Computed tomography (CT) is widely used to assess patients with nonspecific
abdominal pain or who are suspected of having
colitis. The authors recommend multidetector CT with oral, rectal, and intravenous
contrast material and thin sections, which can accurately demonstrate inflammatory changes in the colonic wall and help assess the extent of disease. In most cases, the final diagnosis of the type of
colitis is based on clinical and laboratory data and colonoscopic and biopsy findings, but specific CT features help narrow the differential diagnosis.
Ulcerative colitis is distinguished from
granulomatous colitis (
Crohn disease) in terms of location of involvement, extent and appearance of colonic wall thickening, and type of complications.
Ulcerative colitis and
Crohn disease (
granulomatous colitis) are rarely associated with
ascites, which is often seen in infectious, ischemic, and
pseudomembranous colitis.
Pseudomembranous colitis also demonstrates marked wall thickening and, occasionally, skip areas but is associated with broad-spectrum
antibiotic treatment or
chemotherapy. Neutropenic
colitis is characterized by right-sided colonic and ileal involvement, whereas
ischemic colitis is characterized by vascular distribution pattern and history.
Diverticulitis is a focal asymmetric process with fascial thickening and inflamed
diverticula. Dilatation of a thick-walled appendix with increased enhancement and adjacent stranding suggests
appendicitis, but inflammatory changes may extend to the cecum and terminal ileum. Epiploic appendagitis is a focal rim-enhancing area next to the colon, usually without any substantial colonic wall thickening.