Ulcerative colitis is a disease that causes inflammation and sores (ulcers) in the lining of the large intestine. It usually affects the lower section (sigmoid colon) and the rectum, but it can affect the entire colon.
Because ulcerative colitis is a chronic condition, symptoms usually develop over time, rather than suddenly. In general, the more of the colon that's affected, the worse the symptoms will be. The main systems are belly pain or cramps, diarrhea and bleeding from the rectum. Experts aren't sure what causes ulcerative colitis, but they think it might be caused by the immune system overreacting to normal bacteria in the digestive tract.
Treatment for depends mainly on how bad the disease is. It usually includes medicines and changes in diet. A few people have symptoms that are long lasting and severe, in some cases requiring medicines or surgery.