Acute Kidney Injury Recovery Pattern and Subsequent Risk of CKD: An Analysis of Veterans Health Administration Data

Background Studies suggest an association between acute kidney injury (AKI) and long-term risk for chronic kidney disease (CKD), even following apparent renal recovery. Whether the pattern of renal recovery predicts kidney risk following AKI is unknown. Study Design Retrospective cohort. Setting & Participants Patients in the Veterans Health Administration in 2011 hospitalized (>24 hours) with at least 2 inpatient serum creatinine measurements, baseline estimated glomerular filtration rate > 60 mL/min/1.73 m2 , and no diagnosis of end-stage renal disease or non−dialysis-dependent CKD: 17,049 (16.3%) with and 87,715 without AKI. Predictor Pattern of recovery to creatinine level within 0.3 mg/dL of baseline after AKI: within 2 days (fast), in 3 to 10 days (intermediate), and no recovery by 10 days (slow or unknown). Outcome CKD stage 3 or higher, defined as 2 outpatient estimated glomerular filtration rates < 60 mL/min/1.73 m2 at least 90 days apart or CKD diagnosis, dialysis therapy, or transplantation. Measurements Risk for CKD was modeled using modified Poisson regression and time to death-censored CKD was modeled using Cox proportional hazards regression, both stratified by AKI stage. Results Most patients’ AKI episodes were stage 1 (91%) and 71% recovered within 2 days. At 1 year, 18.2% had developed CKD (AKI, 31.8%; non-AKI, 15.5%; P < 0.001). In stage 1, the adjusted relative risk ratios for CKD stage 3 or higher were 1.43 (95% CI, 1.39-1.48), 2.00 (95% CI, 1.88-2.12), and 2.65 (95% CI, 2.51-2.80) for fast, intermediate, and slow/unknown recovery. A similar pattern was observed in subgroup analyses incorporating albuminuria and sensitivity analysis of death-censored time to CKD. Limitations Variable timing of follow-up and mostly male veteran cohort may limit generalizability. Conclusions Patients who develop AKI during a hospitalization are at substantial risk for the development of CKD by 1 year following hospitalization and timing of AKI recovery is a strong predictor, even for the mildest forms of AKI.