Toxic megacolon

Toxic megacolon is a complication that can be seen in both types of inflammatory bowel disease, and less commonly in infectious colitis, as well as in some other types of colitis.

Toxic colitis is preferred by many now as the colon is not always dilated. 

The mechanisms involved in the development of toxic megacolon are not entirely clear, although chemical mediators such as nitric oxide and interleukins are thought to play a pivotal role in its pathogenesis 5.

The colon (typically transverse colon) becomes dilated to at least 6 cm. There is an additional loss of haustral markings, with pseudopolyps often extending into the lumen. Thumbprinting from mucosal oedema may be present. There may be signs of pneumoperitoneum if dilatation has progressed to cause perforation.

  • barium studies and colonoscopy should be avoided, due to the risk of perforation
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Article information

rID: 24380
Synonyms or Alternate Spellings:
  • Toxic megacolon (TM)
  • Megacolon toxicum
  • Toxic colitis

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Cases and figures

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    Case 1: with underlying C. difficile colitis
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    Case 2
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