How Does AKI Affect Risk of CKD Progression?

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Once other characteristics are taken into account, patients with chronic kidney disease (CKD) who are hospitalized with mild to moderate acute kidney injury (AKI) have only a small, additional risk of CKD progression, reports a study in the Annals of Internal Medicine.

The analysis included 3150 patients with CKD, drawn from the Chronic Renal Insufficiency Cohort (CRIC) study. The occurrence of “hospitalized AKI” was assessed, defined as at least a 50% increase in inpatient serum creatinine (SCr). The main outcome of interest was kidney function trajectory, with the estimated glomerular filtration rate (eGFR) based on the SCr or cystatin C level.

Over a median of 3.9 years' follow-up, AKI episodes occurred in 433 patients: a rate of 13.7%. Severity was grade 1 or 2 in 92% of cases. Episodes of AKI were associated with reductions in eGFR: −2.30 based on SCr and −3.61 based on cystatin C.

However, after adjustment for other factors, including baseline eGFR and proteinuria, the associated declines in eGFR were much smaller: −0.38 based on SCr and −0.15 based on cystatin C, with overlapping confidence intervals. By both methods, there was a possibility of no effect on changes in the eGFR slope.

Studies have linked AKI to more rapid loss of kidney function, leading to trials of interventions to reduce AKI severity. However, studies of the association between AKI and subsequent changes in eGFR have had important limitations, including inadequate controls for differences between patients with and without AKI.

The new analysis of patients with CKD suggests that mild to moderate episodes of AKI have little or no effect on worsening subsequent kidney function, after adjustment for other variables. “Our results suggest that much of the kidney disease observed after AKI may already be present before AKI,” the researchers write [Muiru AN, et al. Risk for chronic kidney disease progression after acute kidney injury: Findings from the Chronic Renal Insufficiency Cohort study. Ann Intern Med, published online ahead of print July 11, 2023. doi: 10.7326/M22-3617;].