RENAL MASSES - ASSESSMENT OF CORTICOMEDULLARY-PHASE AND NEPHROGRAPHIC-PHASE CT SCANS

PURPOSE: To evaluate the role of thin-section helical computed tomogra phy (CT) performed during the corticomedullary phase (CMP) and nephrog raphic phase (NP) of contrast enhancement in the detection and charact erization of renal masses. MATERIALS AND METHODS: Renal CT scans and m edical records of 33 patients were retrospectively reviewed. In all ex aminations, 5-mm-thick, contiguous, helical-mode scans were obtained b efore and 40 seconds after initiation of dynamic bolus injection of co ntrast material (CMP images); 5-mm-thick, contiguous, axial-mode scans were obtained after completion of CMP scanning (NP images). RESULTS: At review of CMP, NP, and combination images, 259, 389, and 417 lesion s, respectively, were identified. The greatest difference in detection occurred in the renal medulla, with 25 lesions identified on CMP imag es and 111 lesions identified on NP images. False-positive results occ urred when CMP images were reviewed without NP images. CONCLUSION: CT scans obtained only during the CMP of contrast enhancement fail to dep ict many renal masses that are easily seen on NP images.