Answer. We usually find out that someone has kidney disease from blood tests that show the kidneys are not filtering waste products from the blood stream normally. Two of the waste products are the blood urea nitrogen concentration, often referred to by the initials B.U.N., and the creatinine concentration. Sometimes kidney disease is discovered by finding blood or protein in the urine.             

There are many different causes of chronic kidney disease. Once the doctor finds out that you have kidney disease, she or he will ask you many questions about your health, do a careful physical examination and order blood and urine tests to find out what kind of kidney disease you have and just how well your kidneys are working. The blood tests will also tell whether you are anemic and how well your other organs, like your liver, are functioning. Some blood tests are for specific kinds of kidney diseases, diseases that may effect other parts of your body, and sugar diabetes will also be done. The urine tests will look for protein, blood cells and infection in your urine. You may be asked to collect all of your urine for 24 hours in order to measure how well your kidneys are filtering waste products and how much protein they are losing.             

The doctor will want to find out how big your kidneys are and whether there are any cysts or tumors. To do that an ultrasound test is often done. For this test, a microphone is placed on your back and sound waves are bounced off your kidneys. The ultrasound will also tell if your kidneys are draining urine into your bladder properly. Sometimes special x-rays, like a CT scan, are done to see the kidneys even better.           

Once all these tests are completed, a kidney biopsy may be necessary to tell what kind of kidney disease you have. This test is very important, because different diseases require different medicines. The biopsy is usually done at the hospital as an outpatient, or you may have to stay overnight. After numbing the skin on the back, a needle is placed into the kidney and a small piece of the kidney is removed through the needle to look at under the microscope. It usually takes a few days to get the results and some of the tests may take a week or longer. From all these tests, your doctor may be able to tell you what specific kidney disease you have, how it has affected your kidneys’ ability to filter out waste products and what medications might help treat it.  

Answer provided by George Aronoff, MD, FACP. Dr. Aronoff is Professor of Medicine and Pharmacology and Chief, Division of Nephrology at the University of Louisville School of Medicine, Louisville, Kentucky. He is also a member of the AAKP Medical Advisory Board.

The American Association of Kidney Patients presents Ask the Doctor, an opportunity for readers to submit kidney related health questions to healthcare professionals who specialize in an area of concern. The answers are not to be construed as a diagnosis and therefore, alterations in current healthcare should not occur until the patient’s physician is consulted.

This article originally appeared in the December 2003 issue of Kidney Beginnings: The Magazine, Vol. 2, No. 4.

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