Module 1: Understanding Chronic Kidney Disease (ckd)

Use eGFR to assess and monitor kidney function

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• The eGFR is the estimated glomerular filtration rate.
• The eGFR provides an estimate of how much plasma is filtered by the kidneys each minute.

What is the glomerular filtration rate (GFR)?

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• GFR is equal to the sum of the filtration rates in all of the functioning nephrons.
• GFR is not routinely measured in clinical settings.
• Estimation of the GFR (eGFR), using serum creatinine level, gives a rough measure of the number of functioning nephrons.

What is the GFR?

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• Cardiac output (CO) = 6 L/min
• X 20% of CO goes to kidneys = 1.2 L/min
• X Plasma is 50% blood volume = 600 mL/min
• X Filtration Fraction of 20% = 120 mL/min

eGFR estimates the measured GFR

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• eGFR is not the measured GFR.
• eGFR estimates the measured GFR.
• The eGFR is a good estimate of the risk of having decreased kidney function.
• Like other risk predictors, when it is the solitary indicator, it should be used cautiously, especially when “diagnosing” disease.

Estimating equations for eGFR

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• The Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology (CKD-EPI) equations are most widely used for estimating GFR.
• The variables include serum creatinine (Scr), age, race, and gender.
• MDRD eGFR = 175 x (Scr) -1.154 x (age) -0.203 x (0.742 if female) x (1.212 if African American)
• CKD-EPI eGFR = 141 × min (Scr /κ,1)a × max (Scr /κ,1) -1.209 × 0.993 age × (1.018 if female) × (1.180 if African American)
• The estimate is normalized to body surface area.

• References: Levey et al. Ann Intern Med. 1999; 130:461–470;
• Levey et al. Ann Intern Med. 2009:150:604–612.