Ulcerative colitis (Colitis ulcerosa, UC) is a form of inflammatory bowel disease (IBD) that causes inflammation and ulcers in the colon.The disease is a type of colitis, which is a group of diseases that cause inflammation of the colon, the largest section of the large intestine, either in segments or completely.lthough the symptoms of ulcerative colitis can sometimes diminish on their own, the disease usually requires treatment to go into remission. Ulcerative colitis has an incidence of 1 to 20 cases per 100,000 individuals per year, and a prevalence of 8 to 246 per 100,000 individuals.