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Necrotizing Enterocolitis

Who does it affect? What causes it?

Mortality rate?

Initial radiographic finding? What part of the bowel is usually involved?

What could be seen later in disease?

What is the "football" sign?

Early NEC can be treated how? What if pneumoperitoneum is present?

What is the most common delayed complication? How would you evaluate this?

  • Necrotizing enterocolitis - NEC affects pre-term infants and is thought to be caused by a combination of infection and ischemia related to feeding. Although NEC is typically seen in premature infants, it may also occur in term infants with congenital heart disease, on immunosuppression, or with an umbilical venous catheter. Mortality can be up to 30%.
  • 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 the disease, pneumatosis, portal 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

What is it? Classic presentation?

Who gets it?

What is the "caterpillar" sign?

US criteria? Important pitfall?


Main differential consideration? How do you tell?

  • 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 cause 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 differential 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.


Pediatric Appendicitis

Does this get surgery?


First test of choice? Imaging appearence?

When would you use CT?

  • 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 high clinical suspicion for appendicitis. The CT findings of appendicitis in children are identical to those in adults.


Malrotation and Midgut Volvulus

What is it? Why is volvulus so important to diagnose?

Presentation? At what age do they present? How do you rule it out?

Can you have malrotation without volvulus?

Classic upper GI finding?


  • 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.
    • 75% of infants with malrotation present within the first month of life and 90% become symptomatic within one year.
  • 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.
  • The classic upper GI finding of midgut volvulus is the corkscrew appearance of twisted bowel.


In normal embryologic development, the bowel rotates ______ degrees in the _______wise around the ______ artery causing the characteristic retroperitoneal course of which structure?

  • In normal embryologic development, the bowel rotates 270 degrees counterclockwise around the superior mesenteric artery, causing the characteristic retroperitoneal course of the duodenum.


What are the two most important relationships to demonstrate on every upper GI series?

What view is and where is the normal DJJ?

  • 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).


Provide some clues to identify the presence of malrotation without volvulus

  • 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 to the right of the SMA).
  • Color doppler ultrasound or CT studies of the twisted mesenteric vessels demonstrate the wwhirlpool sign.


What is the Ladd procedure?

What is done to the bowel? 

What other procedure may be performed at same time?

  • Treatment of malrotation with volvulus
  • 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.



What is it?

Most common location?

Classic presentation?

Etiology in children between 3 months and 3.5 years? How about children in older than 3.5 years?

Primary modality for diagnosis? Appearance?

  • 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,” and 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 often have a pathologic lead point, which may be an intestinal polyp, meckel diverticulum (infants), or lymphoma (children).
  • Radiographs are nonspecific, but may show a soft tissue mass in the right lower quadrant.
  • Ultrasound is the primary modality for diagnosis, which shows a characteristic target or pseudokidney sign with alternating layers of bowel wall and mesenteric fat.


Significance in incidental short segment intussusception in older children or adults?

  • A transient, asymptomatic, incidental, short segment intussusception in older children or adults seen on CT performed for another reason is likely clinically insignificant.


DDx of bloody stool and thick-walled bowel on US

  • The differential diagnosis of bloody stool and thick-walled bowel on ultrasound includes:
    • Intussusception
    • Colitis
    • much less commonly intramural hematoma (e.g., due to trauma or Henoch-Schönlein purpura).


First line treatment for intusussception?


  • The first line of 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

What is it? Why does it happen?

50% of patients with TEF have what association?

Classic radiographic finding of a type A?

How may a type B TEF look on radiograph?

What is the type H? How might this present?

What makes you think of esophageal atresia in utero?

What other trachial anomalies are associated with 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 tracheoesophageal fistula.
  • 50% of patients with TEF have associated anomalies, most commonly the VACTERL association.
  • 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 without fistula.
  • The H type ~6% features a continuous esophagus without esophageal atresia, but with an 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).


What is the VACTERL association?

  • Vertebral segmentation anomalies.
  • Anal atresia.
  • Cardiac anomalies.
  • TracheoEsophageal fistula.​
  • Renal anomalies.​
  • Limb (radial ray) anomalies.


