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Abdominal masses may be found on initial newborn exam but are increasingly identified on prenatal ultrasound. They can arise from peritoneal viscera (solid organs, mesentery, and GI tract) as well as retroperitoneum (kidneys and adrenal glands). Other causes can include obstruction of the urinary system or reproductive organs which can present as an abdominal or pelvic mass. Ovarian cysts are common in the neonatal period.


  1. Intestinal duplications and mesenteric cysts

    1. Majority of congenital gastrointestinal masses.

    2. Present with obstruction or palpable mass, or remain asymptomatic.

    3. Ultrasound shows simple, smooth, cystic lesion.

    4. Treatment is surgical resection.

  2. Meconium cysts

    1. Associated with in utero perforation.

    2. See Chapter 72.


  1. Smaller masses are usually found incidentally. Larger masses may present with hepatomegaly or palpable right upper quadrant lesion. Evaluation begins with ultrasound, followed by cross-sectional imaging (MRI or CT scan) for better definition, diagnosis, and surgical planning.

  2. Cystic lesions

    1. Hepatic cysts

      1. Benign lesions; occur in 2.5% of newborns.

      2. Majority are asymptomatic.

      3. May be complicated by infection or rapid growth, resulting in abdominal pain and compressive symptoms.

      4. Resection reserved for symptomatic lesions.

      5. Multiple cysts may be associated with polycystic liver and kidney disease.

    2. Choledochal cysts (biliary cysts)

      1. Originate from bile ducts, resulting in abnormal dilation of biliary tree with an incidence of 1 in 100,000 to 150,000. There is a male-to-female ratio of 1:4.

      2. Present with cholangitis or biliary obstruction, but may remain insidious. May cause direct (conjugated) hyperbilirubinemia with jaundice. Management is discussed further in Chapter 62.

      3. Surgical resection recommended due to 30% lifetime risk of cholangiocarcinoma.

  3. Solid lesions

    1. Hemangioendotheliomas

      1. Most common benign hepatic neoplasm in children.

      2. When large, may result in consumptive coagulopathy and thrombocytopenia (Kasabach-Merritt syndrome) and high output heart failure.

      3. Majority undergo spontaneous regression with treatment reserved for symptomatic lesions.

      4. Systemic therapy with interferon, corticosteroids, or vincristine may be attempted. Angioembolization, segmental resection, and liver transplantation have been described for refractory neoplasms.

    2. Hamartoma

      1. Is the second most common benign liver neoplasm in the pediatric age group. Larger lesions can cause neonatal respiratory distress and/or circulatory complications relating to intra-abdominal space-occupying lesion.

      2. Imaging shows multiseptated lesions with a cystic component and minimal vascularity.

      3. Liver function studies and α-fetoprotein are typically normal.

      4. Excision or marsupialization may be pursued.

    3. Hepatoblastoma

      1. Most common hepatic malignancy in neonates.

      2. Premature very low birthweight infants are at higher risk. Associated conditions can include Beckwith-Wiedemann syndrome, hemihypertrophy, and thrombocytosis.

      3. Diagnosis made with imaging and elevated serum α-fetoprotein.

      4. Biopsy may be needed to guide chemotherapeutic protocols for lesions that are not immediately resectable.

      5. Cisplatin and doxorubicin and surgical resection remain the mainstay of therapy, resulting in improved cure rates.

      6. Hepatic transplantation is indicated for unresectable lesions and associated with improved survival.


  1. Majority of neonatal abdominal masses arise from kidney.

  2. May be unilateral or bilateral, and solid or cystic....

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