MR imaging of renal masses interpreted on CT to be suspicious

OBJECTIVE. Prior studies have shown that renal MR contrast enhancement impr oves the efficacy of mass and proximal vascular evaluation. This study asse ssed the usefulness of different sequences for characterization of masses t hat appeared suspicious on CT and for prediction of their potential for mal ignancy. SUBJECTS AND METHODS. In a prospective manner 32 patients (age range, 26-78 years; average age, 54 years), each with at least one suspicious mass on C T, were examined with MR imaging. The following sequences were performed: c onventional spin-echo with and without fat saturation, fast spin-echo, and dynamic gadopentetate dimeglumine-enhanced infusion using a 1.5-T supercond ucting magnet. Results were analyzed and compared with pathologic results a fter resection. RESULTS. A total of 65 renal masses of average size 2.6 cm (range, 1-10 cm) were detected with dynamic MR imaging. Seventeen of the 65 masses were mal ignant. Of the 17 malignant masses, three did not enhance on dynamic MR ima ging (because of hemorrhage), Sixteen of the 17 malignant masses were heter ogeneous on T2-weighted images. Three enhancing masses contained fat and al l were angiomyolipomas, Thirty-five of the 65 masses (four with hemorrhage) did not show enhancement, all of which were homogeneous on T2-weighted ima ges and were proven to be cysts. Five masses resulted from infections and h ad heterogeneous T2 appearance. The remaining masses were three hematomas w ith hemorrhage, one column of Bertin, and one aneurysm. CONCLUSION. Renal masses that are interpreted as suspicious on CT may lack MR enhancement because of hemorrhage effects; heterogeneity of their T2 app earance is thus critical in differentiating malignancy from benign disease. Odds-ratio calculations give an adjusted estimate of a 3.36-fold increase (95% confidence interval, 1.8-6.27) in the Likelihood of malignancy when ma sses are heterogeneous on T2-weighted images and a 29-fold increase (95% co nfidence interval, 3.67-241.8) for predicting malignancy when enhancement i s present.