Exploring the effect of patient characteristics on the association between warm ischemia time and the risk of postoperative acute kidney injury after partial nephrectomy.

Background: The impact of warm ischemia time (WIT) on renal function after partial nephrectomy (PN) remains debated. This study investigates the effect of WIT on the relationship between preoperative comorbidities and postoperative renal function impairment in renal cell carcinoma (RCC) patients.

Methods: Patients undergoing PN for T1 RCC at a European high-volume center (2000-2023) were analyzed. Logistic regressions assessed the association between patient comorbidities and acute kidney injury (AKI). Patients were stratified into low (LR), intermediate (IR), and high-risk (HR) groups based on a weighted comorbidity score derived from odds-ratio obtained from the logistic regression analysis. Interaction terms and a weighted local polynomial smoother function assessed the impact of WIT on AKI. Cox regressions and cumulative incidence were used to assess the chronic kidney disease (CKD) upstage ≥IIIB risk according to AKI and risk groups.

Results: Of 1,048 patients, 802 underwent PN with warm ischemia. Among these, 339(42%), 208(26%), 255(32%) were classified as LR, IR and HR. IR (OR:1.82, P = 0.018) and HR (OR:3.01, P < 0.001) patients had a higher AKI risk compared to LR. The increase in WIT had little impact on the LR AKI probability compared to IR (OR:1.06, P = 0.001) and HR (OR:1.08, P < 0.001). The 10-year risk of CKD-upstage ≥IIIB was higher (36% vs. 12%, HR:2.40, P = 0.004) after AKI, and in the HR group (HR:2.42, P = 0.008) CONCLUSIONS: WIT predominantly affected the risk of AKI in HR patients for renal function impairment after surgery. Preoperative counseling is essential for comorbid patients, especially when planning complex surgeries with prolonged ischemia, to mitigate AKI and long-term renal impairment.