Ulcerative colitis is categorized according to location:
Proctitis involves only the rectum
Proctosigmoiditis affects the rectum and sigmoid colon
Left-sided colitis encompasses the entire left side of the large intestine
Pancolitis inflames the entire colon
George F. Longstreth, MD, Department of Gastroenterology, Kaiser Permanente Medical Care Program, San Diego, California. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, and Stephanie Slon.