Gastric Atresia

What is it?

How does it present?

Contrast to HPS

Diagnostic imaging finding

What is the less severe variant?

  • 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

Compare to childhood or adult obstruction. Role of CT?

Can you distinguish between large and small bowel?

How do you divide the DDx of bowel obstruction in neonates?

Treatment for proximal obstruction? What must be ruled out?

Specific goal of imaging for distal obstruction?

If the initial radiograph does not provide a definitive diagnosis, what is the imaging test of choice for proximal obstruction?

How do you get a definitive dx of duodenal atresia?

Subsequent to radiograph what is the test of choice for a distal obstruction?

Describe what you see in the image provided.

  • 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 plays 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 definite 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.
  • Neonatal distal bowel obstruction: Abdominal radiograph shows numerous dilated loops of bowel throughout the entire abdomen. A nasogastric tube is in the stomach.


What are the congenital proximal bowel obstructions?


Role of imaging?

  • 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.
    • Malrotation and midgut volvulus
    • Duodenal atresia, stenosis, and web
    • Jejunal atresia and stenosis


Duodenal Atresia, Stenosis and Web

How do they form? 

What is the "windsock" sign signify?

In what scenario can you see distal bowel gas in a case of complete duodenal atresia?

What is the classic radiographic appearance of duodenal atresia?

  • 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 get 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 gas can travel through the ampulla of Vater and enter the distal bowel.
  • 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.


Duodenal anomaly associations

Seen in what percent of patients with duodenal anomalies?

Most common association with duodenal atresia?

List the other associations.

  • 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:
    • Shunt vascularity cardiac lesions (ASD, VSD, PDA, and endocardial cushion defect)
    • Malrotation 
    • Annular pancreas, which is seen in 20% of babies with duodenal atresia.


What is the diagnosis for the double bubble sign without distal bowel gas?

What is the DDx for the double bubble sign with the presence of distal bowel gas?

  • 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)
    • less severe variants of duodenal atresia including duodenal stenosis and web.


Jejunal Atresia and Stenosis

In contrast to duodenal atresia, what causes this?

Jejunal atresia or stenosis is more common?

What radiographic sign is suggestion of jejunal atresia?

  • 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.


A contrast enema in neonates or children is performed with what specific contrast?

Why is this significant?

  • When performing a contrast enema, isotonic or mildly hypertonic water-soluble contrast is used, such as a 17% solution of Cysto-Conray II (400 mOsm) or Covidein.
  • High osmolar contrast may cause fluid shifts and resultant destabilization of the patient.


DDx of Microcolon

What is a microcolon? What prevents microcolon if there is a proximal bowel obstruction?

What are the two most common causes?

What is seen in association with meconium ileus?

Contrast meconium ilieus with small left colon syndrome.

Does jejunal atresia cause microcolon?

Does segmental Hirschprung cause 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.
  • Peritoneal/scrotal calcifications may be seen in association with meconium ileus. In contrast to meconium ileus, small left colon syndrome (also confusingly called meconium plug syndrome - does NOT cause a microcolon).
  • Jejunal atresia does NOT cause microcolon as there is enough succus entericus produced to nourish the colon. Total colonic Hirschsprung is rare. The much more common segmental involvement does not cause microcolon .


Meconium Ileus

What is it? What is a possible complication and what imaging finding can that lead to?

Meconium ileus is the earliest manifestation of what disorder? How many patients with meconium ileus have this disorder?

Classic radiographic appearence of meconium illeus?

What does contrast enema show?



  • 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), with 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 a 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

Lower GI enema feature?

Prevalence of colonic atresia?

Contrast to meconium ileus

  • 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

What is it?


Seen in which population?


Radiograph appearance? Contrast enema appearance? 

Primary DDx consideration? Contrast this to it


  • 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, small left 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.


Hirschsprung Disease

What is it? Cause? What part of the colon is always affected? Ranges of severity?

1/3 of cases develop a form of what disease? What is the fulminant form?

5% of patients with Hsprung disease have what association?

Radiographic appearance? 

