Postoperative Acute Kidney Injury: Focus on Renal Recovery Definitions, Kidney Disease Progression and Survival

The aim of this study was to examine different definitions of renal recovery following postoperative acute kidney injury (AKI) and how these definitions associate with survival and the development and progression of chronic kidney disease (CKD). Methods: This was a retrospective study of all patients who underwent abdominal, cardiothoracic, vascular, or orthopedic surgery at a single university hospital between 1998 and 2015. Recovery of renal function following postoperative AKI was assessed comparing 4 different definitions: serum creatinine (SCr) (i) < 1.1 baseline, (ii) 1.1-1.25 baseline, (iii) 1.25-1.5 baseline, and (iv) > 1.5 baseline. One-year survival and the development or progression of CKD within 5 years was compared with a propensity score-matched control groups. Results: In total, 2,520 AKI patients were evaluated for renal recovery. Risk of incident and progressive CKD within 5 years was significantly increased if patients did not achieve a reduction in SCr to < 1.5 baseline (hazard ratio [HR] 1.50; 95% CI 1.29-1.75) and if renal recovery was limited to a fall in SCr to 1.25-1.5 baseline (HR 1.32; 95% CI 1.12-1.57) within 30 days. The definition of renal recovery that best predicted survival was a reduction in SCr to < 1.5 baseline within 30 days. One-year survival of patients whose SCr decreased to < 1.5 baseline within 30 days was significantly better than that of a propensity scorematched control group that did not achieve renal recovery (85 vs. 71%, p < 0.001). Conclusions: These findings should be considered when a consensus definition of renal recovery after AKI is established.