Clinical review: RIFLE and AKIN--time for reappraisal

Abstract

In recent years, the use of the consensus definitions of acute kidney injury (RIFLE and AKIN) in the literature has increased substantially. This indicates a highly encouraging acceptance by the medical community of a unifying definition for acute kidney injury. This is a very important and positive step in the right direction. There remains some variation in how the criteria are interpreted and used in the literature, including use/nonuse of urine output criteria, use of change in estimated glomerular filtration rate rather than change in creatinine, and choice of baseline creatinine. The present review is intended to aid the reader in critically appraising studies using these consensus definitions. Since no single definition will be perfect, a logical next step would be to reconcile existing definitions, moving the medical community towards using a single consensus definition as has been done with sepsis and acute lung injury/acute respiratory distress syndrome. As new data emerge, integration of novel biomarkers into the consensus definition will be a welcome refinement.

Figure 1

RIFLE and AKIN classifications for acute kidney injury. Risk–Injury–Failure–Loss–Endstage renal disease (RIFLE) and Acute Kidney Injury Network (AKIN) classifications for acute kidney injury (adapted from [6,7]). ARF, acute renal failure; Cr, creatinine; GFR, glomerular filtration rate.

Figure 2

Mortality by RIFLE class. Mortality (relative risk (RR) and 95% confidence interval) by Risk–Injury–Failure–Loss–Endstage renal disease class (data from [8]). AKI, acute kidney injury.

Figure 3

RIFLE class and mortality in different patient populations. Risk–Injury–Failure–Loss–Endstage renal disease class and mortality in different patient populations (data from [8]). NonAKI, no acute kidney injury; Cr, creatinine; ICU, intensive care unit; RR, relative risk.