Table 1. RIFLE and AKIN classification schemes for AKI .

	GFR criteria	Urine output criteria
RIFLE: an acute rise of SCr over 7 days
Risk	Increase in SCr ≥ 1.5 × baseline or decrease in GFR ≥ 25%	UO < 0.5 ml/kg/h × 6 h
Injury	Increase in SCr ≥ 2.0 × baseline or decrease in GFR ≥ 50%	UO < 0.5 ml/kg/h × 12 h
Failure	Increase in SCr ≥ 3.0 × baseline or SCr ≥ 4.0 mg/dl (354 μmol/l) or decrease in GFR ≥ 75%	UO < 0.3 ml/kg/h × 24 h or anuria × 12 h
Loss	Complete loss of kidney function > 4 weeks
ESKD	End stage renal disease (> 3 months)
AKIN: an acute rise of SCr within 48 h
Stage 1	Same as RIFLE-Risk plus increase in SCr ≥ 0.3 mg/dl (≥ 26.4 μmol/l)	Same as RIFLE
Stage 2	Same as RIFLE-Injury
Stage 3	Same as RIFLE-Failure plus initiation of RRT

AKIN, acute kidney injury network; ESKD, end-stage kidney disease; GFR, glomerular filtration rate; RIFLE, risk of renal failure, injury to the kidney, failure of kidney function, loss of kidney function, and end-stage renal failure; RRT, renal replacement therapy; SCr, serum creatinine; UO, urine output.