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What is Glomerular Filtration Rate (GFR)

  • Posted on- Aug 27, 2015
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If you experience symptoms of kidney disease, your nephrologist will recommend a few tests. One of these tests helps to determine the GFR, or glomerular filtration rate of your kidneys. This refers to the amount of fluid that’s filtered per minute by the glomeruli - capillaries or tiny blood vessels in the kidneys.

The GFR test is considered to be the most accurate way to measure how well your kidneys are functioning. It can also help your nephrologist to determine the stage of your kidney disease. This illness is a progressive disease that has no cure with orthodox therapies. It goes through five stages in which symptoms become worse, or you start to experience additional symptoms. Knowing the stage of the disease you’re in affects your treatment.

How is Glomerular Filtration Rate (GFR) measured?

Previously, GFR was measured through a 24-hour collection of urine to track the filtration rate of a substance injected into the body. These days, an estimate of GFR (eGFR) is done through a blood test. This test measures the levels of creatinine in the blood, without the need for a substance to be injected. Sometimes, the terms GFR test and eGFR tests are used interchangeably.

A health care professional will collect a sample of blood from your vein. Small children being tested for kidney disease may be pricked through the skin with a lancet in order for blood to be collected. The blood sample is sent to a lab for assessment.

As mentioned, nephrologists check for levels of a substance called creatinine. It’s a waste product of muscle metabolism. It’s eliminated from the body by healthy kidneys through urine and remains within a certain range in the body. However, when the kidneys cannot effectively rid your body of creatinine, it accumulates to higher than normal levels, indicating that kidney disease is present.

To determine your GFR, other factors are taken into account, such as your age, race, and gender. Also, GFR is compared to levels of protein in your urine for even greater accuracy to determine the albumin-to-creatinine ratio (UACR). A healthy ratio is 0.2 grams of protein to one gram of creatinine.

Nephrologists may also use a method known as the Cockcroft-Gault formula to estimate creatinine clearance from your blood, and in turn, your GFR. This method uses creatinine measurements and your weight to predict the rate at which creatinine is being removed from the blood.

GFR may need to be measured more than once before an assessment of kidney function is determined.

Although the eGFR is a very useful test to determine kidney function, it’s not useful for everyone with suspected kidney disease as results may vary in some situation. This includes people who are:

  • Age 70 or older
  • Under 18 years old
  • Pregnant
  • Obese or overweight
  • Very muscular
  • Malnourished
  • Vegetarian
  • Of African descent

These factors affect creatinine generation. In these cases, the traditional GFR test with 24-hour urine collection may be more accurate.

What happens if your Glomerular Filtration Rate (GFR) is low?

Your nephrologist will likely recommend other tests such as an ultrasound or CT (computer tomography) scan to spot any abnormalities in the kidneys such as kidney stones. These tests can also determine if there are blockages in your urinary tract, which could also affect how well your kidneys are filtering.

Another test your nephrologist may perform if your GFR is low is a kidney biopsy. During this test the nephrologist will insert a needle into your kidney to remove tissue to examine for abnormalities or disease.

If you are diagnosed with any level of kidney disease, or you are at risk, the use of natural therapies can both reverse damage and prevent future kidney damage by treating the cause of the problem. Herbs, nutrients and dietary and lifestyle changes can go a long way in improving your kidney health and your health in general.