Ulcerative colitis is a disease that causes inflammation and ulcers (sores) in the lining of the large intestine. It’s also called inflammatory bowel disease (IBD), the general name for diseases that cause inflammation in the intestinal tract.
Ulcers form where inflammation has killed the cells that usually line the colon, then bleed and produce pus. Inflammation in the colon also causes the colon to empty frequently, resulting in diarrhea.