Toxic megacolon is a serious condition characterized by swelling and dilation of the large intestine due to inflammation of the intestinal wall and accumulation of excessive amounts of gas. It primarily occurs in association with a severe attack of inflammatory bowel disease—either ulcerative colitis or Crohn’s disease.

Bacterial infections of the colon and certain drugs can also cause toxic megacolon. The disorder produces extreme illness and is life-threatening; treatment requires hospitalization, and surgery may be required to remove the affected portion of the intestine.

The prognosis for toxic megacolon varies; there is a danger of widespread blood poisoning (septic shock), extensive hemorrhaging from the colon, perforation of the colon (peritonitis) and blockage of the arteries that supply blood to the lungs (pulmonary embolism).

What Causes Toxic Megacolon?

  • Ulcerative colitis or Crohn’s disease in the colon are the most common causes of toxic megacolon. In such patients episodes may be triggered by a worsening of the disease, other superimposed diseases resulting in prolonged bed rest, or discontinuing or decreasing prescribed dosages of anti-inflammatories such as sulfasalazine or the 5-aminosalicylic acid (5-ASA) drugs.
  • Some medications—including narcotics (such as morphine and codeine), anticholinergic agents (such as scopolamine and atropine) and some antidepressants—may lead to toxic megacolon.

Symptoms of Toxic Megacolon

  • Acute illness most often preceded by increased intensity of ulcerative colitis or Crohn’s disease symptoms, which include abdominal pain, diarrhea possibly leading to dehydration and blood in the stool.
  • Abdominal distension, pain and tenderness
  • High fever
  • Rapid heart rate
  • Paleness (pallor)
  • Mental changes
  • Shock
  • Absence of bowel sounds

Toxic Megacolon Prevention

  • Do not discontinue medications for ulcerative colitis or Crohn’s disease unless otherwise advised by your doctor.

Toxic Megacolon Diganosis

  • Patient history, especially of prior diagnosis of inflammatory bowel disease
  • Blood tests for anemia and for high white-blood-cell count.
  • Abdominal x-rays
  • Stool cultures to detect an underlying infection.
  • Colonoscopy (insertion of a thin, lighted viewing tube through the anus) may be performed to inspect the colon and rectum. A biopsy of the colon lining may be taken during colonoscopy.
  • Complete blood count

How Toxic Megacolon Is Treated

  • Prompt hospitalization is required. Doctors will attempt to relieve the distended bowel and prevent intestinal perforation (which results in peritonitis) by passing a small tube through the nose or mouth into the intestine to remove gas and fluids.
  • Intravenous solutions and nutrients are given.
  • Blood transfusions are given if necessary.
  • Antibiotics may be prescribed to prevent or treat associated bacterial infection or blood poisoning due to septic shock.
  • Surgery may be required if other treatment fails to relieve the distention and symptoms of toxicity. The affected portion of the large intestine is removed and the remaining sections are sewn together (bowel resection). In some cases it is necessary to create a temporary or permanent colostomy, in which the end of the remaining upper portion of the colon is brought through an opening created in the abdominal wall. Wastes pass through this opening into a bag, instead of being eliminated rectally.

When to Call a Doctor

  • EMERGENCY See a doctor right away for severe abdominal pain and distention with fever.


Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference

Simeon Margolis, M.D., Ph.D., Medical Editor

Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50

Updated by Remedy Health Media

Publication Review By: the Editorial Staff at

Published: 16 Nov 2011

Last Modified: 28 Oct 2014