Magnetic resonance in the staging of renal carcinoma. The results compared with computed tomography in 42 cases

In order to investigate the value of MRI in the staging of renal cell carcinoma and to compare the results of MRI and CT, the authors evaluated by means of MRI and CT 42 patients affected with renal cell carcinoma. All patients underwent surgery, and pathology of the surgical specimens was performed. A comparison was made between the surgical and pathologic data and MRI and CT results. Moreover, a comparative evaluation of MRI and CT findings was also made. From the comparison between pathologic data and CT and MRI results MRI was seen to have correctly staged 36 of 42 cases (85%), versus CT 33 of 42 cases (78%). Moreover, MRI proved to be superior to CT in evaluating venous involvement (stages III A and III C) and extra-fascial tumor spread (stage IVA). On the contrary, no significant differences were found between MRI and CT in the evaluation of perirenal involvement (stages I-II) and lymph node metastases (stage III B). MRI misdiagnosed 6 of 42 cases: 2 false negatives in evaluating extracapsular tumor spread, 1 false positive of mesenteric infiltration, 1 false positive of renal vein thrombosis, 1 false positive and 1 false negative in evaluating lymph node metastases. CT misdiagnoses (9 of 42 cases) were the same as those of MRI in 5 cases, while in the MRI false positive of renal vein thrombosis CT was correct. The extant 4 incorrect CT findings were: 2 false positive of renal vein thrombosis, 1 false negative of infiltration of diaphragm and psoas muscle, 1 false positive infiltration of the right liver lobe. As yet, therefore, MRI cannot be routinely employed to stage all renal cancer patients. On the contrary, MRI should be considered as a second-choice diagnostic tool to employ in selected cases when CT alone cannot solve all the problems relative to staging.