MR imaging of ulcerative colitis.

High-resolution magnetic resonance imaging (MRI) was used to study 16 resected rectosigmoid specimens of patients treated with total colectomy for severe ulcerative colitis (UC). Six normal colon specimens were also studied as a control group. Moreover, a parallel study of the pelvis of 24 patients with a proven diagnosis of UC was performed with the same MR system. Both in vitro and in vivo MRI findings [thickening and signal intensity (SI)] of the mural layers were qualitatively evaluated by two radiologists and compared with gross and microscopic aspects. In vitro results showed that MRI was able to identify all layers of the colonic wall. In particular in UC specimens, MRI identified thickening and the peculiar abnormal hyperintensity of the mucosal and submucosal layers on spin-echo (SE) T1-weighted images. In vivo results confirmed the high-signal intensity of the mucosal and submucosal layers. These findings were not observed in the control group in which the superficial layers appeared low in intensity on SE T1 images. Our preliminary experience suggests that MRI should be considered a new imaging modality for detecting UC colonic wall changes.