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How Diabetes Impacts Your Kidneys

An interview with Robert C. Stanton, MD, a physician in the Division of Nephrology at Beth Israel Deaconess Medical Center.

What is the function of the kidneys?

Dr. Robert Stanton: Your kidneys perform many important functions, most notably filtering and removing waste and extra fluid from your body. These products are then eliminated from your body through urine.

Your kidneys

  • Remove toxins from the blood
  • Regulate the amount of water, salt, potassium, and acid levels in the blood
  • Activate Vitamin D, keeping bones strong and healthy
  • Produce hormones that regulate blood pressure and stimulate red blood cell function

How does diabetes affect kidneys?

Dr. Robert Stanton: Diabetes through high blood glucose levels primarily affect the inner lining of blood vessels potentially damaging the blood vessel. If blood vessels in the kidney are damaged, kidneys cannot do their jobs properly.

The damage is seen mainly in the filters (which are very small blood vessels) in your kidneys, so they cannot filter your blood properly. Protein can leak out of your body through urine. The higher the amount of protein in the urine, the greater chance for declining kidney function. Also increased protein levels in the urine are associated with worse cardiovascular disease. When kidneys near the point of failure, waste and fluid can also build up in the blood.

Are there any symptoms of diabetic kidney disease?

Dr. Robert Stanton: There are no symptoms in the early stages of diabetic kidney disease.

Symptoms of kidney failure - fatigue, nausea and fluid retention - usually don't occur until the late stages of kidney disease. This is because the kidney can still filter blood adequately and do its other function even after it has been significantly damaged.

What tests can be done to find early kidney disease?

Dr. Robert Stanton: Two tests - one using urine and the other blood - must be performed annually to find early kidney disease.

The urine sample is used to screen for even a small increase in albumin in the urine (called microalbuminuria). This occurs when a protein called albumin starts to leak out of the kidney filters into your urine. It is often the first sign of diabetic kidney disease. The standard urine dipstick used in doctors' offices does not detect this-a special machine is required instead which measures the amount of albumin/creatinine in the urine.

The second test is a blood test that is used to measure your level of creatinine. This substance is normally present in the blood but increases if your kidneys are not functioning properly. The creatinine level is then used to calculate your GFR. Some patients have lower GFR due to diabetes even in the absence of increased urine albumin level. So every year a GFR test (measure serum creatinine and calculate the GFR) and a microalbumin test should be done.

What is GFR?

Dr. Robert Stanton: GFR stands for Glomerular Filtration Rate. It is calculated from your age, race, gender, results of your blood creatinine test and other factors. The two most commonly used formulae are the MDRD equation and the CKD-EPI equation. These formulae are available to anyone and can be found by searching on-line.

Why is GFR so important in determining kidney function?

Dr. Robert Stanton: Creatinine value alone can be misleading. Patients often have more advanced kidney disease than their blood creatinine value alone suggests. The National Kidney Foundation considers GFR the best way to determine kidney function, and recommends that all doctors calculate the GFR and not use creatinine alone.

What can people with diabetes do to prevent future kidney problems?

Dr. Robert Stanton: In addition to screening for kidney disease, there are five important things that everyone with diabetes should do to help prevent kidney disease and to treat kidney problems:

  • Have tight control of blood glucose levels (A1C less than 7 percent).
  • Keep blood pressure lower than 130/80.
  • Ask your doctor about blood pressure-lowering drugs, such as ACE inhibitors or angiotensin receptor blockers (ARBs). These have been shown to be effective in slowing worsening of the kidney from damage if you increased urine albumin levels from diabetic kidney disease.
  • Do not smoke. Smoking is a poison for the inner lining of your blood vessels. The combination of high glucose in your blood and smoking is a very poisonous combination for your blood vessels.
  • Control lipids: LDL ("bad") cholesterol should be less than 100 mg/dl, HDL ("good") cholesterol should be above 50 mg/dl and triglycerides should be less than 150 mg/dl.

Above content provided by Beth Israel Deaconess Medical Center in partnership with the Joslin Diabetes Center. For advice about your medical care, consult your doctor.

Posted November 2012

Contact Information

Division of Nephrology
Department of Medicine
Beth Israel Deaconess Medical Center
West Campus/Farr 8
185 Pilgrim Road
Boston, MA 02215
617.632.9880
617-632-9890