Determinants of early acute kidney injury after robot-assisted partial nephrectomy: a single-institution analysis of a prospectively maintained cohort

PURPOSE: To adjudicate in a homogeneous cohort of robot-assisted partial nephrectomy (RAPN) the competing determinants of early acute kidney injury (AKI) within a single framework and compare the discriminative value of the RENAL, PADUA, and contact surface area (CSA) nephrometry scores. METHODS: Consecutive patients undergoing RAPN were included from the prospectively maintained institutional database. Early AKI was defined by the AKIN criteria as a rise in serum creatinine on the first postoperative day (POD1). Score discrimination was quantified using the area under the ROC curve (AUC) with DeLong's test; independent determinants were identified with a parsimonious multivariable logistic model; and the perioperative biochemical response was described. Continuous variables were compared with Mann-Whitney U; categorical with Fisher tests. RESULTS: Among 297 RAPN, early AKI occurred in 38 (12.8%). PADUA discriminated AKI best (AUC 0.73), followed by RENAL (0.69) and CSA (0.62); pairwise differences were not significant (PADUA vs RENAL P=0.06). On multivariable analysis, a higher PADUA score (adjusted OR [aOR] 1.61 per point, 95% CI 1.29-2.00) and male sex (aOR 2.91, 1.05-8.09) were independently associated with AKI (AUC 0.76); results were consistent using RENAL. Warm ischemia time was associated with AKI on univariable analysis but was strongly correlated with complexity (r=0.54) and lost significance after adjustment for PADUA (aOR 1.01, P=0.70). Early AKI was accompanied by a greater hemoglobin drop (2.2 vs 1.8 g/dL; P=0.006) and more transfusions (16% vs 1%), and by an eGFR nadir on POD1 (49 vs 80 mL/min) that partly recovered by discharge. A pre-specified POD1-POD3 sensitivity analysis increased incidence to 19.8% but attenuated score discrimination, without changing association direction. CONCLUSIONS: In a homogeneous RAPN cohort, early AKI affects roughly one in eight patients and was associated with anatomical tumor complexity rather than with ischemia time, whose association appeared to reflect tumor complexity rather than a true ischemic effect. PADUA showed the highest discrimination, not significantly different from RENAL, while CSA added least.