|Micrograph of pseudomembranous colitis, a cause of toxic megacolon. H&E stain.|
|Classification and external resources|
Toxic megacolon (megacolon toxicum) is an acute form of colonic distension. It is characterized by a very dilated colon (megacolon), accompanied by abdominal distension (bloating), and sometimes fever, abdominal pain, or shock.
Toxic megacolon is usually a complication of inflammatory bowel disease, such as ulcerative colitis and, more rarely, Crohn's disease, and of some infections of the colon, including Clostridium difficile infections, which have led to pseudomembranous colitis. Other forms of megacolon exist and can be congenital (present since birth, such as Hirschsprung's disease). Also, it can be caused by Entamoeba histolytica and Shigella.
Signs and symptoms
- Abdominal pain
- Abdominal bloating
- Abdominal tenderness
- Tachycardia (rapid heart rate)
There may be signs of septic shock. A physical examination reveals abdominal tenderness and possible loss of bowel sounds. An abdominal radiography shows colonic dilation. White blood cell count is usually elevated. Severe sepsis may present with hypothermia or leukopenia.
The objective of treatment is to decompress the bowel and to prevent swallowed air from further distending the bowel. If decompression is not achieved or the patient does not improve within 24 hours, a colectomy (surgical removal of all or part of the colon) is indicated. When surgery is required the recommended procedure is a subtotal colectomy with end ileostomy. Fluid and electrolyte replacement help to prevent dehydration and shock. Use of corticosteroids may be indicated to suppress the inflammatory reaction in the colon if megacolon has resulted from active inflammatory bowel disease. Antibiotics may be given to prevent sepsis.
Emergency action may be required if severe abdominal pain develops, particularly if it is accompanied by fever, rapid heart rate, tenderness when the abdomen is pressed, bloody diarrhea, frequent diarrhea, or painful bowel movements.
Colonoscopy is contraindicated, as it may rupture the dilated colon resulting in peritonitis and septic shock.
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- This article incorporates text from the United States National Library of Medicine (Toxic megacolon), which is in the public domain.
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- Toxic Megacolon at eMedicine