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Toxic megacolon



Toxic megacolon is a life-threatening complication of other intestinal conditions that causes rapid widening (dilation) of the large intestine within 1 to a few days.

Alternative Names

Toxic dilation of the colon; Megarectum


Toxic megacolon occurs as a complication of inflammatory bowel disease, such as ulcerative colitis and Crohn’s disease, and infections of the colon. The term "toxic" means that this complication occurs with infection or inflammation.

This is not the same as other forms of megacolon, such as pseudo-obstruction, acute colonic ileus, or congenital colonic dilation. These conditions occur without infection or inflammation.


The rapid widening of the colon may cause the following symptoms:

Signs and tests

The rapid widening (dilation) of the colon makes this different from other conditions, such as chronic constipation, that can widen the colon slowly and do not cause sudden, life-threatening symptoms.

A physical exam may reveal signs of septic shock. The doctor will notice tenderness in the abdomen and possible loss of bowel sounds.


Support Groups

Expectations (prognosis)

If the condition does not improve, there is a significant risk of death. In this case, a colectomy is usually needed.

Calling your health care provider

Go to the emergency room or call the local emergency number (such as 911) if you develop severe abdominal pain -- especially if you also have:

  • Bloody diarrhea
  • Fever
  • Frequent diarrhea
  • Painful bowel movements
  • Rapid heart rate
  • Tenderness when the abdomen is pressed
  • Perforation of the colon
  • Sepsis
  • Shock

You will receive fluids and electrolytes to help prevent dehydration and shock. The process that leads to megacolon can be treated medically first. However, this is usually not enough to reverse the megacolon.

If rapid widening is allowed to continue, an opening (perforation) can form in the colon. Therefore, most cases of toxic megacolon will require surgery, such as colectomy (removal of the entire colon).

You may receive antibiotics to prevent sepsis (a severe infection).


Treatment of the underlying disease, such as ulcerative colitis or Crohn's disease, is important to prevent toxic megacolon.


Stenson WF. Inflammatory bowel disease. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 144.

Peterson, MA. Disorders of the large intestine. In: Marx JA, ed. Rosen's Emergency Medicine: Concepts and Clnical Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier;2009:chap 93.

Marrero F. Severe complications of inflammatory bowel disease. Med Clin North Am. 2008;92:671-686.

Review Date: 1/20/2010
Reviewed By: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; and George F. Longstreth, MD, Department of Gastroenterology, Kaiser Permanente Medical Care Program, San Diego, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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