Exams and Tests

Tests for chronic kidney disease are vital to help find out:

• Whether kidney disease happened suddenly or has been happening over a long time.
• What is causing the kidney damage.
• Which treatment is best to help slow kidney damage.
• How well treatment is working.
• When to begin dialysis or have a kidney transplant.

After you are diagnosed with chronic kidney disease, blood and urine tests can help you and your doctor monitor the disease.

Tests to check kidney function

When kidney function is decreased, substances such as urea, creatinine, and certain electrolytes begin to build up in the blood. The following tests measure levels of these substances to show how well your kidneys are working.

• A blood creatinine test helps to estimate the glomerular filtration rate (GFR) by measuring the level of creatinine in your blood. The doctor can use the GFR to regularly check how well the kidneys are working and to stage your kidney disease.
• A blood urea nitrogen (BUN) test measures how much nitrogen from the waste product urea is in your blood. BUN level rises when the kidneys aren't working well enough to remove urea from the blood.
• A fasting blood glucose test is done to measure your blood sugar. High blood sugar levels damage blood vessels in the kidneys.
• Blood tests measure levels of waste products and electrolytes in your blood that should be removed by your kidneys.
• A blood test for parathyroid hormone (PTH) checks the level of PTH, which helps control calcium and phosphorus levels.
• Urinalysis (UA) and a urine test for microalbumin, or other urine tests, can measure protein in your urine. Normally there is little or no protein in urine.

Tests for anemia

If the kidneys don't produce enough of the hormone erythropoietin needed to make red blood cells, anemia can develop. The following tests help monitor anemia:

• A complete blood count (CBC) measures the hematocrit and the hemoglobin level.
• A reticulocyte count shows how many red blood cells are being produced by the bone marrow.
• Iron studies show your level of iron, which is needed for erythropoietin to work the way it should.
• A serum ferritin test measures the protein that binds to iron in your body.

Other tests

Your doctor may use other tests to monitor kidney function or to find out whether another kidney disease or condition is contributing to reduced kidney function.

• An ultrasound of the kidney (renal ultrasound) helps estimate how long you may have had chronic kidney disease. It also checks whether urine flow from the kidneys is blocked. An ultrasound also may help find causes of kidney disease, such as obstruction or polycystic kidney disease.
• A duplex Doppler study or angiogram of the kidney may be done to check for problems caused by restricted blood flow (renal artery stenosis).
• A kidney biopsy may help find out the cause of chronic kidney disease. After a kidney transplant, a doctor may use this test if he or she suspects the organ is being rejected by your body.

Early screening for chronic kidney disease

Experts recommend screening tests for chronic kidney disease in high-risk groups, such as people with diabetes or high blood pressure. Kidney disease runs in families, so close family members may also want to have their kidney function tested. Being diagnosed with kidney disease before it has progressed gives you the best chance to control the disease.

To learn more about screening if you already have diabetes or high blood pressure, see:

• Diabetic Nephropathy.
• High Blood Pressure.