamophilus influenza immunization, epiglottitis is a true emergency as the airway can obstruct without warning. Modern cases tend to be seen in immunosusceptible individuals, such as HIV patietns or transplant recipients.
The classic radiographic findings of epiglottitis are thickening of the epiglottis seen on the lateral view (the thumbprint sign) in conjunction with thickening of the aryepiglottic folds.
Croup (laryngotracheobronchitis)
Croup is a viral (usually parainfluenza) infection with characteristic inspiratory stridor and barking cough. It affects infants and toddlers. Croup is a clinical diagnosis. The purpose of radiography is to evaluate for other causes of stridor.
The steeple sign is seen on the frontal view and represents loss of the normal shouldering of the subglottic trachea. There may be “ballooning” of the hypopharynx on the lateral view.
Aspirated foreign body
Radiography can’t directly visualize a radiolucent foreign body, although secondary signs of air trapping can suggest the diagnosis.
Decubitus radiographs can be performed to look for non-physiologic persistent expansion of the dependent lung, signifying an obstruction on the persistently expanded side.
Retropharyngeal abscess
Retropharyngeal abscess is purulent infection of the retropharyngeal space and is one of the more common causes of nontraumatic prevertebral soft tissue swelling in children.
Retropharyngeal pseudothickening can be seen if a radiograph is obtained in neck flexion.
A retropharyngeal abscess rarely presents with air in the retropharyngeal tissues unless a foreing body has perforated the esophagus.
CT is usually necessary to determine the nature of radiographic retropharyngeal swelling. In addition to retropharyngeal abscess, the differential of nontraumatic prevertebral swelling includes retropharyngeal cellulitis, lymphoma, and foregut duplication cyst.
Retropharyngeal cellulits appears similar to pharyngeal abscess on radiography, but no drainable fluid collection is seen on CT.
Exudative (bacterial) tracheitis
Exudative tracheitis may clinically present similarly to epiglottitis with fever, stridor, and respiratory distress, and is also potentially life-threatening.
In contrast to croup, exudative tracheitis tends to affect older children and is bacterial in etiology (most commonly S. aureus).
On imaging, intraluminal mebranes may be visible in the subglottic and cervical trachea.
Subglottic hemangioma
A subglottic hemangioma is a benign vascular neoplasm that produces stridor in infancy. It is the most common pediatric subglottic tracheal mass.
Subglottic hemangioma is often associated with cutaneous hemangiomata.
The classic radiographic finding is asymmetric narrowing of the subglottic trachea on the frontal view, although a hemangioma may also cause symmetric narrowing.
Laryngeal papillomatosis
Laryngeal papillomatosis is a cuase of multiple laryngeal nodules due to HPV infection, resulting in thick and nodular vocal cords. Papillomatosis increases the risk of laryngeal squamous cell carcinoma (analogous to cervical cancer risk from HPV).
Papillomas may rarely seed the lungs, causing multiple cavitary nodules.
Tracheal stenosis
Iatrogenic tracheal stenosis (e.g., due to prolonged intubation) may be a cause of stridor.
Congenital tracheal stenosis is usually associated with vascular anomalies.
Tracheobronchomalacia
Tracheobronchomalacia cuases excessive expiratory airway collapse from weakness of the tracheobronchial cartilage. Tracheobronchomalacia may be either congenital or acquired secondary to intubation, infection, or chronic inflammation.
A standard inspiratory CT may be normal. Either expiratory CT or dynamic airway fluorscopy is necessary to diagnose tracheobronchomalacia.
Greater than 50% reduction in cross-sectional area of the airway lumen is suggestive of tracheomalacia, although normal patients may achieve this threshold with a forceful expiration.
Vascular rings and slings
Rings and slings are important vascular causes of stridor in infancy and childhood. The typical initial evaluation is with barium esophagram, followed by CT or MRI if abnormal.
Complete encircling of the trachea and esophagus by the aortic arch or great vessels is a vascular ring.
A vascular sling refers to an anomalous course of the left pulmonary artery, which arises aberrantly from the right pulmonary artery adn traps the trachea in a “sling” on three sides.
An important clue to a potential vascular cause of stridor is a right sided aortic arch visualized on the frontal radiograph. The pulmonary artery sling is the only vascular anomaly that causes stridor in a patient with a normal (left) aortic arch.
The three most important vascular causes of stridor are double aortic arch, right arch with aberrant left subclavian artery, and pulmonary sling. Each of these will show abnormality on the lateral radiograph or esophagram.
