R.E.N.A.L. nephrometry score accurately predicts complications following laparoscopic renal cryoablation

Purpose: The R.E.N.A.L. nephrometry is a standardized scoring system that quantifies the complexity of kidney tumors. We evaluated our experience with laparoscopic cryoablation and determined the ability of nephrometry to predict complications. Materials and Methods: We reviewed the records of all patients who underwent laparoscopic cryoablation from July 2005 to February 2010 at 3 institutions. The composite R.E.N.A.L. score was determined using preoperative imaging, and tumors were categorized as low (4-6), moderate (7-9) or high complexity (10-12). Perioperative data were analyzed to determine the presence of complications. The distribution of surgical complications and tumor categories was compared using the chi-square and Student's t test. Logistic regression was used to analyze the association between nephrometry score and postoperative complications. Results: A total of 210 patients underwent laparoscopic cryoablation, 77 of whom had available preoperative imaging. Mean patient age was 64.5 years and mean tumor size was 2.6 cm (range 1 to 4.5). Mean nephrometry score was 6.1 (range 4 to 12). Of the tumors 47 (61%) were categorized as low, 23 (30%) as moderate and 7 (9%) as high complexity lesions. Overall there were 15 (19.5%) complications, including 7 (9.5%) major and 8 (10%) minor complications. There was a significant difference in complication rates among the low (47 patients, 0%), moderate (23 patients, 35%) and high complexity (7 patients, 100%) groups, respectively (p <0.001). On multivariate analysis nephrometry score was independently associated with a higher risk of postoperative complications (OR 2.23, 95% CI 1.05-2.11, p = 0.008). Conclusions: In a multi-institutional cohort of patients undergoing laparoscopic cryoablation, the R.E.N.A.L. nephrometry score is independently associated with the occurrence of complications. Therefore, nephrometry can be used to successfully stratify patients in terms of anticipated risk of complications which, in turn, may help with surgical decision making.