MR Findings of Bowel Ischemia with Mesenteric Vascular Occlusion: Comparison with Pathologic Findings in a Cat Model

ABSTRACT

PURPOSE: In order to determine the characteristic MR findings for the early diagnosis of bowel ischemia, we analysed the dynamic enhanced MR images of ischemic bowel induced by mesenteric vascular occlusion in a cat model, and compared the T1-and T2- weighted images (WI) of extracted bowel with the pathologic findings. MATERIALS AND METHODS: According to the ischemic period, twelve cats were assigned to either the normal control group (no ischemic period, n=2), the acute ischemic group (ligation of mesenteric vessels for 3 hours, n=6) or the subacute ischemic group (ligation of mesenteric vessels for 10 hours, n=4). Under general anes-thesia,laparotomy was performed. The ileal artery and vein were ligated, and a columnar surface coil was ap-plied to the expected bowel ischemia. Using a 4.7 T MR scanner, contrast-enhanced T1WI were obtained, after bolus injection of contrast media, at 10, 20, 30, 60, and 90minutes. After formalin fixation of the extracted bowel, T1- and T2WI were obtained, and the specimens were pathologically examined. MR signal intensity at each layer of the bowel wall was measured and compared with the histopathologic findings. RESULTS: On contrast enhanced MR images, the submucosal layer showed most intensive enhancement, fol-lowed-in decreasing order of signal intensity- by muscle and mucosa. Time to peak enhancement of bowel wall was 10-minutes in the normal control group, and 20 and 60minutes in the acute and subacute bowel is-chemia groups, respectively. On T1WI, no significant differences in signal intensity were observed between the ischemic group and the normal control group. On T2WI, the signal intensity of the submucosal layer of the acute ischemic group was significantly higher than that of the normal control or subacute ischemic group, and the signal intensity of the muscular layer of the ischemic group was significantly higher than that of the normal control group. CONCLUSION: Time to peak enhancement of bowel wall was a helpful criterion for assessment of the ischemic period. Analysis of the signal intensity of the bowel wall layer was useful for the early detection of bowel ischemia.