Table 1. Evolution of consensus definitions for AKI.

Criteria	RIFLE25	AKIN26	KDIGO27,92
Date of release	2004	2007	2012
Baseline	Not specifically defined. If not available, back-calculate a serum creatinine using an eGFR of 75 ml/min/1.73 m2 using the MDRD equation	48-h window	Not specifically defined. If not available, use lowest serum creatinine during hospitalization, or calculate SCr using MDRD assuming baseline eGFR 75 ml/min/1.73 m2 when there is no evidence of CKD
Time interval	Diagnosis and staging: within 1–7 days and sustained more than 24 h	Diagnosis: within 48 h Staging: 1 week	Diagnosis: 50% increase in SCr within 7 days or 0.3 mg/dl (26.5 μmol/l) within 48 h

Criteria		Creatinine	Urine output		Creatinine (urine output criteria same)		Creatinine (urine output criteria same)
Stage	Risk	Increased SCr 1.5–1.9 times baseline or GFR decrease >25%	<0.5 ml/kg/h for 6–12 h	1	Increased SCr 1.5–1.9 times baseline OR ⩾0.3 mg/dl (⩾26.5 μmol/l) increase	1	Increased SCr 1.5–1.9 times baseline (7 days) OR ⩾0.3 mg/dl (⩾26.5 μmol/l) increase (48 h)
	Injury	2.0–2.9 times baseline or GFR decrease >50%	<0.5 ml/kg/h for ⩾12 h	2	Same as RIFLE minus eGFR criteria	2	same as AKIN
	Failure	3.0 times baseline, GFR decrease >75%, or SCr ⩾4.0 mg/dl (354 μmol/l) with an acute rise of ⩾0.5 mg/dl (44 μmol/l)	<0.3 ml/kg/h for ⩾24 h OR Anuria for ⩾12 h	3	Same as RIFLE or on RRT. eGFR criteria removed	3	3.0 times baseline, OR Increase in SCr ⩾4.0 mg/dl (354 μmol/l) OR Initiation of renal replacement therapy OR For <18 years, decrease in eGFR to <35 ml/min per 1.73 m2
	Loss	Persistent ARF=complete loss of kidney function (need for dialysis) >4 weeks			Notable differences: (1) Addition of 0.3 mg/dl absolute change in SCr to increase diagnostic sensitivity (2) eGFR criteria removed (3) 48-h time window to ensure acuity (also allows for inpatient baseline values) (4) Exclusion of Loss/ESKD categories as diagnostic criteria		Notable differences: (1) Time frame differences for absolute versus relative changes in serum creatinine (2) 0.5 mg/dl increase for those with SCr ⩾4.0 mg/dl (354 μmol/l) no longer required if minimum AKI threshold met (3) Inclusion of eGFR criteria for children
	ESKD	End-stage kidney disease (>3 months)

Abbreviations: AKI, acute kidney injury; AKIN, Acute Kidney Injury Network; ARF, acute renal failure; eGFR, estimated glomerular filtration rate; ESKD, end-stage kidney disease; ESRD, end-stage renal disease; MDRD, Modification of Diet in Renal Disease; KDIGO, Kidney Disease: Improving Global Outcomes; RIFLE, Risk, Injury, Failure, Loss, and End-stage Kidney Disease; SCr, serum creatinine.