The double aortic arch and right arch with aberrant left subclavian artery look the same on radiography/esophagram, each producing a posterior impression on the esophagus.
Double aortic arch
Double aortic arch is the most common vascular ring. The arches encircle both the trachea and esophagus, adn may cause stridor.
The right arch is usually superior and larger in caliber than the left.
For presurgical planning, the goal of the radiologist is to determine which arch is dominant, typically with MR; the surgeon will then ligate the non-dominant arch to alleviate the stridor.
Right arch with aberrant left subclavian artery
The second most common vascular ring is a right aortic arch with an aberrant left subclavian artery. The right arch indents the anterior trachea while the aberrant left subclavian artery wraps posteriorly around the esophagus. The ring is completed by the ligamentum arteriosum.
In contrast, the mosre common anatomical variant of a left arch with an aberrant right subclavian artery is a (usually) asymptomatic normal variant that is not a vascular ring.
On the frontal view, a right arch with aberrant left subclavian artery produces a leftward impression/deviation of the tracea by the right aortic arch.
Pulmonary sling: Anomalous origin of the left pulmonary artery from the right pulmonary artery
An anomalous left pulmonary artery, arising form the right pulmonary artery, forms a sling by coursing in between the trachea and esophagus. Usually only the trachea is trapped in the sling, but occasionally the bronchus intermedius may also be compressed.
Pulmonary artery sling is the only vascular cause of stridor in a patient with a left arch. The aortic branching pattern is normal.
Pulmonary artery sling is associated wtih tracheal anomalies including tracheomalacia and bronchus suis (RUL bronchus originating from trachea).
Left aortic arch with aberrant right subclavian artery
A left aortic arch with an aberrant right subclavian artery is not a ring or a sling, and is not a cause of stridor. It almost never causes symptoms, but in the rare case that is does, dysphagia may result, which is called dysphagia lusoria.
Innominate artery syndrome
In infants, the large thymus can occasionally cause the normal innominate artery to press against the anterior trachea, potentially producing innominate artery syndrome.
Innominate artery syndrome is not a vascular ring, and it is controversial whether this entitiy is a clinically relevant form of breathing difficulty.
Medical respiratory distress in the newborn
Multiple processes can cause respiratory distress in a neonate, including pulmonary disease, congenital heart disease, thoracic mass, airway disorders, skeletal abnormalities, vascular anomalies, etc.
Despite this broad range, there are four classic differentials for a newborn with “medical respiratory distress” - that is, a baby that appears to be anatomically normal by radiograph (i.e., without cardiomegaly or thoracic mass), but has a diffuse pulmonary abnormality.
Transient tachypnea of the newborn (TTN)
Transient tachypnea of the newborn (TTN) is the most common cause of neonatal respiratory distress. It is caused by lack of clearance of fetal lung fluid.
Normally, prostaglandins dilate pumonary lymphatics to absorb excess fluid. When pulmonary fluid persists, TTN may result. The etiology of the excess fluid may relate to prostaglandin imbalance, potentially worsened by maternal asthma or diabetes, male sex, or Cesarean delivery (lack of vaginal “squeeze”).
Chest radiograph shows pulmonary edema, often with fluid tracking in the minor fissure.
TTN can be clinically and radiographically difficult to differentiate from neonatal pneumonia. Therefore, antibiotics are often given initially, although there is no specific treatment necessary for TTN. TTN resolves spontaneously after a few hours or days.
Respiratory distress syndrome (RDS)/Hyaline membrane disease.
Respiratory distress syndrome (RDS), also called hyaline membrane disease, is the most common cause of respiratory distress in pre-term infants.
RDS is caused by insufficient surfactant (due to immature type II pneumocytes) and resultant decreased lung compliance.
Greater than 95% of cases are seen in pre-term infants born before 34 weeks. Less commonly, term babies born to diabetic mothers have increased prevalence of RDS.
Imaging is characterized by hazy pulmonary opacities, often with air-bronchograms. A key imaging feature that may be seen is decreased lung volumes if the baby is not intubated.
Pulmonary interstitial emphysema (PIE) is a condition often associated with RDS, where barotrauma causes air to dissect through the immature alveoli into the interstitial space and spread along the lymphatic pathways. The radiographic appearance of PIE is hyperinflated lungs with many small cysts representing dissecting air bubbles. PIE may lead to pneumomediastinum or pneumothorax. Special ventilator setting unique to pediatrics, such as high-frequency oscillating ventilation, reduce the severity of PIE.
