AKI and renal drug dosing

KDIGO definition and staging

Reviewed Nov 2026·1 references
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Define and stage AKI with creatinine and urine output, and recognise who needs urgent nephrology/ICU input.

Definition
AKI (KDIGO 2012) = creatinine rise ≥ 0.3 mg/dL within 48 h, OR rise to ≥ 1.5x baseline within the prior 7 days, OR urine output < 0.5 mL/kg/h for 6 h.

At the bedside

  1. 1

    Find a baseline creatinine

    Lowest value in the last 3 months (or up to 1 year). If unknown, use the lowest value during admission; avoid back-calculating from eGFR in Indian patients with low muscle mass.

  2. 2

    Stage by the worse of creatinine or urine output

    Stage 1: 1.5-1.9x baseline or ≥ 0.3 mg/dL rise; UO < 0.5 mL/kg/h for 6-12 h. Stage 2: 2.0-2.9x; UO < 0.5 mL/kg/h ≥ 12 h. Stage 3: ≥ 3x or creatinine ≥ 4.0 mg/dL or RRT started; UO < 0.3 mL/kg/h ≥ 24 h or anuria ≥ 12 h.

  3. 3

    Measure urine output hourly

    Urinary catheter in critically ill/oliguric patients; use actual body weight (consider ideal weight in obesity).

  4. 4

    Apply the KDIGO bundle at any stage

    Stop nephrotoxins (NSAIDs, aminoglycosides, contrast if avoidable), review drug doses, ensure volume status and perfusion pressure (MAP ≥ 65), monitor creatinine and UO, avoid hyperglycaemia, consider alternatives to radiocontrast.

  5. 5

    Escalate stage 2-3

    Nephrology/ICU review, search for cause (see AKI work-up), assess RRT needs (hyperkalaemia, acidosis, overload, uraemic complications).

KDIGO AKI staging

StageSerum creatinineUrine output
11.5-1.9x baseline OR ≥ 0.3 mg/dL rise in 48 h< 0.5 mL/kg/h for 6-12 h
22.0-2.9x baseline< 0.5 mL/kg/h for ≥ 12 h
3≥ 3x baseline OR ≥ 4.0 mg/dL OR RRT initiated< 0.3 mL/kg/h for ≥ 24 h OR anuria ≥ 12 h
Red flag · call your senior now
AKI with K ≥ 6.5 mmol/L, pH < 7.15, pulmonary oedema not responding to diuretics, or uraemic encephalopathy/pericarditis: emergency RRT assessment.
Pitfall
Creatinine lags 24-48 h behind injury, and fluid overload dilutes it; urine output falls earlier.
Pitfall
Using eGFR equations in unstable AKI: they assume steady state.
Pearl
A small creatinine rise (0.3 mg/dL) independently predicts mortality; treat it seriously.

Calculators for this topic

Creatinine clearance (Cockcroft-Gault)

(140 − age) × weight ÷ (72 × creatinine), × 0.85 if female. Not valid in unstable AKI.

References

  1. 1

    Kidney Disease: Improving Global Outcomes (KDIGO) AKI Work Group. KDIGO Clinical Practice Guideline for Acute Kidney Injury. Kidney Int Suppl 2012;2:1-138 (summary: Nephron Clin Pract 2012;120:c179-84).

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AKI work-up

Educational reference for trained clinicians. Check doses against your hospital protocol and the patient in front of you.