Acute kidney injury: epidemiology and assessment

An evolving understanding of epidemiology and pathophysiology of acute organ dysfunction in the setting of critical illness has given rise to new concepts and terminology for a syndrome once known as either acute tubular necrosis or acute renal failure. Indeed, the clinical syndrome known as acute tubular necrosis does not actually manifest the morphological changes that the name implies. Similarly, a precise biochemical definition of acute renal failure was never proposed, and until recently there has been no consensus on the diagnostic criteria or clinical definition. The RIFLE criteria were developed to achieve diagnostic standardization and the term acute kidney injury (AKI) has been proposed to encompass the entire spectrum of the syndrome from minor changes in renal function to requirement for renal replacement therapy. AKI is not acute tubular necrosis nor is it acute renal failure. Small changes in kidney function in hospitalized patients are important and are associated with significant changes in short and possibly long-term outcomes. The RIFLE criteria provide a uniform definition of AKI and have now been validated in numerous studies. The population incidence of AKI is approximately 2000-3000 patients per million population per year. The incidence of AKI is increasing and ICU 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. Patients with AKI who are treated with RRT, still have a mortality of 50-60 %. Of surviving patients, 5-20 % remain dialysis-dependent at hospital discharge.