Contrast enema appearance? Best seen on what view?

What can be seen in the rectum is involved?

Contrast to functional immaturity of the colon.

Definitive diagnostic test? Treatment?




  • 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.


What is megacystic microcolon intestinal hypoperistalsis syndrome? Prognosis?

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


Can malrotation cause distal obstruction?

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


Childhood Bowel Obstruction

Compare to adult bowel obstruction

What are the most common causes of childhood bowel obstruction?

What is one of the more common causes of ileus or partial bowel obstruction in children?

How are they treated?

  • 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.


Inguinal Hernia in Childhood Causing Bowel Obstruction

What are indirect inguinal hernias due to?

Imaging finding?

What risk is inherent in irreducible hernias?

  • 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.


Anorectal Malformations

What is the role of radiological imaging of imperforate anus?

What differentiates high vs low lesions?

What are high lesions associated with? Treatment?

What are low lesions associated with? Treatment?

How do you tell between low and high lesions?

What imaging modality is used to differentiate between high vs low lesions?

  • 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.


Neonatal Cholestatic Jaundice

What type of jaundice is never normal?

What are some causes of the "never normal" kind of jaundice?

What is the goal of imaging in neonatal cholestatic jaundice? What entity makes up 25% of neonatal cholestatic jaundice?

What is "neonatal hepatitis"?

What is the test of choice? 

Do you have to do anything before this test of choice?



  • In contrast to the unconjugated hyperbilirubinemia of the benign and self-limited physiologic jaundice of the newborn, conjugated hyperbilirubinemia is never normal and is due to hepatic or biliary dysfunction.
  • There are innumerable causes of conjugated hyperbilirubinemia, including biliary atresia, Alagille syndrome, bile acid synthetic defects, metabolic disease, alpha-1-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.


Neonatal Hepatitis

What is seen on hepatobiliary scintigraphy in neonatal hepatitis?

What imaging appearance would rule out biliary atresia?

  • 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.


Pediatric Hepatobiliary Neoplasia and Masses

How is primary pediatric liver tumors classified pathologically?

Liver mets may be seen in the setting of what entities?

How do you narrow the DDx in primary liver tumors?

What benign epithelial lesions are seen in peds and also adults?

  • 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.


Mesenchymal Hamartoma

What is it? What kind of tissues does it contain?

Is this a neoplasm?

When do children present?

Contrast to hepatoblastoma?

Imaging appearance? What is rarely seen in these "tumors"?


  • 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.


What are the cystic liver/biliary masses?

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


Choledochal Cysts/Caroli Disease

What are choledochal cysts?


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


What is gallbladder hydrops?

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


Classification of Pediatric Vascular Malformations and Neoplasms

How are these categorized? What's the difference between them?

How do you further classify vascular anomalies? What are the entities in each group?

What does the term "hepatic hemangioma" refer to?

What is the adult hemangioma in this context?

What are the soft tissue "hemangiomas" of Maffucci syndrome in this context?

What are the high-flow vascular neoplasms?

  • 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.


What are the pediatric solid liver/biliary masses?

  • Infantile Hemangioma / hemangioendothelioma
  • Hepatoblastoma
  • HCC
  • Undifferentiated embryonal sarcoma (malignant Mesenchymoma)
  • Metastatic disease



Infantile Hemangioma / Hemangioendothelioma

What are these? What can these cause in 25% of cases?

Tumor marker elevation?

Which one is benign? Which one has potential to met?

Associated syndrome?

Imaging Appearance? Classic Angiographic finding?

Clinical outcome? Treatmet?

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



What is it? Prevalence relative to other childhood abdominal malignancy?

When do they occur compared to those affected by infantile hemangioma or mesenchymal hamartoma? How many cases present in the neonatal period?


Classic radiographic finding?

Cross-sectional imaging appearance?

