Ulcerative colitis involves inflammation of part or all of the large intestine (colon and rectum). Symptoms can include abdominal pain, diarrhea, blood in the stool, fatigue, and weight loss. Ulcerative colitis can be diagnosed with the aid of colonoscopy, imaging studies such as a CT scan, blood tests, and stool studies. A variety of medications can be used to treat the underlying inflammation associated with ulcerative colitis, although surgery is sometimes required.