Renal Functional Outcomes in Robot-Assisted Partial Nephrectomy with Minimum Layer Resection Using Virtual Three-Dimensional Image Assistance

Abstract

Background: Robot-assisted partial nephrectomy (RAPN) is a standard approach for localized renal cell carcinoma (RCC), emphasizing renal functional preservation. The Minimum Layer Resection (MLR) method, guided by 3D virtual partial nephrectomy (3DvPN) planning, was developed to balance oncological safety with parenchymal preservation. This study evaluated functional and oncological outcomes of RAPN with MLR and identified predictors of renal functional decline. Methods: We retrospectively analyzed 237 patients (after screening 312 cases) who underwent RAPN between 2012 and 2022 with ≥36-month follow-up. 3DvPN planning was used to guide MLR when feasible; both MLR and non-MLR were available and applied throughout the study period according to predefined indications. The primary endpoint was the percentage of estimated glomerular filtration rate (eGFR) preservation at 36 months; a ≥10% decline was clinically significant. Secondary endpoints included perioperative outcomes, acute kidney injury (AKI), and oncological outcomes such as margin involvement and recurrence. Results: The median age was 60 years, tumor size 29 mm, and warm ischemia time 21 min, with selective or superselective clamping achieved in 62.8% of cases. Postoperative AKI occurred in 25.0% (no patient required dialysis). At 3 years, the median eGFR preservation rate was 84.4%, and 28.5% of patients experienced a ≥10% decline. Independent predictors of short-term decline (14 days) were BMI > 25 kg/m2, AKI, and WIT > 25 min, whereas long-term decline (36 months) was associated with tumor size > 30 mm and WIT > 25 min. Margin involvement was 1.7%, recurrence 3.8%, and major complications (Clavien–Dindo ≥IV) occurred in 1.7%. Conclusions: In conclusion, RAPN with the MLR technique under 3DvPN guidance demonstrated favorable perioperative outcomes, acceptable oncologic safety, and good mid-term renal functional preservation (up to 36 months). The approach provides a reproducible surgical strategy that maximizes parenchymal preservation while maintaining negative surgical margins. Prospective multicenter studies with longer follow-up are warranted to confirm long-term durability and to define the role of MLR in routine practice.