Staging of severity of acute kidney injury
In addition to standardizing the definitions of acute kidney injury, the RIFLE, AKIN, and KDIGO criteria stage the severity of acute kidney injury by the magnitude of change in creatinine or the duration of oliguria.
The RIFLE criteria stratified acute kidney injury into three strata of severity (Risk, Injury, and Failure) on the basis of either change in serum creatinine (≥50%, ≥100%, or ≥200% increase) or the duration of oliguria (≥6 hours, ≥12 hours, or ≥24 hours) and two outcome stages based on the duration of kidney failure.
The subsequent AKIN and KDIGO criteria kept the initial three strata of severity (now called Stage 1, Stage 2, and Stage 3) but dropped the two outcome stages. In all three classification systems, the increasing severity of acute kidney injury is associated with the increasing risk of death and intensive care unit and hospital length of stay.
The duration of acute kidney injury, which is not included in these staging criteria, is also associated with mortality risk.
While these classification systems are important for epidemiologic studies and clinical trials, there remains uncertainty regarding the utility of acute kidney injury staging when applied prospectively in clinical practice.
