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. Other cancers, such as lymphoma or carcinoma of the small intestine or anus, may also be more common in patients with Crohn's disease, but the risk is not high. Complications Occurring Outside the Gastrointestinal Tract Inflammation may occur in tissues beyond the gastrointestinal tract, most commonly in the joints, which can cause stiffness and arthritic-like symptoms.