This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.
What KDIGO staging is
Acute kidney injury (AKI) is a rapid decline in kidney function over hours to days. The 2012 KDIGO (Kidney Disease: Improving Global Outcomes) guideline defines it and grades its severity in three stages, based on the rise in serum creatinine and the fall in urine output. Each stage carries a higher risk of complications, dialysis and death, which is why the stage guides monitoring and care.
The criteria
AKI is present if any of the following applies:
- creatinine rises by ≥ 0.3 mg/dL (26.5 µmol/L) within 48 hours;
- creatinine reaches ≥ 1.5 × baseline within the prior 7 days;
- urine output is < 0.5 mL/kg/h for 6 hours.
| Stage | Creatinine | Urine output |
|---|---|---|
| 1 | 1.5 to 1.9 × baseline, or ≥ 0.3 mg/dL rise | < 0.5 mL/kg/h for 6 to 12 h |
| 2 | 2.0 to 2.9 × baseline | < 0.5 mL/kg/h for ≥ 12 h |
| 3 | ≥ 3.0 × baseline, or ≥ 4.0 mg/dL, or dialysis started | < 0.3 mL/kg/h for ≥ 24 h, or anuria ≥ 12 h |
The final stage is the highest stage reached by either criterion.
Example
Baseline creatinine 1.0 mg/dL, now 2.1 mg/dL, with normal urine output:
- ratio 2.1 × baseline: stage 2 by creatinine;
- absolute rise 1.1 mg/dL;
- final KDIGO stage: 2.
Choosing the baseline
The baseline is the patient’s usual creatinine, ideally a stable value from the previous weeks or months. If none is known, the lowest value during the hospital stay is often used. Some clinicians back-calculate a baseline from an assumed eGFR of 75 mL/min/1.73 m², but that can misclassify patients with chronic kidney disease.
Limits
- Creatinine lags behind the actual injury by 24 to 48 hours, so early AKI can be missed.
- Creatinine depends on muscle mass: low values in frail or amputee patients can hide AKI.
- Urine output criteria need an accurate weight and hourly measurement, usually with a urinary catheter.
- Some drugs, such as trimethoprim or cimetidine, raise creatinine without real kidney injury.
- A diagnosis of AKI should prompt a search for its cause: low blood pressure, dehydration, nephrotoxic drugs, contrast agents, sepsis or urinary obstruction.
For a rough estimate of kidney function once creatinine is stable, see the eGFR calculator; eGFR equations are not valid while creatinine is changing quickly.