Independent association between acute kidney injury and kidney function trajectory

Introduction: It is now universally accepted that acute kidney injury (AKI) is not a limited and entirely reversible condition as many previously thought. However, the independent association between mild to moderate AKI and subsequent kidney function trajectory remains poorly characterized because prior studies have not adequately controlled for pre-existing differences between patients who did or did not develop AKI. Methods: Here, we employed linear mixed-effects regression models to examine the association between an episode of AKI and subsequent trajectory of estimated glomerular filtration rate (eGFR), estimated by serum creatinine (eGFRcr) or cystatin C (eGFRcys), among all 1603 participants in the ASsessment, Serial Evaluation, and Subsequent Sequelae of Acute Kidney Injury (ASSESS-AKI) study. Results: In fully adjusted analysis, mild to moderate AKI (83.1% KDIGO Stage 1, 12.2% KDIGO Stage 2) was independently associated with a small magnitude loss of kidney function, i.e., non-recovery to baseline (-1.32 [95% confidence interval, -2.19 to -0.45] ml/min per 1.73 m² for eGFRcr and -1.59 [-2.44 to -0.74] ml/min per 1.73 m² for eGFRcys). There were no statistically significant changes in eGFR slope after AKI (-0.23 [-0.73 to 0.26] ml/min per 1.73 m² per year for eGFRcr slope and -0.25 [-0.74 to 0.23] ml/min per 1.73 m² per year for eGFRcys slope). Conclusions: After pre-AKI eGFR (slope), pre-AKI proteinuria, and other potential confounders were accounted for, the association between mild to moderate AKI and worsening subsequent kidney function was small. Thus, while mild to moderate AKI can be an initiator or promoter of kidney disease progression, the actual magnitude of its clinical and public health importance is likely limited.