Estimated blood loss to urine output ratio during partial nephrectomy as a predictor of postoperative acute kidney injury in a hereditary renal cancer-enriched population.

Introduction: We aimed to assess whether the intraoperative estimated blood loss (EBL) to urine output (UOP) ratio (EBL/UOP) is a predictor of postoperative acute kidney injury (AKI) in a cohort of patients enriched with hereditary renal cancer syndromes undergoing partial nephrectomy (PN).

Methods: We performed a retrospective chart review of patients who underwent PN at our institution from January 2006 to October 2024. We recorded and analyzed the clinical, demographic, and intraoperative characteristics of all patients.

Results: A total of 1166 PNs (761 patients and 5903 renal tumors) were analyzed, of which 484 (41.5%) developed postoperative AKI. The average EBL/UOP was 1.06 (0.46-2.35) for patients without AKI and increased as AKI worsened, with a ratio of 5.00 (2.34-9.43) in patients with KDIGO AKI grade 3 (p<0.001). EBL/UOP was associated with AKI in all patients (odds ratio [OR] 1.079, p=0.002) and those with bilateral native kidneys (OR 1.083, p=0.003). After adjustment in patients with solitary kidney, no AKI association with EBL/UOP (OR 1.039, p=0.447) was found.

Conclusions: EBL/UOP is a novel tool associated with the increased risk of developing post-PN AKI in select patients. In multiplex and repeat PNs, a higher ratio can assist the surgical team in identifying patients at risk of developing AKI. Prospective evaluation involving management strategies based on the EBL/UOP is needed to determine its true utility in clinical practice and generalization in the broader PN population.