Ulcerative colitis.

Severe disease — Patients with severe ulcerative colitis usually have a large region of the colon involved, often the entire colon. Symptoms of severe ulcerative colitis include Diagram of the colon and rectum Ulcerative Colitis (UC) is a disease in which the lining of the colon (the large intestine) becomes inflamed. The immune system mistakenly targets the lining of the colon, causing inflammation, ulceration, bleeding and diarrhea. The inflammation almost always affects the rectum and lower part of the colon, but it can also effect the entire colon