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diagnosed only by palpating a large mass through the intact abdominal wall or a
hard fecal mass blocking the anal outlet on rectal examination. Such children may
have a history of encopresis and appear malnourished. Chapter 18 Constipation
covers the diagnostic approach to the child with constipation.
These children should be disimpacted with enemas through a rectal tube passed
above the obstruction, or, if necessary, disimpacted manually. For children unable
to tolerate disimpaction, or those with significant constipation following rectal
disimpaction, oral or nasogastric bowel evacuants such as polyethylene-glycol
electrolyte solution can be used. If the process has progressed to partial bowel
obstruction, either ED or inpatient management is necessary to clean out the
bowel adequately.

Aganglionic Megacolon (Hirschsprung Disease)
In patients with Hirschsprung disease, the parasympathetic ganglion cells of
Auerbach plexus between the circular and longitudinal muscle layers of the colon
are absent. The involved segment varies in length, from less than 1 cm to
involvement of the entire colon and small bowel. The effect of this absence of
ganglion cells produces spasm and abnormal motility of that segment, which
results in either complete intestinal obstruction or chronic constipation.
These children have a lifelong history of constipation, so it is important to
obtain an accurate account of the child’s stool pattern from birth. A child with
Hirschsprung disease typically has never been able to stool properly without
assistance (e.g., enemas, suppositories, anal stimulation). Normal stooling is not
possible because of the failure of the aganglionic bowel and internal anal
sphincter to relax. The child usually has no history of encopresis, as one would
find in chronic functional constipation. These children have chronic abdominal
distension and are often malnourished. Vomiting is uncommon, as are other
symptoms. Complete intestinal obstruction in Hirschsprung disease is more likely
to occur in early infancy and only rarely in the older age groups. It may present
with signs and symptoms of acute bowel perforation.
Table 116.3 summarizes the pertinent diagnostic features differentiating

functional constipation from Hirschsprung disease.
After flat and upright abdominal roentgenogram radiographic studies have
been obtained, a properly performed barium enema with a Hirschsprung catheter
is the best initial diagnostic procedure. There should be no preparation of the
bowel. Ideally, the rectum should not be stimulated by enemas or digital
examination for 1 to 2 days before the procedure. The key to diagnosis is seeing a
“transition zone” ( Fig. 116.16 ) between the contracted aganglionic bowel and
the proximal dilated ganglionated bowel. Stimulation of the rectum shortly before