What is the RIFLE (Risk of renal dysfunction, Injury to the kidney, Failure or Loss of kidney function, and End-stage kidney disease) classification system for acute kidney injury (AKI)?

Updated: Dec 24, 2020
  • Author: Biruh T Workeneh, MD, PhD, FASN; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

In 2004, the Acute Dialysis Quality Initiative work group set forth a definition and classification system for acute renal failure, described by the acronym RIFLE (Risk of renal dysfunction, Injury to the kidney, Failure or Loss of kidney function, and End-stage kidney disease). [2] Investigators have since applied the RIFLE system to the clinical evaluation of AKI, although it was not originally intended for that purpose. AKI research increasingly uses RIFLE. See Table 1, below.

Table 1. RIFLE Classification System for Acute Kidney Injury (Open Table in a new window)

Stage

GFR** Criteria

Urine Output Criteria

Probability

Risk

SCreat increased × 1.5

or

GFR decreased >25%

UO< 0.5 mL/kg/h × 6 h

High sensitivity (Risk >Injury >Failure)

Injury

SCreat increased × 2

or

GFR decreased >50%

UO < 0.5 mL/kg/h × 12 h

Failure

SCreat increased × 3

or

GFR decreased 75%

or

SCreat ≥4 mg/dL; acute rise ≥0.5 mg/dL

UO < 0.3 mL/kg/h × 24 h

(oliguria)

or

anuria × 12 h

Loss

Persistent acute renal failure: complete loss of kidney function >4 wk

High specificity

ESKD*

Complete loss of kidney function >3 mo

*ESKD—end-stage kidney disease; **GFR—glomerular filtration rate; †SCreat—serum creatinine; ‡UO—urine output

Note: Patients can be classified by GFR criteria and/or UO criteria. The criteria that support the most severe classification should be used. The superimposition of acute on chronic failure is indicated with the designation RIFLE-FC; failure is present in such cases even if the increase in SCreat is less than 3-fold, provided that the new SCreat is greater than 4.0 mg/dL (350 µmol/L) and results from an acute increase of at least 0.5 mg/dL (44 µmol/L).

When the failure classification is achieved by UO criteria, the designation of RIFLE-FO is used to denote oliguria.

The initial stage, risk, has high sensitivity; more patients will be classified in this mild category, including some who do not actually have renal failure. Progression through the increasingly severe stages of RIFLE is marked by decreasing sensitivity and increasing specificity.


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