Impact of renal sinus protrusions on achieving trifecta in robot-assisted partial nephrectomy

Objective: The objective of this work is to assess the relationship between the morphological characteristics of a central tumour and the perioperative outcomes of robot-assisted partial nephrectomy (RAPN).Subjects and methods: We retrospectively analysed the data from 186 patients with central tumours involving the renal sinus, who underwent RAPN in a single-centre study between February 2015 and June 2022. All cases were assigned a RENAL nephrometry score based on preoperative images. The shape of the protruding portion of the tumour was classified into four types: 'flat', 'spherical', 'single-hump', and 'complex-hump', and was independently assessed by two readers. The trifecta is defined as the warm ischemia time within 25 min, negative surgical margins, and no major postoperative complications. Univariate and multivariate analyses were performed to identify the factors associated with the failing trifecta.Results: Trifecta was achieved in 113 cases (60.8%), and the achievement rate in flat, spherical, single-hump, and complex-hump types was 83.3%, 74.5%, 64.3%, and 21.3%, respectively. Prolonged warm ischemia time was the primary cause of the failure to achieve the trifecta. The rate of positive surgical margins and upstage to pathological T3a was greater for complex humps while the rate of major complications and postoperative GFR preservation did not differ between shapes. On multivariate analysis for failing trifecta achievement, the complex-hump protrusion was found to be an independent positive predictor (odds ratio: 15.8; p < 0.001), whereas the height and width of protrusion were not significantly related.Conclusions: The degree of difficulty varied among central tumours, and it was not possible to precisely measure it with existing scoring systems. Complex-hump protrusions strongly correlate with failure to achieve the trifecta. Preoperative assessment of the morphology of protrusion is useful for predicting outcomes.