Objectives: To assess the incidence of postoperative arterial malformation (AM) and urine leak/urinoma (UL) after robotic partial nephrectomy (RPN) in a contemporary series and to evaluate risk factors for these complications. Materials and Methods: All RPNs were queried from Institutional Review Board-approved retrospective and prospective nephrectomy databases. Demographics, perioperative variables, and postoperative complications were collected. Differences between cohorts were analyzed using univariate analysis. Postoperative complications were graded using the Clavien-Dindo system. UL was defined in the context of signs and symptoms of a collection with supporting evidence of urine collection through drainage or aspiration. AM was identified based on postoperative imaging indicative of arteriovenous fistula or pseudoaneurysm and/or requirement for selective embolization. Predictors of AM and UL were assessed by univariate analysis. Results: A total of 395 RPNs were performed by four urologists between January 2014 and October 2018. Tumor complexity, defined by nephrometry score, was significantly greater in the prospective cohort (p = 0.01). Overall incidence of postoperative complications was 5.6% with cohort-specific incidences of 5.3% and 5.8%. The retrospective cohort had a greater percentage of complications classified as ≥IIIa: 8/13 (61.5%) vs 2/8 (25%). Overall incidence of AM was 2.3% with cohort-specific incidence of 3.1% (7/225) vs 1.1% (2/170). Overall incidence of UL was 0.25% with cohort-specific incidence of 0.55% (1/225) and 0.0% (0/170). The difference in incidence of both complications between cohorts was significant (p < 0.05). No significant predictors for AM were identified. Conclusions: The incidence of postoperative complications after RPN remains low (5.3% vs 5.8%, overall: 5.6%). UL and AM are becoming rarer with experience, despite increasing surgical complexity (0.55% vs 0%, 3.1% vs 1.1%).

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