  • Hepatoblastoma is a malignant embryonal neoplasm that is the most common liver tumor of early childhood and the third most common childhood abdominal malignancy overall (third to neuroblastoma and Wilms tumor).
  • Hepatoblastoma occurs in children slightly older than those affected by infantile hemangioma and mesenchymal hamartoma. Less than 10% of cases occur during the neonatal period.
  • Hepatoblastoma is associated with several genetic anomalies and syndromes, including:
    • Beckwith-Wiedemann (Q6 month screening ultrasound screening is performed).
    • Familial adenomatous polyposis syndrome.
    • Fetal alcohol syndrome.
  • 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.


Pediatric HCC

Usually seen in what setting?

Pediatric causes of this setting?

Tumor marker elevation?

Imaging appearance? What does this tumor have a propensity to do?

  • 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.


Undifferentiated Embryonal Sarcoma (Malignant Mesenchymoma)

What is it? What age group does it occur?

Tumor markers?

  • 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.


Which tumors are common pediatric with a propensity to metastasize to the liver?

  • 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.


Meckel's Diverticulum

What is it?

Most common manifestation in children? Less common presenation in children?

Most common presentation in adults?

What does the omphalomesenteric duct connect? What can result in incomplete regression of the omphalomesenteric duct? What is the most common thing that happens?

Where is the Meckel located? Whats the "rule of 2s"

How do you diagnose a bleeding meckel? Which Meckls bleed and what percent of them have this special feature?

  • 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 Meckel contains ectopic gastric mucosa; however, these are the Meckels that are most likely to bleed.
  • Approximately 50% of Meckels contain ectopic gastric (less commonly pancreatic) mucosa. on pertechnetate scan, uptake kinetics of the ectopic mucosa is equal to gastric mucosa.


What is the entire spectrum of meconium pathologies!?

What causes meconium peritonitis?

What is the radiographic appearance of meconium peritonitis?

  • 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.


Pediatric Abdominal Calcifications

What is their significance?

  • 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).


Vesicoureteral Reflux

What is it? What does it predispose to? Long-term complication?


Typical imaging evaluation?

What about siblings of patients with VUR?

The goal of treatment?

Treatment? Specific treatments for grading?

What grades regress and what percent of them?


  • 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.


VUR Grading

Describe grades I - IV


  • 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.


Vesicoureteral Reflux

Preferred initial study? Why?

What are two nuclear studies often used for eval and follow-up of reflux?

The grading system of the nuclear scan?

  • 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.


Duplex Collecting System

Contains what two structures?

What is the clinical significance?

What is the Weigert-Meyer rule?

Why couldn't you see a completely obstructed system on VCUG?

What is the "drooping lily" sign?

DDx for "drooping lily"? How to tell the difference?

  • A duplex collecting system contains two separate pelvicalyceal systems and two ureters. A duplex system may be of no clinical significance if the ureters fuse. However, if the ureters insert separately into the bladder, there is an increased risk of obstruction (in the upper pole moiety) and reflux (in the lower pole moiety).
  • The Weigert–Meyer rule: In a duplicated system, the upper pole ureter inserts ectopically (inferomedially) into the bladder and is prone to obstruction, often due to a ureterocele. The lower pole ureter inserts orthotopically (normally) but is prone to reflux
    • WeIgert-Meyer - Weigert-Meyer were high class (upper pole of kidney)IinferoMedially and ectOpic, Obstructed, uretOcele. 
    • 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.


What is the most common cause of unilateral hydronephrosis in children?

What are some causes?

  • 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.


What is the most common cause of congenital bladder outlet?

What is it caused by?

Characteristic US finding?

Main DDx consideration? How to tell the difference?

  • 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.


Prune Belly Syndrome

What is it?

What may it be associated with?

What does it lead to in the collecting system? 

Contrast to posterior urethral valves?

  • 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.


Uretocele (UVJ Obstruction)

What is it?

An ectopic uretocele is almost always associated with what?

A simple uretocele is seen in what setting?

Typical US appearance? 

VCUG appearence of uretocele?


  • 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.


What are the anatomic locations for various causes of hydronephrosis or hydroureter?

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


What is the most common cystic abdominal mass in a neonate?



What is the most common neonatal cystic renal mass? What is it characterized by?

Is it unilateral or bilateral?

Natural progression?

