Ulcerative colitis is one of two forms of inflammatory bowel disease (IBD), the other form being Crohn's disease. Unfortunately, the cause of this form of IBD remains unknown, but diagnosis is still possible through excluding other possible conditions and by a full review of the symptoms. Ulcerative colitis is a condition in which the moist tissue layer that lines the colon and rectum, called the mucosa, has become inflamed.

Even though we don't know the exact causes of ulcerative colitis, there are some good theories involving the role of the immune system and/or infections.(1) The infectious theory assumes that the body is reacting normally to an as-of-yet unrecognized pathogen. The immunologic theory, on the other hand, proposes that the immune system is responding inappropriately to a substance which is causing the body to create antibodies. Sometimes these substances, called antigens, are thought to create an autoimmune reaction, or a reaction in which the immune system acts in response to things which are normal to most people.(2) Some of the microorganisms suspected of being involved in the IBD include viruses, protozoans, micoplasmas, and other bacteria.

Ulcerative colitis is confined to the rectum and colon, and affects the mucosa. In some instances, a short segment of the lower section of the small intestine called the terminal ileum may also be inflamed. This condition is referred to as backwash ileitis. Unlike Crohn's disease, the deeper longitudinal muscular layers, and regional lymph nodes are usually not involved.(3) Since the inflammation is usually confined to the mucosa and submucosa, tears and obstruction are uncommon. However, depending on how much damage has been done to the mucosa, there may be diarrhea and possibly some bleeding.

The complications of ulcerative colitis may range from mild to even life threatening. Some of the complications seen most frequently in individuals with this condition include hemorrhoids, anal fissures or slits, or abscesses in or around the rectum. These complications are most likely to occur during active colitis episodes. A major complication that may occur in a small number of people with ulcerative colitis or Crohn's disease is called toxic megacolon. In this condition, the patient usually has a high fever, swollen or distended abdomen, elevated white count, and a dilated colon that can be observed on an x-ray. There are other very serious complications that may also occur, but these occur infrequently. It is important to realize that the risk of colon cancer increases in patients with ulcerative colitis when compared to the normal population.

The inflammatory condition that occurs with ulcerative colitis has been blamed for other complications as well. Complications that lie outside of the colon are called systemic complications. Approximately 11% of patients with ulcerative colitis have been reported to have complications involving the liver.(4) These would involve such complications as fatty liver, chronic active hepatitis, and cirrhosis.

Other systemic complications that occur include joint complications in the form of arthritis. This form of arthritis does not deform or destroy the joints. The joints most commonly affected are the knees, hips, ankles, wrists, and elbows, and severity is usually associated with the severity of the ulcerative colitis. Complications of the eyes may occur in up to 10% of patients with IBD. Finally, several studies report that 5 to 10 percent of patients with ulcerative colitis may have complications involving their skin. (5)