Alternative names
Toxic dilation of the colon; Toxic megacolon

Toxic megacolon is a life-threatening complication of other intestinal conditions. It is characterized by a very inflated colon, abdominal distention, and sometimes fever, Abdominal pain, or shock.

Causes, incidence, and risk factors

This is a complication of inflammatory bowel disease, such as ulcerative colitis and Crohn’s disease, and some infections of the colon. Other forms of megacolon exist and can be congenital (present since birth) or associated with some forms of constipation.


  • Abdominal pain  
  • Abdominal distention  
  • Abdominal tenderness  
  • Fever  
  • Rapid heart rate  
  • Dehydration

Signs and tests

There may be signs of septic shock. A physical examination reveals abdominal tenderness and possible loss of bowel sounds.

  • An abdominal film shows colonic dilation.  
  • A CBC may show an elevated white blood cell count.  
  • Blood electrolytes may show a low potassium level or signs of dehydration.


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.

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 (a severe infection).

Expectations (prognosis)

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


  • Sepsis  
  • Shock  
  • Perforation of the colon

Calling your health care provider

Go to the emergency room or call the local emergency number (such as 911) 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.


Treatment of the underlying disease is important in preventing toxic megacolon.

Johns Hopkins patient information

Last revised: December 3, 2012
by Martin A. Harms, M.D.

Medical Encyclopedia

  A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | 0-9

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.