Understanding Glomerular Filtration Rate
Monday, July 07, 2008 Article by: D.K. Mangusan Jr., PTRP
Glomerular filtration rate (GFR) is an estimate or calculation of how well the kidneys are filtering wastes from the blood. The doctor can calculate it from routine measurement of creatinine in the blood. Creatinine is a waste product formed from the normal breakdown of muscles during activity. The healthy kidneys remove creatinine out of the blood and become part of the urine. Creatinine will build up in the blood when the kidneys are not working properly.
Normal GFR may vary according to age, race, and gender. As people get older, the average GFR drops. However, when the GFR number is below 60, it may indicate that some damage to the kidneys has occurred.
The GFR number is an important indicator of how well the kidneys are working. The number is also used to determine a patient’s stage of kidney disease. The doctor will also look at other factors, including:
Protein (albumin) in the urine
Diabetes
High blood pressure or hypertension
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In 2002, the National Kidney Foundation published treatment guidelines that identified five stages of chronic kidney disease (CKD) based on the declining measurements of GFR. The guidelines recommend different actions based on the stage of kidney disease.
Increased risk of CKD.In addition to tracking your GFR, blood tests can show when substances in your blood are out of balance. If phosphorus or potassium levels start to climb, a blood test will prompt your health care provider to address these issues before they permanently affect your health. (National Kidney and Urologic Diseases Information Clearinghouse, August 2007)
A GFR of 90 or above is considered normal. Even with a normal GFR, you may be at increased risk for developing CKD if you have diabetes, high blood pressure, or a family history of kidney disease. The risk increases with age: People over 65 are more than twice as likely to develop CKD as people between the ages of 45 and 65. African Americans also have a higher risk of developing CKD.
Stage 1: Kidney damage with normal GFR (90 or above).
Kidney damage may be detected before the GFR begins to decline. In this first stage of kidney disease, the goals of treatment are to slow the progression of CKD and reduce the risk of heart and blood vessel disease.
Stage 2: Kidney damage with mild decrease in GFR (60 to 89).
When kidney function starts to decline, your health care provider will estimate the progression of your CKD and continue treatment to reduce the risk of other health problems.
Stage 3: Moderate decrease in GFR (30 to 59).
When CKD has advanced to this stage, anemia and bone problems become more common. Work with your health care provider to prevent or treat these complications.
Stage 4: Severe reduction in GFR (15 to 29).
Continue following the treatment for complications of CKD and learn as much as you can about the treatments for kidney failure. Each treatment requires preparation. If you choose hemodialysis, you will need to have a procedure to make a vein in your arm larger and stronger for repeated needle insertions. For peritoneal dialysis, you will need to have a catheter placed in your abdomen. Or you may want to ask family or friends to consider donating a kidney for transplantation.
Stage 5: Kidney failure (GFR less than 15).
When the kidneys do not work well enough to maintain life, you will need dialysis or a kidney transplant.
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You can keep your kidneys healthy no matter what your GFR result is:
Keep your blood pressure controlled below 130/80 mmHg.
Keep your blood sugar and cholesterol levels under control.
Eat healthy and cut back on salt. If you have kidney disease, follow a low protein diet.
Be physically active
Stop smoking
Take medicines the way your doctor tells you to.
Taking steps to prevent or slow progression of kidney disease is very important before a lot of damage is done. If your kidneys fail, dialysis and a kidney transplant are the only options to maintain life. Work with your kidney health care team on the best treatment plan for you.
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Where can I get more information?
National Kidney Foundation
Internet: www.kidney.org
National Kidney Disease Education Program
Internet: http://www.nkdep.nih.gov
National Kidney Disease Information Clearinghouse
Internet: http://kidney.niddk.nih.gov
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References:
National Kidney Disease Education. Explaining GFR: A Tear-off Pad for Clinical Use. National Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD. June 2008. Available at http://www.nkdep.nih.gov/resources/ExplainingGFR.htm. Accessed July 2008.
National Kidney Disease Education. Understanding GFR: A Guide for Patients. National Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD. December 2005. Available at http://www.nkdep.nih.gov/resources/glomerular_filtration_rate.htm. Accessed July 2008.
National Kidney and Urologic Diseases Information Clearinghouse. Your Kidneys and How They Work. National Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD. NIH Publication No. 07–3195, August 2007. Available at http://kidney.niddk.nih.gov/kudiseases/pubs/yourkidneys/index.htm. Accessed July 2008
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