RIFLE/AKIN - Acute Kidney Injury Classification
Classify acute kidney injury (AKI) severity using RIFLE and AKIN criteria based on creatinine changes and urine output.
Important Medical Disclaimer
This calculator is an educational and clinical decision support tool. Results DO NOT replace professional medical evaluation, laboratory tests, or clinical judgment. Always consult a qualified healthcare professional for diagnosis, treatment, and clinical decisions. Calculations are based on scientifically validated formulas but may not be applicable to all patients.
About RIFLE/AKIN
RIFLE Criteria
- Risk: SCr increase 1.5x OR UO <0.5 mL/kg/h for 6h
- Injury: SCr increase 2x OR UO <0.5 mL/kg/h for 12h
- Failure: SCr increase 3x OR SCr ≥4 mg/dL with acute rise ≥0.5 OR UO <0.3 mL/kg/h for 24h
- Loss: Persistent acute renal failure >4 weeks
- ESKD: End Stage Kidney Disease >3 months
AKIN Criteria
- Stage 1: SCr increase ≥0.3 mg/dL OR 1.5-2x baseline OR UO <0.5 mL/kg/h for 6h
- Stage 2: SCr increase 2-3x baseline OR UO <0.5 mL/kg/h for 12h
- Stage 3: SCr increase 3x baseline OR SCr ≥4 mg/dL with acute rise ≥0.5 OR UO <0.3 mL/kg/h for 24h OR anuria for 12h
Clinical Use
Both RIFLE and AKIN are internationally recognized criteria for defining and stratifying acute kidney injury. They help clinicians identify AKI early, assess severity, and guide treatment decisions including need for renal replacement therapy.
Note: AKIN Stage 3 includes need for renal replacement therapy regardless of other criteria. Both systems use the worst criterion (creatinine or urine output) to determine stage.
Frequently Asked Questions
What is the difference between RIFLE and AKIN?
RIFLE was developed in 2004 with 5 stages (Risk, Injury, Failure, Loss, ESKD) using relative creatinine increases. AKIN (2007) simplified to 3 stages and added the criterion of absolute creatinine increase ≥0.3 mg/dL within 48h, making it more sensitive for detecting early AKI. In practice, both are complementary and often used together.
Why is urine output important in AKI assessment?
Oliguria (reduced urine output) is often the first sign of acute kidney injury, preceding serum creatinine elevation by 24-48h. Monitoring urine output enables early detection and faster intervention. Additionally, the severity and duration of oliguria correlate with worse clinical outcomes and higher need for dialysis.
Which criterion to use: creatinine or urine output?
Always use the worst criterion between creatinine and urine output to classify AKI stage. For example, if creatinine indicates Stage 1 but urine output indicates Stage 2, the patient is classified as Stage 2. This ensures the true severity of kidney injury is not underestimated.
How to obtain baseline creatinine if the patient has no prior labs?
When no prior creatinine is available, baseline creatinine can be estimated using the reverse MDRD equation, assuming a GFR of 75 mL/min/1.73m² (per KDIGO recommendations). Alternatively, use the lowest creatinine value in the first 48h of admission. In some cases, admission creatinine is considered baseline, though this may underestimate AKI severity.