Arterioportal shunts in cirrhotic patients: evaluation of the difference between tumorous and nontumorous arterioportal shunts on MR imaging with superparamagnetic iron oxide.

OBJECTIVE: The study objective was to distinguish between the features of tumorous and nontumorous arterioportal shunts on superparamagnetic iron oxide-enhanced MR imaging in patients with cirrhosis.

SUBJECTS AND METHODS: Ten arterioportal shunts in eight patients, including four tumorous and six nontumorous arterioportal shunts, were evaluated on T2-weighted turbo spin-echo and T2(*)-weighted gradient-echo sequences before and after administration of superparamagnetic iron oxide. Qualitatively, the relative signal intensity of the arterioportal shunt compared with that of the surrounding liver parenchyma was categorized into three grades: high, slightly high, and not detected. Quantitatively, signal-to-noise ratio, contrast-to-noise ratio, lesion-to-liver contrast, and percentage enhancement were calculated and compared between tumorous and nontumorous arterioportal shunts by a nonparametric statistical test (Mann-Whitney test).

RESULTS: Qualitatively, all four tumorous arterioportal shunts appeared as areas of slightly high or high intensity without and with superparamagnetic iron oxide on T2-weighted turbo spin-echo images and changed from isointensity to high intensity after the administration of superparamagnetic iron oxide on T2(*)-weighted gradient-echo images. All nontumorous arterioportal shunts except one could not be recognized without or with superparamagnetic iron oxide on either sequence. Quantitatively, with superparamagnetic iron oxide the contrast-to-noise ratio and the lesion-to-liver contrast of the tumorous arterioportal shunts were significantly higher than those of the nontumorous arterioportal shunts.

CONCLUSION: Tumorous arterioportal shunts are seen as areas of reduced signal loss, whereas most nontumorous arterioportal shunts are seen as areas of normal signal loss, like the normal liver parenchyma. The difference is more marked on T2(*)-weighted gradient-echo images than on T2-weighted turbo spin-echo images.