GI/GU Flashcards

Question

Ileal Atresia / Colonic Atresia Lower GI enema feature? Prevalence of colonic atresia? Contrast to meconium ileus

Answer 1

* 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 2

* 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, neonates born to mothers who received magnesium for (pre)eclampsia, and infants born to diabetic mothers.** * Infants with smal left colon **are almost always otherwise normal****.** * In **contrast to meconium ileus, sm****all l****eft colon is not a cause of** **microcolon****.**Small left colon is**not associated with cystic fibrosis/meconium ileus** despite the confusing 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 3

* 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 to 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 Hirschsprung disease 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, caused an abnormal rectum:sigmoid ratio 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 cause a tapered, rather than an abrupt, transition zone.** * Definitive diagnosis is with **suction biopsy of the bowel wall.** **Treatment is surgical.**

Answer 4

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

Answer 5

* Although uncommon, the Ladd bands of malrotation may cause a distal obstruction.

Answer 6

* 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 **AAIIIMM** (appendicitis, adhesions, internal/inguinal hernia, intussusception, ilieitis (terminal ie Crohn's), Meckel's, and malrotation). * Appendicitis is one of the more common causes of ileus or partial bowel obstruction in children. * Most causes of childhood obstruction are **treated surgically.**

Answer 7

* 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 8

* 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 complex 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 the urine = high lesion. * In females, if meconium is passed in the vagina and a fistula is not visualized = high lesion. Low lesions may 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 9

* In c**ontrast 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-antitrypsin 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 diagnosis 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 10

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

Answer 11

* Primary pediatric liver 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), the age of the patient, and tumor markers (AFP and endothelial growth factor).** * Benign epithelial lesions also seen in adults include **focal nodular hyperplasia and adenoma.**

Answer 12

* Mesenchymal hamartoma is a **benign, multicystic, hamartomatous liver 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 typically 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 that the mass appears solid**. When **large, the mass may displace vasculature.** * Surgical **resection is almost always curative.**

Answer 13

* Mesenchymal hamartoma * Choledochal cyst/Caroli's dz * Gallbladder hydrops

Answer 14

* Choledochal cysts (including Caroli disease) represent saccular or fusiform dilation of bile ducts, which may be segmental or diffuse. * Todani classification (check GI section)

Answer 15

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

Answer 16

* 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 17

* Infantile **H**emangioma / hemangioendothelioma * **H**epatoblastoma * **H**CC * Undifferentiated embryonal sarcoma (malignant **M**esenchymoma) * **M**etastatic disease MNEMONIC: HHHMM

Answer 18

* Infantile hemangioma and hemangioendothelioma are r**elated 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.** * Infantile hemangioma is associated with Kasabac**H**-Merrit syndrome, which is a syndrome of vascular neoplasm (**H**emangioma), **H**emolytic 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 in the first year of life, especially if GLUT-1 positive. Propranolol may accelerate involution.** * **Surgery may be necessary for lesions causing CHF.**

Answer 19

* Hepatoblastoma is a **malignant embryonal neoplasm that is the most common liver tumor of early childhood** and the t**hird 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 screening is performed). * **Familial adenomatous polyposis syndrome.** * **Fetal alcohol syndrome.** * MNEMONIC: BFF * Alpha fetoprotein - **AFP is elevated.** * A classic radiographic finding of hepatoblastoma is **right upper quadrant calcification.** * Cross-sectional imaging shows a **heterogeneous, predominantly solid, enhancing liver mass, which demonstrates a propensity for portal vein and hepatic vein invasion.**

Answer 20

* Similar to adults, hepatocellular carcinoma - HCC is **usually seen in the background of cirrhosis.** * Pediatric causes of cirrhosis include **_alpha-1-antitrypsin deficiency, 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 heterogeneous hepatic mass with early arterial enhancement and rapid washout**. Similar to hepatoblastoma, HCC also **commonly demonstrates venous invasion.**

Answer 21

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

Answer 22

* **Wilms tumor and neuroblastoma** are common pediatric tumors with a propensity to metastasize to the liver. * Makes sense Wilms and neuroblastoma are the two most common pediatric abdominal masses.

Answer 23

* Meckel diverticulum is an **omphalomesenteric duct remnant**. In young children, the most common manifestation of a Meckel diverticulum is **gastrointestinal bleeding** (if the Meckel contains 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 2s” 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 M****eckel****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 24

* **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 symptom 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 calcification, and meconium pseudocyst formation.

Answer 25

* Abdominal calcification 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 26

* Vesicoureteral reflux (VUR) is **abnormal retrograde reflux of urine from the bladder into the ureter, which predisposes to acute 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**. Renal ultrasound is not sensitive for the detection of reflux, although some institutions perform an ultrasound as a screening modality. Recent studies suggest that approximately 5% of children with a UTI and a normal ultrasound have VUR. * **Siblings 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 often is treated surgically.** * Approximately **90% of grade I and II reflux will spontaneously regress after a few years.**

Answer 27

* I: Reflux into ureter only, with normal ureteral and calyceal morphology. * II: Reflux into non-dilated renal calyces, with normal ureteral and calyceal morphology. * III: Reflux into the renal collecting system, with blunting of the calyces (loss of normal “spiky” appearance of calyces). * IV: Reflux into a moderately dilated ureter. * V: Reflux into severely dilated and tortuous ureter * Grades I-III are initially treated medically (prophylactic antibiotics). * Higher grade reflux often is treated surgically. * Approximately 90% of grade I and II reflux will spontaneously regress after a few years.

