0521779407-14 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 21:16
Megacolon 961Symptoms
■In acute megacolon bloating, obstipation and abdominal pain are
the main symptoms. In cases of toxic megacolon, signs and symp-
toms of acute colitis precede the onset of acute dilation. Improve-
ment of diarrhea may herald the onset of megacolon. Chronic
megacolon usually presents with constipation and abdominal full-
ness.Physical Signs
■The general physical examination is not helpful in most patients pre-
senting with chronic constipation and megacolon. In acute mega-
colon (Ogilvie’s syndrome) pronounced abdominal distention with
generalized abdominal tenderness is noted. In toxic megacolon,
physical examination reveals an ill-appearing patient with tachy-
cardia, fever, hypotension, abdominal distension and tenderness,
with or without signs of peritonitis.tests
Basic Tests
■Plain abdominal radiographs are critical for diagnosis and follow-
up. Multiple air-fluid levels in the colon are common. The normal
colonic haustral pattern is either absent or severely disturbed and
significant stool is evident.Specific Diagnostic Tests
■Flexible sigmoidoscopy and colonoscopy help identify lesions that
narrow or occlude the bowel. Colonoscopy is extremely risky in
patients with toxic megacolon. If needed for decompression, only
minimal amounts of air should be introduced into the colon to avoid
perforation. A guidewire is placed through the colonoscope and a
decompression tube is then passed into the right colon.Other Tests
■Barium enema is less costly and may be preferable in detecting
megacolon and megarectum. Barium radiographs may also show
the aganglionic distal bowel with proximal dilatation of the colon in
classic Hirschsprung’s disease. Although anorectal manometry may
provide useful information in patients with severe constipation, it
has no value in the assessment of acute megacolon. Colonic transit
studies are important for cases of chronic megacolon due to colonic
inertia.