Does it have an association with Wilms tumor?

US imaging appearance? Difference between this imaging appearance and hydronephrosis. 

  • 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.


Pediatric Simple Renal Cyst

How often do we see isolated simple renal cysts?

When seen, what two associations should we consider?

In addition to simple renal cysts, patient may have what other findings in each of these associations?

  • 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.


Multilocular Cystic Nephroma

What is it?


Imaging appearance and what tumor does it mimic? Characteristic imaging finding?

  • 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.


Autosomal Dominant Polycystic Kidney Disease

When does it manifest?

What percent of patients develope some cysts in the first decade of like?

What other cysts can you find in these patients?

  • 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.


Autosomal Recessive Polycystic Kidney Disease

Imaging appearance?

What may determine a worse prognosis?

Fetal diagnosis may cause what to the fetus during pregnancy?

What is associated with ARPKD, especially when it manifests later in childhood?

  • 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.


Wilms Tumor

What is it? Who does it typically affect? What tissue does it arise from?

Which patients have an increased risk of Wilms tumor? Describe each entity. What extra imaging do they need?

Classic imaging appearance? +/- Calcifications? A cystic Wilms may mimic what benign entity?

Does Wilms metastasize? If so, how often and where to?

  • 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.


Pediatric RCC

  • 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.


What are the pediatric malignant solid renal masses?

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


What are the pediatric benign solid renal masses?

  • Mesoblastic nephroma
  • Nephroblastomatosis
  • Angiomyolipoma


Wilms Tumor Staging

What is the name of the staging system?

What are the stages? Survival rates of each stage?

  • 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.


Rhabdoid Tumor

What is it?

Where can it occur? Can they occur concurrently?

Imaging appearance?


  • 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.


What is an uncommon solid renal cell cancer with a propensity to metastasize to bone?

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


Renal Metastases

What are the most common primary malignancies to metastasize to the kidneys in children?

How does leukemia characteristically metastasize to kidneys?

What are some imaging presentations of lymphoma within the kidneys?

  • 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.


Mesoblastic Nephroma

What is it? Appearance-wise, what is it identical to? Who does it occur in?


What tissue does it arise from?

What should you not confuse this entity with?

  • 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.



What is it? What is the term used with this tissue persists beyond 36 weeks?

Imaging appearance? Common findings?

Why are these screened frequently?

Worrisome findings on screening?

  • 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.



What is it? What tissues does it contain?

Multiple AMLs are associated with what?

Most AMLs have what characteristic imaging feature?

What is the concern with AMLs?

  • 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.


DDx for Multiple Renal Masses

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


Metanephric Blastema

What is this?

What can occur if this stays persistent?

What entity is not related to metanephric blastema?

  • 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.


What are the adrenal mass lesions?

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



What is it? Where does it arise from?

Mean age of diagnosis?

Typical CT appearance?

MRI appearance?

Positive on what nuclear medicine scan?

How often does it metastasize and to where? How does it metastasize? What is a classic presentation of  metastatic neuroblastoma?

  • 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.


Neuroblastoma Staging

What is considered "midline"

What are the stages of neuroblastoma and the two-year survival rates of each stage?

  • 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%


Ganglioneuroma and Ganglioneuroblastoma

What are these?

Contrast to neuroblastoma on affected population and imaging appearance

  • 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.


Neonatal Adrenal Hemorrhage

How is it typically diagnosed? What does it look like? What entity could it look like?

What would follow up scans show?

  • 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.


Adrenal Cortical Carcinoma


Who does it affect?



  • 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.


Pediatric Cystic Pelvic Masses (in Either Sex)

What is a urachus? What does it connect?

There is an increased risk of what if a urachal anomaly is not resected?

What are the types of urachal anomalies? Which one is most common?

What is a rectal duplication cyst? Where do they usually occur? Treatment?

  • 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.


What does the DDx for cystic pediatric pelvic masses depend on?

What are they most likely due to?

  • 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.


What cystic pelvic masses are seen only in girls?

  • 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.


What are the cystic pelvic masses seen in only male children?

Describe each one.

  • 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.