Ulcerative colitis: value of MR imaging

Recent technologic advances have greatly improved the quality of abdominal magnetic resonance imaging (MRI) by allowing the identification of abnormalities in inflammatory bowel disease. Thus far, the role of MRI has been extensively investigated in Crohn disease (CD) and, to a minor extent, in ulcerative colitis (UC), likely due to intrinsic differences between these two diseases. In UC the inflammatory lesions, unlike CD, are confined to the colon, have a predictable spreading, and affect only the inner wall layer; thus endoscopy alone can assess the extent and severity of disease in most cases. However, preliminary studies have demonstrated that MRI also can be a reliable diagnostic tool for UC because it is useful for integrating clinical and endoscopic data. MRI can be valuable in distinguishing CD from UC in uncertain cases by assessing the sparing of the distal ileum and the continuity of colonic involvement. Moreover, MRI can provide important information if endoscopy is incomplete, e.g., due to tight strictures, or contraindicated, e.g., in severely acute disease, due to a high risk of perforation. MRI can detect most of the typical findings of the diseases, such as wall thickening, mural stratification, loss of haustrations, and several complications including fibrotic or neoplastic strictures. In addition, MRI can be extremely valuable in assessing disease activity by monitoring the degree of wall gadolinium enhancement and T2 signal at the level of the affected bowel segments, thus influencing pharmacologic and surgical planning. In the next few years, MRI will likely become the imaging modality of choice in the clinical management of this disease.