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Ask the Doctor

Millie SamaniegoDr. Milagros (Millie) Samaniego is an Associate Professor and Transplant Physician in the Section of Nephrology at the University of Wisconsin-Madison. She is Associate Editor of the American Journal of Transplantation and is an active member of the American Society of Transplantation, the American Society of Nephrology, and the National Kidney Foundation. For many years she has researched kidney transplant rejection and sensitization issues.

People with diabetes are at increased risk of developing kidney disease. This risk varies with the type of diabetes: Although a higher percentage (50%) of Type 1s will develop kidney disease and failure, Type 2 diabetes has become the most common cause of kidney failure because of the high number of people in the United States with Type 2. Up to a quarter of people with Type 2 diabetes will develop kidney disease, so it’s very important to be aware of this risk and make sure you are getting the testing you need to monitor your kidney function.

Q: Why am I at risk of kidney problems just because of my diabetes?

A: Diabetes damages small and large blood vessels and the kidney is full of those, so it is at increased risk of damage. At the same time diabetes can cause changes in the pressure inside an important capillary network in the kidney called the glomerulus, which is in charge of filtering the poisons in the blood. This is called glomerular hypertension, which causes the kidneys to work harder and affects the filtration rate and causes more kidney damage. So if you have diabetes you must control your blood pressure and make sure you have tests for kidney function every year.

Q: What is the GFR test and why do I need it (do I need it)?

A: The GFR is a check of your glomerular filtration rate (GFR) and is the best reflection of kidney function that we have available. Along with the creatinine level in your blood, your age, race, body size and sex are used in a formula to determine how well your kidneys are filtering waste and extra fluid from your body. If your result is anything below 90 ml per minute, you may have impaired kidney function.

Q: Are there other tests I should be getting to make sure my kidneys are OK?

A: You have probably been getting a standard annual urinalysis to check for blood and protein in the urine, but if you have diabetes you should also have a separate urine test (microalbuminuria) which looks for trace protein called mircoalbumin. If there is microalbumin in your urine and you are diabetic that immediately qualifies you as having kidney disease, regardless of your GFR, so this is a very important test. Your doctor may want to follow up with radiological testing such as ultrasound to look at the size of your kidneys, which are usually each about the size of a fist. If they appear small, the shrinking may indicate that you have had kidney disease for a long time.

Based on these tests your doctor may decide to do a kidney biopsy where a small needle is inserted and tissue is studied under the microscope.

Q: What are the symptoms of kidney disease or failure? Will I be able to tell?

A: It’s a silent disease. That is why it is so important to have the screening tests. By the time you are sent to a nephrologist (kidney doctor) you may already have an advanced form of the disease. If you have undetected kidney disease, you may have swelling of the legs (edema) or hypertension. If you have high blood pressure you should be seeing a nephrologist.

Q: What are the best ways to manage my diabetes and kidney health?

A: The best thing that you can do to stall the onset or progression of kidney disease is make sure your blood pressure is under optimal control. Talk to your doctor about taking an ace inhibitor or angiotensin-2 receptor blocker even if you don’t have high blood pressure (hypertension). Get annual GFR and microalbuminuria tests, and monitor the results carefully. Also, monitor your glycemic control with A1c tests twice a year (every three months if your goal has not been reached), treat high cholesterol, and don’t smoke!