Determinants of access route in single-port off-clamp robotic partial nephrectomy: A contemporary cohort study

In off-clamp single-port robot-assisted partial nephrectomy (ocSP-RAPN), the factors guiding retroperitoneal versus transperitoneal access remain undefined. We sought to identify the preoperative and anatomical determinants influencing route selection during early ocSP-RAPN integration at a high-volume centre.

All patients undergoing ocSP-RAPN between May 2024 and October 2025 (n = 78) were retrospectively reviewed. Clinical, anatomical and perioperative variables were compared by access route (retroperitoneal n = 42; transperitoneal n = 36). Tumour complexity was graded using the RENAL score; renal function was evaluated through serial CKD-EPI eGFR measurements. Predictors of retroperitoneal access were analysed using Firth-corrected logistic regression, with covariate entry based on univariable p < 0.20 or biological plausibility. Model calibration, discrimination and collinearity were assessed. Complete-case analysis yielded a final multivariable cohort of 71 patients.

Baseline characteristics were comparable (each each p ≥ 0.23). Tumour size (median 2.5 cm; p = 0.57), preoperative eGFR (p = 0.39) and RENAL complexity (21.6% vs 11.8% high-complexity; p = 0.43) showed no significant differences. Perioperative outcomes were favourable: hospital stay remained 2 days (p = 0.67), complications were uncommon in both groups (≤ 10%; p = 0.82) and all margins were negative. Early renal function was preserved in both cohorts (median ΔeGFR 98.4%; p = 0.61). At multivariable analysis, the RENAL score was the only independent determinant of retroperitoneal access (OR 0.58; 95% CI 0.33-0.97; p = 0.039). The predicted probability of retroperitoneal use decreased from approximately 65% (RENAL ≤ 5) to ~ 20% (RENAL ≥ 9).

In ocSP-RAPN, access selection is shaped predominantly by anatomical complexity, with patient-level variables exerting no measurable influence. When tailored to tumour anatomy, both retroperitoneal and transperitoneal routes ensured safe resection and preserved early renal function. Larger, standardised multicentre cohorts will be required to verify whether these patterns persist beyond specialised environments.