Risk, injury, failure, loss of kidney function, and end-stage kidney disease (RIFLE) classification (4).

Class	GFR	Urine Output (UOP)
Risk	↑ SCr × 1.5 or ↓ GFR >25%	<.5 mL/kg/h × 6 hours
Injury	↑ SCr × 2 or ↓ GFR >50%	<.5 mL/kg/h × 12 hours
Failure	↑SCr × 3 or ↓ GFR >75%	<.3 mL/kg/h × 24 hours or anuria × 12 hours
Loss of kidney function	Complete loss of kidney function >4 weeks
End-stage kidney disease	Complete loss of kidney function >3 months

GFR, glomerular filtration rate.