Nephrometry scores differ in their association with warm ischemia time during robot-assisted partial nephrectomy: comparison of RENAL, RPN, PADUA, and SPARE.

Nephrometry systems are widely used before robot-assisted partial nephrectomy (RAPN), but their relation to intraoperative complexity may differ. We compared RENAL, RPN, PADUA, and SPARE using continuous warm ischemia time (WIT) and assessed whether the scores added information beyond tumor diameter and routine clinical variables. We retrospectively analyzed 579 single-tumor RAPN cases with complete data for all four scores (2016-2023). Associations with WIT were assessed using Spearman correlations and patient-level paired bootstrap comparisons. Tumor diameter was evaluated as an additional comparator. Incremental value was assessed by adding each nephrometry score to a baseline model containing tumor diameter, age, sex, body mass index, laterality, surgeon experience, surgical approach, and fiscal year. Model performance was evaluated using adjusted R² and 10-fold cross-validation. RPN showed the strongest correlation with WIT (ρ = 0.553), followed by tumor diameter (ρ = 0.519). The difference between them was small (Δρ = 0.034, 95% CI - 0.020 to 0.089). RPN had the highest adjusted R² (0.341) among single-predictor models. All four scores improved the baseline model; the numerically largest improvement was observed with PADUA (Δ adjusted R²=0.096; Δ cross-validated RMSE = - 0.397 min). RPN had the strongest stand-alone association with WIT, but its correlation was not clearly stronger than that of tumor diameter. Each nephrometry score added information beyond tumor diameter and routine clinical variables, with the magnitude of incremental improvement differing among systems.