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 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 to 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