Impact of Prolonged Warm Ischemia During Clamped Partial Nephrectomy: Comparison Between Japanese and American Cohorts

Introduction Recent research suggests that functional recovery begins to decline after ≈30 min of warm‐ischemia time (WIT) following clamped partial nephrectomy (PN). However, the extent of this decline and populations at risk remain unclear. Our objective was to identify factors associated with functional decline following prolonged WIT in Japanese and American patients. Methods A multi‐institutional retrospective review of PN patients managed with prolonged WIT (> 30 min) at Tokyo Women's and Cleveland Clinic (2010–2024). Inclusion required pre‐and post‐operative serum creatinine and cross‐sectional imaging. Ipsilateral split renal function (SRF) was assessed using parenchymal volume analysis (PVA). Recovery from ischemia (Rec Ischemia ) was defined as ipsilateral GFR preserved normalized by percent parenchymal volume preserved (PPVP). Multivariable analysis identified factors associated with Rec Ischemia , PPVP, and % global GFR preservation. Results 300 U.S./171 Japanese patients met inclusion criteria. U.S. patients had increased comorbidities, including obesity, hypertension, and cardiovascular disease. A significant and similar decline in global GFR for every additional 10 min of WIT was seen in both the Japanese and U.S. patients (3.1% vs. 4.0%, respectively, p = 0.41). Independent predictors of decline in global GFR were PPVP in both cohorts and longer WIT only for U.S. patients. R.E.N.A.L. and tumor size were primary drivers of decline in PPVP, and WIT and HTN were drivers of decline in Rec Ischemia , but only in U.S. patients. Conclusion Japanese and U.S. patients undergoing PN with prolonged WIT experienced a similar decline in global GFR, albeit driven by different factors potentially reflecting differences in patient populations and/or surgical technique. Our data suggest that avoiding prolonged WIT may be important in patients with solitary kidneys and/or severe CKD, although further studies will be needed.