Glomerular filtration rate (GFR) is the volume of fluid filtered from the renal glomerular capillaries into the Bowman's capsule per unit time. Clinically, this is often measured to determine renal function.

The GFR was originally determined by injecting inulin (not insulin) into the plasma. Since inulin is not reabsorbed by the kidney after glomerular filtration, its rate of excretion is directly proportional to the rate of filtration of water and solutes across the glomerular filter. In clinical practice however, creatinine clearance is used to measure GFR. Creatinine is an endogenous molecule, synthesized in the body, which is freely filtered by the glomerulus (but also secreted by the renal tubules in very small amounts). Creatinine clearance is therefore a close approximation of the GFR. The GFR is typically recorded in milliliters per minute (ml/min).

Example: A person has an plasma creatinine concentration of 0.01 mg/ml and in 1 hour he excretes 75 mg of creatinine in the urine. The GFR is calculated as M/P (where M is the mass of creatinine excreted per unit time and P is the plasma concentration of creatinine).

$\backslash mbox\{GFR\; \}=\; \backslash frac\{\backslash frac\{75\backslash mbox\{\; mg\}\}\{60\backslash mbox\{\; mins\}\}\}\{0.01\backslash mbox\{\; mg\}/\backslash mbox\{ml\}\}\; =\; 125\; \backslash mbox\{\; ml\}/\backslash mbox\{min\}$

The Crockroft-Gault formula also estimates Estimated creatnine clearance, which in turn estimates GFT

$\backslash mbox\{Creatinine\; Clearance\; for\; person\; \}P=\; \backslash frac\; \{(140-\backslash mbox\{age\})(\backslash mbox\{ideal\; weight\})\}\; \{72\; \backslash cdot\; P\_\{\backslash mbox\{cr\}\}\}\; \backslash cdot\; f(P)$ where
Body weight in kg
Plasma Creatnine in mg/dL

If ideal body weight is greater than actual body weight, use actual body weight.

The normal range of GFR for males and females is:

• Males: 97 to 137 ml/min.
• Females: 88 to 128 ml/min.

See also

• Renal failure
• Dialysis

External links

• Glomerular Filtration Rate - FP Notebook.
• Learn about your GFR and other lab values - US Kidney Foundation.
• Creatinine clearance - The normal ranges of GFR.
• GFR Calculator Crockroft-Gault - GFR calculation (Crockroft-Gault formula)
• GFR Calculator Jeliffe - GFR calculation (Jeliffe formula)

• eGFR-calculator - A calculator to estimate eGFR

Nephrology

Glomeruläre Filtrationsrate | GFR