Epidemiology of acute kidney injury: How big is the problem?

OBJECTIVE: Acute kidney injury (AKI) is a complication that occurs frequently in hospitalized patients. In this article, we provide an overview of the literature on the epidemiology of AKI in hospitalized patients. PATIENTS AND SETTING: The overview is restricted to hospitalized patients, and most emphasis is put on intensive care unit patients. MEASUREMENTS AND MAIN RESULTS: The population incidence of less severe AKI and AKI treated with renal replacement therapy is approximately 2,000-3,000 and 200-300 per million population per year, respectively. These numbers are comparable with the estimates for severe sepsis and acute lung injury. Approximately 4-5% of general intensive care unit patients will be treated with renal replacement therapy, and up to two thirds of intensive care unit patients will develop AKI defined by the RIFLE classification. The incidence of AKI is increasing. Intensive care unit patients with AKI have a longer length of stay and therefore generate greater costs. In addition, AKI is associated with increased mortality, even after correction for covariates. Increasing RIFLE class is associated with increasing risk of in-hospital death. Patients with AKI who are treated with renal replacement therapy still have a mortality rate of 50-60%. Of surviving patients, 5-20% remain dialysis dependent at hospital discharge. CONCLUSION: AKI has a high incidence, comparable with acute lung injury and severe sepsis, and is associated with higher hospital mortality.