Table 1.

Classification systems for acute kidney injury.

I: RIFLE Classification
Stage	GFR criteria	Urine output criteria
Risk	SCr increased 1.5-2 times baseline or GFR decreased >25%	<0.5 mL/kg/hour for <6 hours
Injury	SCr increased 2-3 times baseline or GFR decreased >50%	<0.5 mL/kg/hour for >12 hours
Failure	SCr increased >3 times baseline or GFR decreased 75% or SCr ≥4 mg/dL; acute rise ≥0.5 mg/dL	<0.3 mL/kg/hour for 24 hours (oliguria) or anuria for 12 hours
Loss of function	Persistent acute renal failure: complete loss of kidney function >4 weeks (requiring dialysis)
End-stage renal disease	Complete loss of kidney function >3 months (requiring dialysis)
II. Acute Kidney Injury Network (AKIN)
Abrupt (within 48 hours) reduction in kidney function currently defined as an absolute increase in SCr of 0.3 mg/dL or more (≥26.4 µmol/L) or
A percentage increase in SCr of 50% or more (1.5-fold from baseline) or
A reduction in urine output (documented oliguria of <0.5 mL/kg/hour for >6 hours)
III. Kidney Disease Improving Global Outcomes (KDIGO)
Increase in SCr by 0.3mg/dL or more within 48 hours or
Increase in SCr to 1.5 times baseline or more within the last 7 days or
Urine output <0.5 mL/kg/hour for 6 hours

GFR=glomerular filtration rate;

RIFLE=Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease;

SCr=serum creatinine