© Turkish Society of Radiology 2010

U lcerative colitis is a chronic disease characterized by diffuse mu-cosal inflammation that is localized to the colon. In approxi-mately 95 % of cases, ulcerative colitis involves the rectum and may extend proximally in a symmetrical, circumferential, and uninter-rupted pattern to involve part or all of the large intestine. Ulcerative colitis is usually associated with recurrent attacks, with complete remis-sion of symptoms in the interim (1–4). Disease activity indices are prediction rules that are used to objec-tively measure the activity of disease, to judge patients ’ responses to treatment in clinical trials and to choose which drug and dose to administer. Disease activity can be assessed clinically and endoscopi-cally. Because the rectum is invariably involved in ulcerative colitis, flexible rectosigmoidoscopy is sufficient for depicting disease activity (1, 3). Despite its use as a gold standard, endoscopy is an invasive technique and has limitations. Due to the presence of severe inflam-mation in the colon, the use of colonoscopy in patients with active ulcerative colitis carries a high risk of perforation of the tissue. In ad