Ulcerative colitis is a disease that results in inflammation of the colon. You may be relieved to know that there is no evidence that IBS causes or will turn into colitis. The major difference between ulcerative colitis and IBS is that ulcerative colitis causes visible inflammation and sores along the top lining of the large intestine and rectum, whereas in IBS there is no visible tissue inflammation. Although both disorders can involve diarrhea and abdominal pain, ulcerative colitis can cause blood in the stool and fever, both of which are not symptoms of IBS.

