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



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


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


Kidney damage with mildly decreased GFR

60 to 89

Estimation of disease progression


Moderately decreased GFR

30 to 59

Evaluation and treatment of disease complications


Severely decreased GFR

15 to 29

Preparation for kidney replacement therapy (dialysis, transplantation)


Kidney failure

< 15 (or dialysis)

Kidney replacement therapy if uremia is present

Risk Factors for Chronic Kidney Disease and Its Outcomes




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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