Chronic inflammation and ulceration of the lining of the colon and rectum, or, especially at the start of the disease, of the rectum alone. The cause of ulcerative colitis is unknown, but the disease is most common in young and middle-aged adults.

Symptoms
The main symptom of ulcerative colitis is bloody diarrhea; the feces may also contain mucus. In severe cases, the diarrhea and bleeding are extensive, and there may be abdominal pain, fever, weight loss, and general malaise. The incidence of attacks varies considerably from person to person. Most commonly, the attacks occur in intervals of a few months. However, in some cases, there may be only a single episode.

Complications
Ulcerative colitis disease may lead to anemia, due to blood loss. Other complications include a toxic form of mega colon (an abnormally enlarged colon), which may become life-threatening; rashes; mouth ulcers; arthritis; conjunctives (inflammation of the membrane covering the eyeball); and uveitis (inflammation of the iris or choroids of the eye). In addition, people whose entire colon has been affected for more than 10 years are at an increased risk of developing cancer of the colon.

Diagnosis
Diagnosis is based on examination of the rectum and the lower colon or of the entire colon, or is made by a barium enema. During sigmoidoscopy or colonoscopy, a biopsy (removal of a tissue sample) may be performed. Samples of feces may be taken for analysis in a laboratory to exclude the possibility of infection by bacteria or parasites. Blood tests may also be necessary.

People who have suffered from ulcerative colitis for a number of years need periodic colonoscopy and biopsy to check for the development of cancer.

Treatment
In most cases, medical treatment effectively controls the disease by relieving symptoms and preventing complications from occurring. For ulcerative colitis occurring in the last part of the colon or rectum, the drugs may be administered as suppositories. If the condition occurs higher up in the intestine, the drugs are taken orally.

Aminosalicylate drugs, such as sulfasalazine (or the newer drugs mesalazine and olsalazine, which have fewer side effects), are used to treat acute attacks and maintain long-term freedom from symptoms. Corticosteroid drugs are given to reduce inflammation during sudden flare-ups. Once the disease is under control, immunosuppressant drugs may be used to prevent relapses.

Colectomy (surgical removal of the colon) may be required for a severe attacks that fails to respond to other treatments, for those with complications such as toxic megacolon, or to avoid colonic cancer in those people who are at high risk. This operation usually produces a dramatic improvement in health, although the person is usually left with an ileostomy (an opening in the surface of the abdomen through which feces are passed).