What does the glomerular filtration depend on?

Glomerular Filtration Rate

Abbreviation: GFR
English: glomerular filtration rate

1 definition

The glomerular filtration rate, short GFR, is the volume filtered by the glomeruli of the kidneys per unit of time. It is usually given in the unit ml / min and is one of the most important parameters for assessing kidney function.

2 background

The glomerular filtration rate can be determined by determining the clearance of inulin or creatinine. In addition to the plasma creatinine or inulin concentration, this also requires the amount of urine excreted and the concentration of creatinine or inulin in the 24-hour urine. To save urine collection time, you can determine the eGFR.

3 physiology

The glomerular filtration rate depends on the effective filtration pressure, the total area and the conductivity of the glomerular filter. However, the glomerular filtration rate is not a constant variable. Depending on the time of day, the GFR can fluctuate by up to a third.

Age also has an influence on the glomerular filtration rate. The peak is reached at the end of growth at around 20 years of age. It decreases from the age of 35. However, the glomerular filtration rate must first drop by half before the retention values ​​increase.

Within the age groups, there are variations in the glomerular filtration rate due to different body size and weight, so that it does not seem sensible to memorize different numerical values ​​for different age groups. As a comparison value, the assumption of a glomerular filtration rate of 120 ml / min or 180 l / day in a 20-year-old healthy test person can be used.

see also: glomerular filtration

4 clinic

The most common reason for a permanent decrease in the glomerular filtration rate is renal insufficiency.

5 GFR calculation

To estimate the GFR, a number of approximate formulas were developed that calculate the so-called eGFR from a changing number of parameters (including serum creatinine, body weight, body size, gender, skin color).

5.1 Formulas for adults

5.2 Formulas for children

6 interpretation

According to the recommendations of the Kidney Disease Outcome Quality Initiative (KDOQI), kidney performance is divided into the following stages:

stage description GFR [ml / min / 1.73 m2]
1 Normal or increased GFR > 90
2 Kidney damage, slightly decreased GFR 60 - 89
3 Kidney damage, moderately decreased GFR 30 - 59
4 Kidney damage, severely decreased GFR 15 - 29
5Renal failure < 15

The glomerular filtration rate decreases with increasing age. A healthy kidney loses around 0.7% to 1% of its kidney function annually from the age of 20.

Age [years] Mean GFR
20–29 116 ml / min
30–39 107 ml / min
40–49 99 ml / min
50–59 93 ml / min
60–69 85 ml / min
> 70 75 ml / min