Bronchopulmonary dysplasia (BPD)/chronic lung disease of prematurity
Respiratory distress syndrome (with or without PIE) lasts for a few days to a week. Beyond that, persistant lung disease is called bronchopulmonary dysplasia, also called chronic lung disease of prematurity.
Bronchopulmonary dysplasia (BPD) is clinically defined as abnormal chest radiograph and persistent need for oxygen at 36 post-conceptual weeks or at 28 days of life, although one may suspect BPD prior to 28 days of life.
Unlike RDS, BPD features mild hyperinflation and coarse opacities.
BPD is the most common cause of chronic respiratory failure in pediatrics.
Meconium aspiration syndrome
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.
Neonatal pneumonia
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.
Congenital diaphragmatic hernia (CDH)
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.
Overview of bronchopulmonary foregut malformation
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.
Congenital lobar emphysema (CLE)
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.
Bronchial atresia
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.
Congenital pulmonary airway malformation (CPAM)/Congenital cystic adenomatoid malformation (CCAM)
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.
Sequestration
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.
Scimitar syndrome
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.
Bronchiolitis
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.
Bronchiolitis obliterans syndrom (BOS) = constrictive bronchiolitis
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.
Cryptogenic organizing pneumonia (COP) = bronchiolitis obliterans organizing pneumonia (BOOP)
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.
Bronchiectasis
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.
Unilateral hyperlucent lung
A unilateral hyperlucent lung is a common finding in pediatric chest radiology. The two most important acute diagnoses are endobronchial foregin body and pneumothorax.
Poland syndrome
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.
Pediatric mediastinal masses
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.
Pneumomediastinum
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.
Plain film evaluation of congenital heart disease
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.
Plain film evaluation of congenital heart disease: Can it be anything else?
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.
Acyanotic congenital heart disease
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.
Cyanotic congenital heart disease
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.
Hypoplastic left heart (HLH)
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.
Extracardiac shunt causing CHF
The two most common lesions to cause neonatal CHF are vein of Galen malformation and hepatic hemangioendothelioma.
Aortic coarctation
Aortic coarctation may cause CHF in infants due to left ventricular obstruction, leading to cardiomegaly and increased pulmonary venous flow.
Acyanotic: shunt vascularity
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
Atrial septal defect (ASD)
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.
Ventricular septal defect (VSD)
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.
Patent ductus arteriosus (PDA)
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.
Endocardial cushion defect (ECD), also called AV canal defect
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.
Ebstein anomaly
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.
Pulmonary atresia with intact ventricular septum
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.
Tetralogy of Fallot (ToF)
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.
Transposition of the great arteries (TGA)
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.
Tricuspid atresia
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.
Truncus arteriosus
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.
Total anomalous pulmonary venous return (TAPVR)
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.
Single (“tingle”) ventricle
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.
Summary of congenital heart disease
Aortic coarctation
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.
Rhabdomyoma
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.
Teratoma
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.
Fibroma
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.
Hemangioma
Similar to teratoma, neonatal cardiac hemangioma is also associated with massive pericardial effusion.
Necrotizing enterocolitis (NEC)
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.
Hypertrophic pyloric stenosis (HPS)
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.
Appendicitis
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.
Malrotation and midgut volvulus
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.
Intussusception
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.
Esophageal atresia and tracheoesophageal fistula (TEF)
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).
Gastric atresia
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.
Neonatal bowel obstruction: Overview
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).
Congenital proximal bowel obstruction
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.
Duodenal atresia, stenosis, and web
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.
Jejunal atresia and stenosis
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.
Congenital low/distal bowel obstruction
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.
Differential diagnosis of microcolon
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.
Meconium ileus
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.
Ileal atresia/colonic atresia
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.
Small left colon/functional immaturity of the colon (FIC)/meconium plug syndrome
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.
Hirschsprung disease
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.
Megacystis microcolon intestinal hypoperistalsis syndrome
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.
Childhood bowel obstruction
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.
Appendicitis (bowel obstruction)
Appendicitis is one of the more common causes of ileus or partial bowel obstruction in children.
Imperforate anus
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.
Terminology of “hemangioma” in pediatric radiology
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.
Differential diagnosis of multiple renal masses
Salter Harris Fractures in Children
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)
Pediatric elbow
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.
Lissencephaly
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).
