Risk factors for major adverse kidney events in the first year after acute kidney injury

Background: Acute kidney injury (AKI) survivors are at increased risk of major adverse kidney events (MAKEs), including chronic kidney disease (CKD), end-stage kidney disease (ESKD) and death. High-risk AKI patients may benefit from specialist follow-up, but factors associated with increased risk have not been reported. Methods: We conducted a retrospective study of AKI patients admitted to a single centre between 2012 and 2016 who had a baseline estimated glomerular filtration rate (eGFR) >30 mL/min/1.73 m2 and were alive and independent of renal replacement therapy (RRT) at 30 days following discharge. AKI was identified using International Classification of Diseases, Tenth Revision codes and staged according to the Kidney Disease: Improving Global Outcomes criteria. Patients were excluded if they were kidney transplant recipients or if AKI was attributed to intrinsic kidney disease. We performed Cox regression models to examine MAKEs in the first year, defined as the composite of CKD (sustained 25% drop in eGFR), ESKD (requirement for chronic RRT or sustained eGFR <15 mL/min/1.73 m2) or death. We examined secondary outcomes (CKD, ESKD and death) using Cox and competing risk regression analyses. Results: We studied 2101 patients (mean ± SD age 69 ± 15 years, baseline eGFR 72 ± 23 mL/min/1.73 m2). Of these, 767 patients (37%) developed at least one MAKE (429 patients developed CKD, 21 patients developed ESKD, 375 patients died). MAKEs occurred more frequently with older age [hazard ratio (HR) 1.16 per decade, 95% confidence interval (CI) 1.10-1.24], greater severity of AKI (Stage 2 HR 1.38, 95% CI 1.16-1.64; Stage 3 HR 1.62, 95% CI 1.31-2.01), higher serum creatinine at discharge (HR 1.04 per 10 µmol/L, 95% CI 1.03-1.06), chronic heart failure (HR 1.41, 95% CI 1.19-1.67), liver disease (HR 1.68, 95% CI 1.39-2.03) and malignancy (non-metastatic HR 1.44, 95% CI 1.14-1.82; metastatic HR 2.26, 95% CI 1.80-2.83). Traditional risk factors (e.g. diabetes and cardiovascular disease) had limited predictive value. Conclusions: More than a third of AKI patients develop MAKEs within the first year. Clinical variables available at the time of discharge can help identify patients at increased risk of such events.