Toxic megacolon is more likely to occur with ulcerative colitis, but it can also develop in Crohn's disease. Unfortunately, medications used for pain and diarrhea, such as opiates, and drugs that reduce spasms of the colon may increase the risk of toxic megacolon, although its incidence is decreasing as more effective treatments are developed. The deep ulcers of Crohn's disease frequently result in the development of fistulas, channels that can burrow between organs, loops of the intestine, or between the intestines and skin. If fistulas develop between the loops of the small and large intestines, they can interfere with absorption of nutrients. They often form pockets of infection or abscesses, which may become life threatening without treatment.
Fistulas are rare in ulcerative colitis.
Intestinal Blockage Inflammation from Crohn's disease produces segments of scar tissue known as strictures that can constrict the passages of the intestines, causing bowel obstruction with severe cramps and vomiting. Strictures usually occur in the small intestine but can also occur in the large intestine. Cancer Chronic ulcerative colitis increases the risk for colon cancer. Individuals should discuss with their physician the risks and benefits of these screening procedures. Patients with Crohn's disease of the colon have a similar risk for colon cancers.