The association between elevated preoperative red cell distribution width and worsening kidney function after noncardiac operation. A propensity score and competing risk weighted retrospective cohort study.

Background: Elevated red cell distribution width (RDW) is associated with increased postoperative mortality, but less is known about kidney outcomes. This study investigated the association between elevated preoperative RDW and postoperative worsening of long-term kidney function and incidence of acute kidney injury. Methods: This retrospective cohort study included patients ≥18 yr undergoing noncardiac operation at Landspitali-The National University Hospital of Iceland between 2005 and 2018. Outcomes were compared between groups with elevated preoperative RDW (13.3-14.0%, 14.0-14.7%, 14.7-15.8%) and a propensity score-matched cohort (RDW ≤13.3%) using Fine-Gray competing risk regression analysis, with death as a competing event. The primary outcome was time to worsening of at least one estimated glomerular filtration rate (eGFR) category sustained for 3 months. Secondary outcomes were acute kidney injury, length of hospital stay, and 30-day readmission rate. Results: Out of 63 056 operations included in this study, 55 724 were available for propensity score-matched analysis. The hazard of long-term eGFR worsening was higher for patients with RDW between 14.0% and 14.7%: hazard ratio (HR) 1.23 (95% confidence interval [CI] 1.13-1.35), 14.7% and 15.8%: HR 1.20 (95% CI 1.07-1.34), and >15.8%: HR 1.16 (95% CI 1.00-1.34) compared with matched controls (RDW <13.3%), adjusted for death as a competing event. For secondary outcomes there was no difference in acute kidney injury, but increased risk of readmission for patients with RDW of 14.0-14.7% (9.8% Conclusions: Elevated preoperative RDW was associated with long-term worsening of eGFR category after operation.