Ulcerative colitis (UC) involves the colon as a diffuse mucosal disease with distal predominance. The rectum is virtually always involved, and additional portions of colon may be involved extending proximally from the rectum in a continuous pattern. The etiology for UC is unknown. UC is more common in persons of Caucasian race, in women, and in young persons (peak incidence at ages 20 - 25 years).