MEASUREMENT OF GLOMERULAR FILTRATION RATE Flashcards
What is GFR?
Rate at which fluid is filtered across the glomerular membrane.
GFR is the best index of kidney function and is used to define and stage Chronic Kidney Disease (CKD).
What is Single Nephron GFR (SNGFR)?
Filtration rate of a single nephron.
SNGFR is a component of the overall GFR.
How is Total GFR calculated?
GFR = N × SNGFR.
N represents the number of nephrons.
What is the ideal filtration marker for measuring GFR?
Inulin.
Inulin is rarely used; alternatives include iohexol and iothalamate.
What is the clearance formula for GFR?
Cl_x = U_x × V / P_x.
This formula is used to calculate clearance based on urine and plasma concentrations.
What are the units for GFR measurement?
mL/min per 1.73 m².
This measurement is adjusted for body surface area (BSA).
How is Creatinine Clearance calculated?
Cl_{cr} = U_{cr} × V / P_{cr}.
Creatinine clearance can overestimate GFR due to tubular secretion.
What is the most accurate equation for estimating GFR from serum creatinine?
CKD-EPI Equation.
This equation is preferred for estimating GFR.
What is the limitation of the Cockcroft-Gault Formula?
It overestimates GFR.
The Cockcroft-Gault formula is less accurate than the CKD-EPI equation.
What is Cystatin C?
An alternative marker for estimating GFR.
Cystatin C is less influenced by muscle mass.
What is the CKD-EPI Cystatin C Equation?
eGFR = 133 × min(SCysC/0.8,1)^{-0.499} × max(SCysC/0.8,1)^{-1.328} × 0.996^{Age} × 0.932 [if female].
This equation is used for estimating GFR based on Cystatin C levels.
What does eGFRcr-cys represent?
The most accurate estimation when both creatinine and cystatin C are used.
It combines the strengths of both markers for a more accurate GFR estimate.
What is the recommendation for estimating GFR in pediatric populations?
Use height-inclusive equations like the updated Schwartz formula.
Pediatric equations account for growth and development.
True or False: Estimating equations are accurate in rapidly changing kidney function.
False.
In such cases, kinetic equations should be used instead.
What factors can affect serum creatinine levels?
Muscle mass, diet, and tubular secretion.
These factors can lead to inaccuracies in GFR estimation.
What does the FDA recommend for drug dosing adjustments?
Use the most accurate GFR estimation method.
Accurate GFR estimates are crucial for safe drug dosing.
List key points regarding GFR.
- GFR is the best index of kidney function.
- Normal GFR varies by age, sex, and body size.
- CKD-EPI equation is the most accurate for estimating GFR.
- Cystatin C is an alternative marker with different determinants.
- Online calculators are available for eGFR computation.
- Confirmatory tests are recommended for accurate GFR estimation.
- Estimating equations are inaccurate in rapidly changing kidney function.
