An evaluation of the effectiveness of CT vs. other imaging modalities in the diagnosis of atypical renal masses.

A retrospective review of 34 patients undergoing nephrectomy for suspected renal malignancy was undertaken to evaluate the effectiveness of computed tomography (CT), ultrasound, arteriography, and cyst puncture in providing a definitive preoperative diagnosis of benign vs. malignant renal abnormality. The predictive value of a test suggesting malignancy was 88% for angiography, 86% for ultrasound, 71% for cyst puncture, and 80% for CT. The predictive value of a test suggesting no malignancy for non-CT imaging modalities was poor. The predictive value of renal CT increased to 96%, when three or more characteristics are present which suggest the lesion is not a simple, benign renal cyst. Using these criteria all malignancies were identified, and all but one benign lesion excluded. Unusual lesions that have equivocal or indeterminate diagnostic studies and only one or two noncystic CT features should undergo selective exploration rather than radical nephrectomy.