Membrane anatomy-guided robot-assisted partial nephrectomy: operational definition and association with warm ischemia time in a single-surgeon cohort

Background A standardized anatomical framework for robot-assisted partial nephrectomy (RAPN) is lacking. This study evaluates a stepwise membrane anatomy-guided pathway and its association with warm ischemia time (WIT) and clamping-phase efficiency, controlling for surgical experience and temporal confounding. Methods We evaluated 151 consecutive RAPN cases (30 conventional vs. 121 membrane anatomy-guided) performed by a single-center, single-surgeon cohort using the da Vinci Xi System (2022–2025). Multivariable linear regression with HC3 robust standard errors was performed to assess the primary outcome (WIT), adjusting for clinical covariates and nonlinear cumulative case sequence (natural cubic spline, df = 3). Chronology-adjusted sensitivity analyses and propensity-score overlap weighting were conducted. Results Despite substantial chronological overlap between pathways, the membrane-guided pathway was independently associated with a 4.05-min reduction in mean WIT (95% CI -6.82 to -1.28; P = 0.004) without compromising surgical margin safety. This effect was consistent across linear, calendar-time, propensity-weighted, and overlap-cohort sensitivity analyses (-3.67 to -4.19 min; all P < 0.05). The membrane-guided approach also significantly increased the odds of WIT ≤ 25 min (adjusted OR 5.25; P = 0.003) and modified Trifecta achievement (adjusted OR 4.97; P = 0.005). Conclusion The membrane anatomy-guided pathway consistently improves clamping-phase efficiency and shortens WIT in RAPN after accounting for learning curves and temporal trends. Given the retrospective design, these findings reflect associative rather than definitive causal effects.