Long-term risk of mortality and other adverse outcomes after acute kidney injury: a systematic review and meta-analysis

Abstract

Background: Acute kidney injury (AKI) is common in hospitalized patients. The impact of AKI on long-term outcomes is controversial.

Study design: Systematic review and meta-analysis.

Setting & participants: Persons with AKI.

Selection criteria for studies: MEDLINE and EMBASE databases were searched from 1985 through October 2007. Original studies describing outcomes of AKI for patients who survived hospital discharge were included. Studies were excluded from review when participants were followed up for less than 6 months.

Predictor: AKI, defined as acute changes in serum creatinine level or acute need for renal replacement therapy.

Outcomes: Chronic kidney disease (CKD), cardiovascular disease, and mortality.

Results: 48 studies that contained a total of 47,017 participants were reviewed; 15 studies reported long-term data for patients without AKI. The incidence rate of mortality was 8.9 deaths/100 person-years in survivors of AKI and 4.3 deaths/100 patient-years in survivors without AKI (rate ratio [RR], 2.59; 95% confidence interval, 1.97 to 3.42). AKI was associated independently with mortality risk in 6 of 6 studies that performed multivariate adjustment (adjusted RR, 1.6 to 3.9) and with myocardial infarction in 2 of 2 studies (RR, 2.05; 95% confidence interval, 1.61 to 2.61). The incidence rate of CKD after an episode of AKI was 7.8 events/100 patient-years, and the rate of end-stage renal disease was 4.9 events/100 patient-years.

Limitations: The relative risk for CKD and end-stage renal disease after AKI was unattainable because of lack of follow-up of appropriate controls without AKI.

Conclusions: The development of AKI, defined as acute changes in serum creatinine level, characterizes hospitalized patients at increased risk of long-term adverse outcomes.

Figure 1. Flow diagram of studies with long term outcomes of AKI that were considered for inclusion

Figure 2. Pooled rate ratio of long-term mortality for survivors of AKI

Overall RR 2.62 (95% CI 1.99-3.45); I² = 86% Abbreviations: Txp, transplantation; RRT, renal replacement therapy; PCI, _{Percutaneous intervention}; LVAD, left ventricular assist device AKI, acute kidney injury.

Figure 3. Pooled rate ratios for long-term death by severity of AKI

A. Mild AKI (Rise in creatinine by 25% or drop in creatinine clearance of > 10%) RR 1.67 (95% CI 1.41-1.98); I² = 0% B. Moderate AKI (Rise in creatinine by > 50%, > 100%, > 1.0 mg/dl, or creatinine concentration of > 1.7 mg/dL) RR 2.70 (95% CI 1.77-4.12), I² = 89% C. Severe AKI (RRT-requiring) RR 3.09 (95% CI 2.20-4.33), I² = 66%