Acute kidney injury: A definition with a rich past and an evolution

The term acute kidney injury (AKI) appeared in the society of nephrology in 2004 mirroring a key station of the constant development of the whole entity of acute renal failure. The long route from “acute Bright's disease” in the 19th century to modern “acute kidney stress” reflects the continuous effort of the society of nephrology to set the appropriate criteria and finally to formulate a precise and consensus definition in nomenclature of kidney injury. The most important definitions were the Risk, Injury, Failure, Loss of Kidney Function, and End-Stage Kidney Disease in 2004, Acute Kidney Injury Network (AKIN) in 2007, and Kidney Disease Improving Global Outcomes (KDIGO) in 2012 which had been proposed by the committees of Acute Dialysis Quality Initiative, AKIN, and KDIGO, respectively. Common basis of the above definitions was the clinical-laboratory criteria of urine output and serum creatinine while the target of every newer attempt was to increase the sensitivity of AKI and to offer a globally unified perception in terms of diagnosis and prevention. Since the emersion of KDIGO definition, the interest in defining AKI has been focused on the stage that precedes renal damage by the detection of clinically reliable biomarkers. Subsequently, the concept of acute injury is being lately realized as an attack in correspondence with heart attack or even more as an acute stress which can only be witnessed by the appropriate biomarkers. Recent research is focusing on the discovery of the ideal biomarker which must meet the requirements of high specificity, low cost, and ease of application.