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

Our objective was to evaluate early-phase unenhanced and late-phase contrast-enhanced helical CT in revealing renal lesions and staging renal cell carcinomas. Contrast-enhanced helical CT of the kidneys was performed in 145 patients who also underwent unenhanced CT. Contrast-enhanced CT was performed in the corticomedullary phase (CMP) and nephrographic phase (NP). A total of 173 lesions in 96 patients were proven histologically or cytologically. The performance of helical CT in the three study groups was compared: unenhanced and CMP enhancement, group 1; unenhanced and NP enhancement, group 2; unenhanced, CMP enhancement, and NP enhancement, group 3. Among the parameters evaluated were the sensitivity for helical CT of all 173 renal lesions and the sensitivity and specificity for the 90 malignant tumors. Also, the preoperative CT staging of the 76 renal cell carcinomas was correlated with the pathologic specimens. The sensitivity for detection of all renal lesions in group 1 (84%) was significantly less than in groups 2 and 3 (97% and 100%). The specificity and accuracy of helical CT in revealing renal cell carcinomas were significantly 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 the helical scans in group 1. The accuracy of preoperative CT staging of renal cell carcinomas was significantly better (p < .05) in group 3 (91%) than in groups 1 (82%) and 2 (86%). When patients underwent unenhanced helical CT, CMP helical CT, and NP helical CT, we achieved 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.