Purpose: Small renal masses (SRM) can be managed via a variety of nephron-sparing procedures (NSPs), but the association between choice of NSP and renal parenchymal volume (RPV) preservation is not well understood. We sought to examine RPV preservation after partial nephrectomy (PN) performed via open, robotic, or laparoscopic approaches and thermal ablation (TA) performed via cryoablation (CA) or radiofrequency ablation (RFA). Patients and Methods: The study was a retrospective review of three institutional databases of patients with a SRM <4 cm treated via one of the five NSPs (open PN, laparoscopic PN, robotic PN, percutaneous CA, or percutaneous RFA). The 30 most recent consecutive cases treated via each NSP were selected to obtain a total of 150 cases for analysis. Patient characteristics were obtained via manual chart review, and tumor characteristics were assessed via the R.E.N.A.L. nephrometry score. Using three-dimensional rendering software, preoperative and postoperative RPV was calculated for the tumor-bearing kidney, excluding the tumor itself (for preoperative images) or the postsurgical/ablative defect (for postoperative images). The percent change in RPV was compared between the procedure types. Results: One hundred fifty cases were included in the final analysis, with 30 cases from each NSP category. While preoperative tumors were larger in the PN group, there was no difference in the mean nephrometry score between groups. The TA group was found to have a lower mean RPV loss (-8.1% vs -16.5%, p<0.005). There was no difference in the RPV loss between modalities of TA (CA vs RFA) or between approaches to PN (open, laparoscopic, robotic). Matched-pair analysis based on the tumor size and multivariate analysis indicated TA vs PN was independently associated with less RPV loss. Conclusions: TA is associated with less RPV loss than PN in the management of SRM, but there is no difference between modalities of TA (CA vs RFA) or between approaches to PN.
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