DUAL-PHASE HELICAL CT OF THE KIDNEY - VALUE OF THE CORTICOMEDULLARY AND NEPHROGRAPHIC PHASE FOR EVALUATION OF RENAL LESIONS AND PREOPERATIVE STAGING OF RENAL-CELL CARCINOMA

OBJECTIVE. Our objective was to evaluate early-phase unenhanced and la te-phase contrast-enhanced helical CT in revealing renal lesions and s taging renal cell carcinomas. SUBJECTS AND METHODS. Contrast-enhanced helical CT of the kidneys was performed in 145 patients who also under went unenhanced CT. Contrast-enhanced CT was performed in the corticom edullary phase (CMP) and nephrographic phase (NP). A total of 173 lesi ons in 96 patients were proven histologically or cytologically. The pe rformance of helical CT in the three study groups was compared: unenha nced and CMP enhancement, group 1; unenhanced and NP enhancement, grou p 2; unenhanced, CMP enhancement, and NP enhancement, group 3. Among t he parameters evaluated were the sensitivity for helical CT of all 173 renal lesions and the sensitivity and specificity for the 90 malignan t rumors. Also, the preoperative CT staging of the 76 renal cell carci nomas was correlated with the pathologic specimens. RESULTS, The sensi tivity for detection of all renal lesions in group 1 (84%) was signifi cantly less than in groups 2 and 3 (97% and 100%). The specificity and accuracy of helical CT in revealing renal cell carcinomas were signif icantly higher (p <.05) in group 3 (95% and 95%, respectively) than in groups 1 (93% and 92%, respectively) and 2 (89% and 91%, respectively ). Two renal cell carcinomas were overlooked by the interpreters of th e helical scans in group 1. The accuracy of preoperative CT staging of renal cell carcinomas was significantly better (p <.05) in group 3 (9 1%) than in groups 1 (82%) and 2 (86%). CONCLUSION. When patients unde rwent unenhanced helical CT, CMP helical CT, and NP helical CT, we ach ieved a better rate of detection and characterization of renal lesions and better preoperative staging of renal cell carcinomas than when we used either CMP helical CT or NP helical CT alone.