The Prognostic Importance of Duration of AKI: a Systematic Review and Meta-analysis

Background: Acute kidney injury (AKI), as defined by peak increase in serum creatinine, is independently associated with increased risk of mortality and length of stay. Studies have suggested that the duration of AKI may be an important additional or independent prognostic marker of increased mortality in patients with AKI across clinical settings. We performed a systematic review and meta-analysis of published studies to assess the impact of duration of AKI on outcomes.

Methods: Various bibliographic databases (MEDLINE, Embase, Cochrane Library, CINAHL and Web of Science) were searched through database inception to December 2015. Human, longitudinal studies with patients aged 18 or above describing outcomes of duration of AKI were included. Duration of AKI categorized as "Short" if AKI duration was ≤2 days or labeled as "transient AKI"; "Medium" for AKI durations 3-6 days and "Long" for AKI duration of ≥7 days or "non-recovered". Various outcomes looked at were Long term mortality, cardiovascular events, chronic kidney disease (CKD).

Results: Eighteen studies were deemed eligible for the systematic review. The outcome of long-term mortality with duration of AKI was reported in 8 studies. The pooled Risk Ratio (RR) for long-term mortality generally was higher for longer duration of AKI: short duration of AKI (n = 8 studies, RR 1.42, 95% CI 1.21-1.66), medium duration (n = 4 studies, RR 1.92, 95% CI 1.34-2.75), and long duration (n = 8 studies, RR 2.28, 95% CI 1.77-2.94) duration of AKI. Further, Duration of AKI was independently associated with higher risk of cardiovascular outcomes and incident CKD Stage 3 when stratified within each stage of AKI.

Conclusion: Duration of AKI was independently associated with long term mortality, cardiovascular(CV) events, and development of incident CKD Stage 3.