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The abdominal mass in an infant or child is most commonly an
incidental finding first observed by a parent or at the time of
a pediatric screening examination. Over 50% of abdominal
masses detected by physical examination are actually cases of organomegaly.1,2 The
remaining 43% of masses require surgical evaluation and
comprise neoplasms, developmental anomalies, and inflammatory or
infectious disease. Ninety percent of this group are retroperitoneal
masses, approximately half of which derive from the urinary tract.2 In
neonates, multicystic dysplastic kidney and hydronephrosis occur
in equal frequency and comprise 75% of abdominal masses.2 Older
children are more likely to have neoplastic processes.2Table 388-1 lists the most likely diagnoses
that vary by location of the mass and age group.
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Most masses are asymptomatic, so the history is rarely diagnostic.
Signs and symptoms concerning for malignancy include increased abdominal
girth, associated abdominal pain, pain with movement or palpation,
constipation, or change in pattern of urination.1 Other
helpful elements in the history include signs or symptoms of intestinal
obstruction, jaundice, fever, and weight loss. The approximate location
of the mass; its mobility, size, and consistency; and any associated
developmental anomalies should be noted on physical examination
and may be helpful when discussing initial imaging modalities with
the radiologist. Ultimately, the age of the patient and physical examination
findings narrow the differential diagnosis prior to radiologic imaging.
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The radiologic evaluation of the neonatal abdominal mass should
begin with abdominal plain films to rule out gastrointestinal obstruction.
In contemporary practice, an increasing number of neonatal masses ...