Ulcerative colitis is an inflammatory bowel disease that causes inflammation and sores, called ulcers, in the lining of the rectum and colon. Ulcers form where inflammation has injured the cells that usually line the colon, which then may bleed and create pus. This inflammation also causes the colon to empty frequently, causing diarrhea.
Colitis can be difficult to diagnose because symptoms such as abdominal pain and diarrhea are so similar to other intestinal disorders. About half the people diagnosed with ulcerative colitis have mild symptoms. Others may suffer frequent fevers, bloody diarrhea, nausea and severe abdominal cramps. It may also cause problems such as arthritis, inflammation of the eye, liver disease and osteoporosis. It is not known why these problems occur outside the colon, but scientists think it may be the result of inflammation triggered by the immune system. Some of these problems go away when the colitis is treated.