In inflammatory bowel diseases, the intestine (bowel) becomes inflamed, often causing recurring abdominal cramps and diarrhea.

The two primary types of inflammatory bowel disease are Crohn's disease and ulcerative colitis. These two diseases have many similarities and sometimes are difficult to distinguish from each other. However, there are several differences. For example, Crohn's disease can affect almost any part of the digestive tract, whereas ulcerative colitis almost always affects only the large intestine. The cause of these diseases is not known but may involve an overactive immune reaction to intestinal bacteria or other agents in people with a genetic predisposition. More recently recognized inflammatory bowel diseases include collagenous colitis, lymphocytic colitis, and diversion colitis.

To make a diagnosis of inflammatory bowel disease, a doctor must first exclude other possible causes of inflammation. For example, infection with parasites or bacteria may cause inflammation. Therefore, the doctor performs several tests. Stool samples are analyzed for evidence of a bacterial or parasitic infection (acquired during travel, for example), including a type of bacterial infection (Clostridium difficileinfection) that can result from antibiotic use (see Clostridium difficile-Induced Colitis). A doctor also checks for sexually transmitted diseases of the rectum, such as gonorrhea, herpesvirus infection, and chlamydial infection. Tissue samples (biopsies) may be taken from the lining of the rectum during a sigmoidoscopy (an examination of the sigmoid colon using a viewing tube) and examined microscopically for evidence of other causes of colon inflammation (colitis). Other possible causes of similar abdominal symptoms that a doctor tries to exclude are ischemic colitis, which occurs more often in people older than 50; certain gynecologic disorders in women; celiac disease; and irritable bowel syndrome.

Last full review/revision August 2006 by David B. Sachar, MD; Aaron E. Walfish, MD