Introduction
Inflammatory bowel disease (IBD) is a general term that covers two disorders:
- Ulcerative colitis (UC)
- Crohn's disease (CD)
Some evidence suggests that these two diseases are part of a biologic continuum. At this time, however, they are considered distinct disorders with somewhat different treatment options. The basic distinctions between UC and CD are location and severity. However, as many as 10% of patients with IBD have features and symptoms that match the criteria for both disorders, at least in the early stages. (This is called indeterminate colitis.)
Crohn's disease, also called regional enteritis, is a chronic inflammation of the intestines which is usually found in the terminal portion of the small intestine, the ileum. Ulcerative colitis is a similar inflammation of the colon, or large intestine. These and other IBDs (inflammatory bowel disease) have been linked with an increased risk of colorectal cancer.
Crohn's Disease. Crohn's disease is an inflammation that extends into the deeper layers of the intestinal wall. It is found most often in the area bridging the small and large intestines, specifically in the ileum and the cecum, sometimes referred to as the ileocecal region. Crohn's disease can occur less frequently in other parts of the gastrointestinal tract, including the anus, stomach, esophagus, and even the mouth. It may affect the entire colon or form a string of contiguous ulcers in one part of the colon. It may also develop as multiple scattered clusters of ulcers throughout the gastrointestinal tract, skipping healthy tissue in between.
Click the icon to see an image of Crohn's disease.
Ulcerative Colitis. Ulcerative colitis is an inflammatory disease of the large intestine. Ulcers form in the inner lining, or mucosa, of the colon or rectum, often resulting in diarrhea, blood, and pus. The inflammation is usually most severe in the sigmoid and rectum and typically diminishes higher in the colon. The disease develops uniformly and consistently until, in some people, the colon becomes rigid and foreshortened. [For more information, see In-Depth Report #69: Ulcerative colitis.]
Click the icon to see an image of the structure of the colon.
The Gastrointestinal Tract
The gastrointestinal tract (the digestive system) is a tube that extends from the mouth to the anus. It is a complex organ system that first carries food from the mouth down the esophagus to the stomach and then through the small and large intestine to be excreted out through the rectum and anus.
Esophagus. The esophagus, commonly called the food pipe, is a narrow muscular tube, about 9 1/2 inches long, that begins below the tongue and ends at the stomach.
Stomach. In the stomach, acids and stomach motion break food down into particles small enough so that nutrients can be absorbed by the small intestine.
Small Intestine. The small intestine, despite its name, is the longest part of the gastrointestinal tract and is about 20 feet long. Food that passes from the stomach into the small intestine first passes through three parts:
