0521779407-14 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 21:16
962 Megacolon■CT scanning may determine the etiology of megacolon as in the
case of C. difficile infection, where diffuse colonic thickening is a
very sensitive finding
■In toxic megacolon, anemia related to blood loss and leukocytosis
with a left shift occur frequently; electrolyte disturbances (metabolic
alkalosis and hypokalemia) are extremely common. Hypoalbumine-
mia is due to protein loss and decreased hepatic synthesis due to
chronic inflammation and malnutrition. In other cases of mega-
colon, the laboratory findings are unremarkable.
■In Hirschprung’s disease anorectal manometry demonstrates para-
doxical contraction of the internal anal sphincter. Biopsies of the
rectal and colonic wall demonstrate the absence of ganglia provide
a definitive diagnosis.differential diagnosis
■Mechanical obstruction, infection and idiopathic inflammatory
bowel disease are key diagnostic considerations.management
What to Do First
■Plain abdominal films should be obtained immediately. If the patient
is toxic or has peripheral leukocytosis, stool specimens should be
sent for culture, microscopic analysis, and C. difficile toxin. Decom-
press the rectum with an indwelling catheter.General Measures
■Repositioning of the patient results in redistribution of air in the
colon. Intravenous fluids and antibiotics (for toxic cases) should
be administered. Exclude mechanical obstruction (with a hypaque
enema or sigmoidoscopy), discontinue medications that would
adversely affect colonic motility and correct metabolic disturbances.specific therapy
Indications for Treatment
■In toxic megacolon, aggressive therapy of colitis restores normal
colonic motility and decreases the likelihood of perforation. The ini-
tial therapy is medical, which is successful in preventing surgery in
up to 50 percent of patients. Intravenous neostigmine is effective
and safe for acute megacolon.