On-clamp versus purely off-clamp robot-assisted partial nephrectomy in solitary kidneys: comparison of perioperative outcomes and chronic kidney disease progression at two high-volume centers

BACKGROUND: Minimal literature describes the impact of hilar control on the progression to chronic kidney disease (pCKD) after robotic partial nephrectomy (RPN) in solitary kidneys (SK). The aim of this study was to compare purely off-clamp (ocRPN) vs. on-clamp robotic partial nephrectomy (onRPN) in SK and to identify predictors of pCKD at two high-volume centers. METHODS: Between December 2013 and October 2019, 54 patients with SK underwent ocRPN and onRPN for renal tumors at two institutions. Baseline and perioperative data were analyzed. Newly onset of CKD stage 3b,4,5 (CKD3b,4,5) was assessed by Kaplan-Meier curves and compared for warm ischemia time (WIT) with the log-rank test. Cox regression analysis was used to identify predictors of pCKD. RESULTS: At a median follow-up of 13 months (IQR 6.3-34), newly onset of CKD3b and CKD 4.5 were observed in 11.1% and 7.4% of patients, respectively. onRPN was associated with a higher risk of progression to CKD 3b,4,5 stages (P=0.034) and higher rate of perioperative complications (P=0.03). On univariable analysis eGFR at discharge (eGFRd), positive surgical margins status (PSM) and WIT were predictors of newly onset of CKD3b,4,5 (each P<0.05). Multivariable analysis identified eGFRd (HR 0.88; CI 95% 0.81-0.96) and WIT (HR 1.09; CI 95% 1.02-1.16) as independent predictors of pCKD (each P<0.01). Main limitations include the retrospective nature of the study, the short-term follow-up and the lack of data adjustment for parenchymal volume loss. CONCLUSIONS: eGFRd and WIT during RPN are independent predictors of pCKD in SK. In this setting a critical reduction of WIT should be achieved according to the oncologic outcome. In patients with SK, WIT represents the only surgical modifiable factor of RPN for avoiding a quicker onset of pCKD.