Table 1.

Definitions, Stages and Burden of Kidney Disease^*

	Acute Kidney Injury (AKI)	Acute Kidney Diseases and Disorders (AKD)	Chronic Kidney Disease (CKD)
Duration	Within 2-7 days	≤ 3 months	> 3 months
Functional Criterion	Rise in serum creatinine by 50% (7days) OR Rise in serum ceatinine by 0.3 mg/dl (26.5 micromol/l) (2 days) OR Urine output <0.5 for 6 hours	GFR <60 ml/min/1.73 m2 OR Decline in GFR by >35% times baseline OR Rise in serum creatinine by >50% times baseline	GFR <60 ml/min/1.73 m2
Structural Criterion	None required	Marker of kidney damage (hematuria or pyuria are most common)	Marker of kidney damage (albuminuria is most common)
Examples**	Decreased kidney perfusion (“pre-renal disorders”) Urinary tract obstruction (“post-renal” disorders) Intrinsic kidney diseases (acute tubular necrosis, acute interstitial nephritis)	Acute and rapidly progressive glomerulonephritis Acute presentations of nephrotic syndrome Acute pyelonephritis Partial obstruction of the urinary tract	Diabetic kidney disease Hypertensive nephrosclerosis Chronic glomerulonephritis Chronic interstitial nephritis Chronic pyelonephritis Polycystic kidney disease Chronic heart failure Chronic liver disease
Staging	Serum creatinine (mg/dl) and urine output (ml/kg/h) categories: Stage 1: serum creatinine rise by ≥0.3 from baseline OR serum creatinine rise by 1.5 to1.9 times baseline OR urine output <0.5 for 6-12 hours. Stage 2: serum creatinine rise by 2.0 to 2.9 times baseline OR urine output <0.5 for ≥12 hours. Stage 3: serum creatinine rise by ≥ 3.0 times baseline OR serum creatinine ≥ 4 OR renal replacement therapy	Not defined	Albuminuria categories (ACR mg/g approximately equivalent to AER mg/d) and related terms: A1: <30, normal to mildly increased A2: 30-300, moderately increased (formerly “microalbuminuria”) A3: >300, severely increased (includes nephrotic syndrome, >~ 2000) GFR categories (ml/min/1.73 m2) and related terms: G1: >90, normal or high G2: 60-89, mildly decreased G3a: 45-59, mildly to moderately decreased G3b: 40-44, moderately to severely decreased G4: 15-29, severely decreased G5:<15 OR treated by dialysis, kidney failure
Burden	Incidence 10-20 % among adults requiring hospitalization (0.3% requiring dialysis)	Unknown	Prevalence ~ 10% in non-hospitalized adults (higher in the elderly) Life time risk ~ 50% Prevalence of kidney failure treated by dialysis or transplantation ~0.3% (higher in the elderly) Life time risk of kidney failure 2-8% (higher in blacks)

^*GFR, glomerular filtration rate; ACR, albumin-to-creatinine ratio; AER, albumin excretion rate. Rise in serum creatinine of 0.3 mg/dl is equivalent to 26.5 micromol/l. ACR of 30, 300 and 2000 mg/g are approximately equivalent to 3, 30 and 200 mg/mol, respectively. Modified from Eckardt KU, Coresh J, Devuyst O, et al. Evolving importance of kidney disease: from subspecialty to global health burden. Lancet. Jul 13 2013; 382(9887):158-169.³

^**Additional diagnostic testing is required to determine the cause of disease and treatment.