Unifying Concepts

Definition and Stages of Chronic Kidney Disease (CKD)

NKF Definition of Chronic Kidney Disease

  • Kidney damage for three or more months, as defined by structural or functional abnormalities of the kidney, with or without decreased GFR, manifested by pathologic abnormalities or markers of kidney damage, including abnormalities in the composition of the blood or urine or abnormalities in imaging tests

  • GFR < 60 mL per minute per 1.73 m2 for three months or more, with or without kidney damage

NKF Classification of Chronic Kidney Disease

Stage Description† GFR (mL per minute per 1.73 m2) Action plan
At increased risk for chronic kidney disease > 60 (with risk factors for chronic kidney disease) Screening, reduction of risk factors for chronic kidney disease
1 Kidney damage with normal or elevated GFR > 90 Diagnosis and treatment, treatment of comorbid conditions, interventions to slow disease progression, reduction of risk factors for cardiovascular disease
2 Kidney damage with mildly decreased GFR 60 to 89 Estimation of disease progression
3a Mild to Moderately decreased GFR 45 to 59 Evaluation and treatment of disease complications
3b Moderately to severely decreased GFR 30 to 44 Evaluation and treatment of disease complications
4 Severely decreased GFR 15 to 29 Preparation for kidney replacement therapy (dialysis, transplantation)
5 Kidney failure < 15 (or dialysis) Kidney replacement therapy if uremia is present

Risk Factors for Chronic Kidney Disease and Its Outcomes

Type Definition Examples
Susceptibility factors Factors that increase susceptibility to kidney damage Older age, family history of chronic kidney disease, reduction in kidney mass, low birth weight, U.S. racial or ethnic minority status, low income or educational level
Initiation factors Factors that directly initiate kidney damage Diabetes mellitus, high blood pressure, autoimmune diseases, systemic infections, urinary tract infections, urinary stones, obstruction of lower urinary tract, drug toxicity
Progression factors Factors that cause worsening kidney damage and faster decline in kidney function after kidney damage has started Higher level of proteinuria, higher blood pressure level, poor glycemic control in diabetes, smoking
End-stage factors Factors that increase morbidity and mortality in kidney failure Lower dialysis dose (Kt/V)*, temporary vascular access, anemia, low serum albumin level, late referral for dialysis

*-In Kt/V (accepted nomenclature for dialysis dose), “K” represents urea clearance, “t” represents time, and “V” represents volume of distribution for urea.

NKF = National Kidney Foundation; GFR = glomerular filtration rate.



  1. National Kidney Foundation. K/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. Am. J. Kidney Dis. 2002 Feb;39(2 Suppl 1):S1-266. [Medline]


Created: Jul 01, 2007

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