Ulcerative colitis, also known as colitis or proctitis, is a disease that can cause rectal bleeding, urgency to have a bowel movement, diarrhea, and other problems. It can be difficult to diagnose ulcerative colitis because its symptoms are similar to other intestinal disorders and to another disease called Crohn's disease. Males and females are equally at risk of developing ulcerative colitis, and most people are diagnosed between the ages of 15 and 40. Although doctors are not sure of the cause or causes of this disease, they have theorized that it may be caused by genetic factors, environmental factors, or an overactive immune system. In general, without surgery, ulcerative colitis isn't curable -- so it often requires lifelong treatment.