Acute kidney injury (AKI) is known to increase in-hospital mortality, but new findings suggest that it also increases long-term mortality risk independent of residual kidney function.

Jean-Philippe Lafrance, MD, and Donald R. Miller, ScD, of Boston University, identified veterans with a first hospitalization between 2000 and 2005 and followed subjects from 90 days after discharge (the index date) until death or the end of the study.

The researchers excluded from analysis patients who underwent dialysis or died before the index date, were hospitalized in the 30 days after discharge, or had an estimated glomerular filtration rate below 30 mL/min/1.73 m2 before AKI.

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AKI cases were identified from laboratory data using an adaptation of the Acute Kidney Initiative Network definition. AKI events were classified by stage (I, II, or III).

Of 864,933 hospitalizations, 82,711 involved AKI (stage I: 52,338; stage II: 19,771; stage III: 10,602). A total of 17.4% of patients died (29.8% with AKI and 16.1% without), the investigators reported at the Canadian Society of Nephrology Annual Meeting in Edmonton, Alberta. AKI was associated with a 41% increased risk of death after adjusting for confounders.

Mortality risk rose with increasing AKI stage: 36%, 46%, and 59% greater risk with stage I, II, and III AKI, respectively.

Given that patients survived 90 days after discharge, the researchers concluded that AKI is associated with an increased mortality risk independent of residual kidney function.