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In most clinical series, the majority of abdominal masses in neonates are renal in origin. They may be unilateral or bilateral, solid or cystic. After physical examination, evaluation begins with ultrasonography, which is simple and safe to perform. Ultrasonography should define the solid or cystic nature of the mass, determine the presence or absence of normal kidneys, and yield information on other intra-abdominal abnormalities. In selected instances, more involved procedures such as renal scan, computed tomography (CT) scan, retrograde pyelography, venography, and arteriography may be needed to define the problem and plan appropriate therapy.


  1. Multicystic kidney is a form of renal dysplasia and the most common renal cystic disease of the newborn. Fortunately, it is usually unilateral. Ultrasonography can define the nature of the disorder, and CT/nuclear renal scans are useful in assessing the remainder of the urinary system. Nephrectomy is appropriate treatment.

  2. Hydronephrosis. Urinary obstruction, depending on its location, can cause unilateral or bilateral flank and abdominal masses. Treatment is by correction of the obstructing lesion or decompression proximal to it. A kidney rendered nonfunctional by back pressure is usually best removed. Obstructive uropathy may be one category of lesion suitable for in utero intervention. Surgery on the developing fetus to decompress the obstructed urinary system may improve the postnatal status and increase survival. (See Chapter 123.)

  3. Infantile polycystic kidney disease. Inherited in an autosomal recessive fashion, this entity involves both kidneys and carries a grim prognosis.

  4. Renal vein thrombosis. The typical presentation is one or more flank masses and hematuria, usually within the first 3 days of life. Risk factors are maternal diabetes and dehydration. In general, conservative nonoperative management is recommended.

  5. Wilms tumor. See Chapter 122.


Simple ovarian cyst is a frequent cause of a palpable abdominal mass in the female neonate. It presents as a relatively mobile, smooth-walled abdominal mass. It is not associated with cancer, and excision with preservation of any ovarian tissue is curative. Smaller lesions (≤5 cm) may be followed with serial ultrasound until gone over the first year of life as long as they continue to get smaller.


The liver can be enlarged, often to grotesque proportions, by a variety of problems. When physical examination, ultrasonography, and other radiographic studies suggest hepatic origin, magnetic resonance imaging (MRI) or CT should be performed. These studies may be diagnostic and will aid in surgical planning. Lesions include the following:


  1. Hepatic cysts. Congenital solitary non-parasitic cysts of the liver are extremely rare in newborns.

  2. Solid, benign tumors

      1. Hamartomas commonly have a cystic component. They are characterized by fine internal septations without calcifications. Surgical removal or marsupialization of the cysts are options.

  3. Vascular tumors

      1. Hemangiomas of the liver may cause heart failure, thrombocytopenia, and anemia. Therapeutic options include digitalis, corticosteroid administration, embolization, hepatic artery ligation, and liver resection.

      1. Hemangioendothelioma. Now reliably diagnosed with MRI or contrast CT. The infant has normal α-fetoprotein levels. Treatment is reserved only for symptomatic ...

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