AKI is staged according to the serum creatinine changes, and/or the production of urine.

Stage Creatinine Urine production
1 Increase 1.5-1.9x baseline < 0.5ml/kg/h for >6 consecutive hours
2 Increase 2.0-2.9x baseline < 0.5ml/kg/h for >12 consecutive hours
3 Increase > 3x baseline or >354 µmol/L < 0.3ml/kg/h for > 24h or anuric for 12h

Additionally, a patient is deemed in stage 3 AKI if they are commenced on renal replacement therapy irrespective of creatinine or urine production.

References.

  1. MD, P. R. B., MD, J. A. K., & MD, C. R. (2012). Acute kidney injury. The Lancet, 380(9843), 756–766.
  2. Bellomo R, Ronco C, Kellum JA, Mehta RL, Palevsky P, and the Acute Dialysis Quality Initiative workgroup. Acute renal failure— definition, outcome measures, animal models, fluid therapy and information technology needs: the second international consensus conference of the Acute Dialysis Quality Initiative Group. Crit Care 2004; 8: R204–R12.