Ulcerative colitis is part of a group of conditions called inflammatory bowel diseases (IBD). Another disease in this group is Crohn's disease. It is important to note that inflammatory bowel disease is NOT the same as irritable bowel syndrome (IBS).
It is still unclear what causes this condition. It is thought to be a combination of genetic and environmental factors, probably set off by a trigger of some kind. The mechanism if the disease is that the immune system recognizes the lining of the colon as foreign and attacks it, leading to inflammation. This inflammation causes the lining of the colon to develop ulcers and bleed.
The most common symptoms of mild ulcerative colitis include:
In people with moderate to severe disease, the following symptoms can develop:
People with ulcerative colitis can develop inflammation outside of the colon. Inflammation often affects large joints (hips, knees), causing swelling and pain, as well as the eyes, the skin, and, less commonly, the lungs. These symptoms usually occur when ulcerative colitis symptoms are active (during a flare). However, inflammation can develop even when symptoms are quiet (in remission).
Ulcerative colitis is usually diagnosed based upon your symptoms, a physical examination, and laboratory tests. You will probably need a colonoscopy. These tests allow your doctor to take tissue samples from the colon, which can confirm ulcerative colitis and rule out other conditions that have similar symptoms, including Crohn’s disease, diverticulitis, and certain infections.