What is ulcerative colitis? Ulcerative colitis is an inflammatory disease of the large intestine, or colon. It occurs when inflammation in the colon produces redness, bleeding and pus, which, in turn, causes such symptoms as diarrhea and abdominal pain. Inflammation impairs the ability of the colon to hold its contents, resulting in frequent elimination. Ulcerative colitis is a type of inflammatory bowel disease, along with Crohn’s disease. The exact cause of ulcerative colitis is not known. Ulcerative colitis can affect one side of the colon or the entire colon. Left-side colon involvement is called limited, or distal, colitis. Ulcerative proctitis describes inflammation occurring in the lower part of the colon and rectum. Symptoms range in severity among affected individuals. In a small number of those affected, problems outside of the large intestine may develop, including arthritis, inflammation of the eyes, mouth ulcers, and skin changes. Ulcerative colitis also increases your risk of developing colon cancer. Ulcerative colitis affects teenagers and young adults, with disease onset usually occurring in peaks between ages 15 and 30 years, and less commonly between ages 50 and 70. The condition can run in families, with at least 20% of people affected having a family member with the condition. The prevalence of ulcerative colitis is higher in Caucasians and people with Ashkenazi (Eastern European) Jewish ancestry (Source: NDDIC). Ulcerative colitis itself is not an emergency situation, but serious symptoms may occur. Seek immediate medical care (call 911) for serious symptoms, such as severe abdominal pain, inability to pass gas or stool, and vomiting or vomiting blood. Seek prompt medical care if you are being treated for ulcerative colitis, but mild symptoms recur or persist.