Toxic Megacolon

Reviewed by: HU Medical Review Board | Last Reviewed: January 2018.

Toxic megacolon is a severe, life-threatening complication of Crohn’s disease and ulcerative colitis, the two major forms of inflammatory bowel disease (IBD).1 When toxic megacolon occurs, the large intestine (colon) begins to widen (dilate). Other terms for toxic megacolon are “toxic colitis” or “fulminant colitis.”2

It is not clear exactly what causes toxic megacolon. It may be due to problems with muscle contraction or digestive reflexes.1 Some triggers for this complication are:1

  • Stopping certain medications abruptly (corticosteroids or anti-inflammatories)
  • Taking certain medications (narcotics, anticholinergics, or chemotherapy)
  • Having a colonoscopy
  • Having a barium enema. (In this procedure, a liquid contrast material is injected into the large intestine via the rectum before having an x-ray.)

Toxic megacolon is a relatively rare complication.3 Among people with IBD, toxic megacolon occurs more often in people with ulcerative colitis than Crohn's disease.1 Although it occurs in about 2.5% of all those with ulcerative colitis, the incidence increases from 6% to 17% among those with ulcerative colitis who are hospitalized.Among people with Crohn’s disease who develop toxic megacolon, it is more likely among those with inflammation in the ileum and colon.4 In a study of people who needed surgery for Crohn’s disease, toxic megacolon was the cause for almost one-quarter of operations.4

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What are symptoms of toxic megacolon?

Symptoms of toxic megacolon include:2,5

  • Frequent bloody diarrhea
  • Abdominal pain, swelling/stretching, and tenderness
  • Fever
  • Rapid heart beat
  • Low blood pressure
  • Decreased urine output

If you have symptoms of toxic megacolon, seek medical care right away. Toxic megacolon can be life threatening.5

What other conditions can cause toxic megacolon?

Toxic megacolon is actually more common in people with ulcerative colitis than people with Crohn’s disease.2 Bacterial or viral infections can also cause toxic megacolon.4 The bacteria C. difficile is an increasingly common cause of toxic megacolon.

How is toxic megacolon evaluated?

Your health care provider will do blood tests to check for:1,2

  • Inflammation
  • Infection
  • Too much acid in the blood
  • Anemia

Your provider will also x-ray your colon. The x-rays let your provider see if your colon has gotten wider or has ulcers. These are signs of toxic megacolon.1 Computed tomography (CT) scan or ultrasound are alternatives to x-ray.4

How is toxic megacolon treated?

You will be treated with intravenous (IV) fluids to prevent shock and dehydration.5 You may also be given antibiotics.1 You may be told not to eat or drink anything, which is called bowel rest. If you are on bowel rest, you may be given IV nutrition (also called parenteral nutrition or TPN).1 A tube may be inserted through your nose into your large intestine to suction out air and waste.3

If toxic megacolon does not improve quickly, you might need surgery.1 Surgery is always done if you have a hole (perforation) in the colon. Other reasons for surgery are continued widening (dilation) and uncontrollable bleeding. The surgeon may need to remove the entire colon, also known as a total colectomy.5

What are complications of toxic megacolon?

The complications of toxic megacolon can be serious. In particular, a hole (perforation) could develop in your colon.1 A perforation allows the contents of your intestine to leak into the abdominal cavity.6 This can lead to a serious abdominal infection or body-wide infection.

Without treatment, a perforation can be deadly. A perforation is treated with surgery to repair the hole.6 The surgeon may also create a temporary ostomy, attaching the end of the ileum or large intestine to a small opening in the skin. Waste is eliminated through the small opening.