Until 2004, more than 30 different definitions of acute renal failure existed. The RIFLE criteria standardized these and classified them into the stages shown in the table below.
In 2007, the term “Acute Renal Failure” was replaced by the term “Acute Kidney Injury” to more accurately reflect the variation in the disease. In the course of this, the definition as well as the staging was revised again.
Staging of acute renal failure (ANV; acute renal insufficiency).
| RIFLE stage | AKIN stage | Serum creatinine | Urine excretion | Traditional name |
| Risk | 1 | RIFLE/AKIN: 1.5- to 1.9-fold creatinine increase or AKIN: increase of 0.3 mg/dL within 48 h | <0.5 mL/kg bw/h for 6 h | Renal damage |
| Injury | 2 | 2- to 2.9-fold creatinine increase | <0.5 ml/kg bw/h for 12 h | Renal insufficiency |
| Failure | 3 | > 3-fold creatinine increase or increase > 4 mg/dL + acute increase ≥ 0.5 mg/dL | < 0.3 ml/kg bw/h for 24 h or anuria (lack of urine output) for 12 h | Renal failure |
| Loss | – | Renal failure for > 4 weeks | – | |
| ESRD | – | Renal failure for > 3 months | – | Terminal renal failure |
RIFLE stages L and E are late sequelae of acute kidney injury and are no longer included in AKIN stages.
Acute kidney injury (AKI) is present when any of the following criteria are met (AKIN definition):
- Absolute creatinine increase of 0.3 mg/dL or
- Percentage creatinine increase of 1.5 times baseline (AW) within 7 days or
- Decrease in urine excretion < 0.5 ml/kg bw/h for more than 6 hours (within 48 hours)
Different measures are emphasized depending on the stage of acute renal failure:
RIFLE stages R and I/AKIN stages 1 and 2 – early stages of acute renal failure (ANV).
- Stabilization of renal function
- Prevention of progression (progression) of renal failure.
RIFLE stage F/AKIN stage 3
- Consideration of the effects of renal failure on metabolism (metabolism).
- Consideration of the effects of renal replacement therapy
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