A comparison of outcomes between transperitoneal and retroperitoneal robotic assisted partial nephrectomy in patients with completely endophytic kidney tumors

Introduction: Retroperitoneal robotic partial nephrectomy (RPN) has been shown to have comparable outcomes to the transperitoneal approach for renal tumors. However, this may not be true for completely endophytic tumors as they pose significant challenges in RPN with increased complication rates. Hence, we sought to compare the safety and feasibility of retroperitoneal RPN to transperitoneal RPN for completely endophytic tumors. Methods: We performed a retrospective analysis of patients who underwent RPN for a completely endophytic renal mass using either transperitoneal or retroperitoneal approach from our multi-institutional database (n = 177). Patients who had a solitary kidney, prior ipsilateral surgery, multiple/bilateral tumors, and horseshoe kidneys were excluded from the analysis. Overall, 156 patients were evaluated (112 [71.8%] transperitoneal, 44 [28.2%] retroperitoneal). Baseline characteristics, perioperative and postoperative data were compared between the surgical transperitoneal and retroperitoneal approach using Chi-square test, Fishers exact test, t test, Mood median test and Mann Whitney U test. Results: Of the 156 patients in this study, 86 (56.9%) were male and the mean (SD) age was 58 (13) years. Baseline characteristics were comparable between the 2 approaches. Compared to transperitoneal approach, retroperitoneal approach had similar ischemia time (19.6 [SD = 7.6] minutes vs. 19.5 [SD = 10.2] minutes, P = 0.952), operative time (157.5 [SD = 44.8] minutes vs. 160.2 [SD = 47.3] minutes, P = 0.746), median estimated blood loss (50 ml [IQR: 50, 150] vs. 100 ml [IQR: 50, 200], P = 0.313), median length of stay (1 [IQR: 1, 2] day vs. 1 [IQR: 1, 2] day, P = 0.126) and major complication rate (2 [4.6%] vs. 3 [2.7%], P = 0.621). No difference was observed in positive surgical margin rate (P = 0.1.00), delta eGFR (P = 0.797) and de novo chronic kidney disease occurrence (P = 1.000). Conclusion: Retroperitoneal and transperitoneal RPN yielded similar perioperative and functional outcomes in patients with completely endophytic tumors. In well-selected patients with purely endophytic tumors, either a retroperitoneal or transperitoneal approach could be considered without compromising perioperative and postoperative outcomes.