Toxic megacolon

What it is

Toxic megacolon is an outcome of severe colitis rather than a disease of its own. Defined in full, it is a combination of systemic toxicity and non-obstructive colonic dilatation, and it is a potentially fatal complication of inflammatory bowel disease or of infectious colitis, particularly the colitis associated with C. difficile.

What it comes from

Its most common etiologies are inflammatory colitis, that is ulcerative colitis and Crohn's, and bacterial infection with C. difficile, the pseudomembranous colitis. In patients with HIV, CMV colitis is the leading cause of toxic megacolon.

In the comparison of the two inflammatory bowel diseases it sits on the ulcerative colitis side: the complications listed there are hemorrhage and toxic megacolon, while Crohn's disease gives strictures, fistulas, abscess and perianal disease. The point is made again from the other direction: in Crohn disease, bowel strictures are the common long-term complication, and diverticulitis, toxic megacolon, colon cancer and rectal prolapse are less commonly associated with it. And in ulcerative colitis, although blood loss from sustained bleeding may be the most common complication, toxic megacolon must not be missed.

Two more settings are named. In CMV colitis, the acute local complications if left untreated are perforation and toxic megacolon, and the direct agent for treatment is ganciclovir; the other risk factors for CMV colitis given there are long-term steroid therapy and AIDS. In Hirschsprung disease, enterocolitis, with toxic megacolon, is listed as the complication.