Ulcerative Colitis is an inflammatory bowel disease. Along with Crohn’s disease, they represent the most important conditions. Ulcerative Colitis is a mucosal disease that involves the colon distally and may progressively advance to affect the proximal colon. The disease, if limited to the rectum at the time of diagnosis, is referred to as ulcerative proctitis. The cardinal features are diarrhea and rectal bleeding. The severity of the clinical presentation is often dependent upon the amount of large bowel involved. Approximately one-third of patients have pancolonic involvement at initial presentation. The disease can present as an acute process, a recurrent process, or a chronic ongoing condition. Although mostly seen in the young, it can be seen at any age. The pathologic characteristics of the disease are continuous and concentric superficial involvement of the bowel wall with inflammatory changes, mostly limited to the mucosa. Therefore, unlike Crohn's disease extraluminal inflammatory complications are unusual. In severe fulminant disease, the extent and depth of disease can significantly increase and become transmural, as in the case of toxic colitis. On CT images in longstanding UC, a target appearance of the rectum and/or colon with central low attenuation signifies submucosal fat deposition or edema, often associated with proliferation of the perirectal fat.

Extracolonic manifestations of Ulcerative Colitis include primary sclerosing cholangitis, an ankylosing spondylitis like seronegative spondyloarthropathy; skin changes such as erythema nodosum; and ocular disease such as conjunctivitis, iritis, and episcleritis. Patients with UC are at increased risk for colonic adenocarcinoma.

Multiple CT images obtained after the administration of enteric and intravenous contrast demonstrate circumferential colonic wall thickening beginning in the rectum and extending proximally to the transverse colon, with gradually less severe involvement in the proximal affected portions. Mucosal enhancement is also seen.

Differential considerations include vasculitis resulting in bowel wall edema or hemorrhage; radiation colitis resulting from an obliterative endarteritis; ischemic colitis; and neutropenic colitis. In this patient, there was no history of radiation treatment, neutropenia, atherosclerotic vascular disease, or other signs of vasculitis. A colonoscopy and biopsy was performed and the findings in both were consistent with ulcerative colitis.