In vivo factors influencing the freezing cycle during cryoablation of small renal masses

Purpose: The aim of this study is to present a procedural analysis of the cryoablations performed in our department for small renal tumors and to try to identify clinical parameters or factors that influence the freezing rate during the procedure. Patients and Methods: We collected all data from the procedures performed in our department until August 2007. Based on the intraoperative biopsy result, we grouped the cases in two groups: renal-cell carcinoma (RCC) and benign. We calculated the freezing rate in both groups and compared them. Finally, we performed a univariate and multivariate analysis to identify clinical parameters that significantly influence the freezing rate. Results: A total of 70 cryoablations of small renal tumors in 67 patients were performed during this period. From these, 56 procedures met the inclusion criteria and were analyzed further. The RCC group consisted of 48 cases (39 RCC and 9 lesions with a nondiagnostic biopsy) while 8 formed the benign group. There was no difference in the freezing rate between these two groups. Preoperative creatinine levels above 120¿IU, diabetes mellitus, American Society of Anesthesiologists score 3, and location of the tumor at the lower pole were found to increase the freezing rate. The only factor that significantly decreased the freezing rate was the presence of chronic obstructive pulmonary disease. The multivariate analysis showed that the location of the tumor and diabetes mellitus influence more significantly the temperature v time graph. Conclusions: The freezing rate during cryotherapy of small renal tumors is significantly influenced by various clinical factors, while there are no differences in the freezing rate of those proven small malignant tumors and the small benign lesions.