Answer 28

* **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: * **Radionuclide cystogram** - RNC involves the instillation of approximately 1 mCi of Tc-99m-pertechnetate 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 29

* A duplex collecting system c**ontains 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).** * 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 l**ower pole ureter inserts orthotopically (normally) but is prone to reflux**. * We**I**gert-**M**eyer - Weigert-Meyer were high class (upper pole of kidney)**I**infero**M**edially and ect**O**pic, **O**bstructed, uret**O**cele. * The lower pole is the orthotopic (normal) and is prone to the other thing that the ectopic one isn't (ie not obstruction but 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 lily sign is seen on VCUG where the “invisible” obstructed 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 contrast, the **obstructed upper pole of the drooping lily has fewer calyces.**

Answer 30

* **Ureteropelvic 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 31

* **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 (prostatic) 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 32

* Prune belly syndrome is a **congenital muscular disorder that affects the abdominal wall musculature and the smooth muscles of 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 33

* 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 ureteroceles are almost always located inferior and medial to the lower pole ureteral insertion site. * **VCUG typically shows the ureterocele as a rounded filling defect.**

Answer 34

* UPJ - Obstruction * UVJ - Relfux and obstruction (uretocele) * Urethra - Posterior urethral valves and neurogenic bladder

Answer 35

Hydronephrosis

Answer 36

* 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 urinary obstruction.** * MCDJ is **typically unilateral, but bilateral abnormalities may be present in 20-30% of cases.** * 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 37

* 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 rhabdomyoma. * 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 38

* Multilocular cystic nephroma is a **benign, multiseptated cystic neoplasm. It has a bimodal age distribution, seen in _young boys 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 39

* 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 40

* 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, producing a characteristic appearance on ultrasound of _bilaterally enlarged, echogenic kidneys._** * **Earlier presentations have a 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 41

* 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 blastema.** * **Patients with increased risk for Wilms tumor are screened with regular ultrasound until school age**, and include patients with: * **Beckwith-Wiedemann syndrome** (hemihypertrophy, macroglossia, omphalocele, neonatal hypoglycemia (due to insulin overproduction by pancreatic beta-cells), and increased risk of childhood malignancies, including Wilms tumor and hepatoblastoma). * **WAGR syndrome** (Wilms tumor, aniridia, genitourinary anomalies, and mental retardation). * **Horseshoe kidney**: Approximately 2x incidence of Wilms tumor. * **Trisomy 18**. * The classic imaging appearance of Wilms is a **heterogeneous, 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 nephroma.** * **Liver or lung metastases are each seen in approximately 10%, and bone metastases (typically lytic) are seen in approximately 5% of cases.**

Answer 42

* 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 43

* Wilms tumor * RCC * Rhabdoid tumor * Clear cell sarcoma * Renal metastasis

Answer 44

* Mesoblastic nephroma * Nephroblastomatosis * Angiomyolipoma

Answer 45

* 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 structures (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 46

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

Answer 47

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

Answer 48

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

Answer 49

* 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 50

* Nephroblastomatosis is the **persistence of metanephric blastema**. The term **nephrogenic rest** is used when metanephric blastema persists beyond 36 weeks gestation. * On imaging, nephroblastomatosis **may appear as a discrete, homogeneous,** **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 51

* 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 52

* Nephroblasomatosis * Lymphoma * Multifocal Pyelonephritis (fever?) * Multiple Infarcts (sickle cell disease?)

Answer 53

* 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 metanephric blastema persists after embryogenesis, it can lead to: * **Nephroblastomatosis**, which is benign persistent metanephric blastema manifesting as single, multiple, or confluent homogeneous renal masses. Nephroblastomatosis has an increased risk of Wilms tumor. * **Mesoblastic nephroma**, a benign tumor that arises from persistent metanephric blastema. Its appearance mimics Wilms but it occurs in neonates. * **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. * _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 54

* Neuroblastoma * Ganglioneuroma and Ganglioneuoblastoma * Adrenal Hemorrhage (in neotates) * Adrenal Cortical Carcinoma

Answer 55

* 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 of metastatic neuroblastoma is an **intracranial, subdural mass originating from the marrow.**

Answer 56

* 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 crossing midline. * Two-year survival: 75% * Stage III : Local spread, crosses midline. * Two-year survival: 25%s * Stage IV : distant metastases. * Two-year survival: 25% * Stage 4S : Stage I or II with metastases confined to 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 57

* 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).** * _50% of ganglioneuromas are positive on I-123 MIBG scintigraphy_. * MRI classically _shows restricted diffusion of a neuroblastoma, but not in ganglioneuroma._

Answer 58

* 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 59

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

Answer 60

* 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 61

* 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 62

* **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. * **Hematometrocolpos:** 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 63

* A Müllerian duct cyst is caused by incomplete regression of the Müllerian ducts. In a normal male, the Mullerian ducts regress. **A persistent Müllerian duct remnant can cause a Müllerian duct cyst.** * In a normal female, Müllerian 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 Müllerian duct**. _It arises from the posterior urethra near the verumontanum_ (ridge of the posterior urethra near the seminal vesicle insertion). _When associated with hypospadias (urethra opens along the ventral penile shaft), a prostatic utricle can become very large._

GI/GU Flashcards

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