The kidneys play several vital roles in maintaining good health. One of their most important jobs is to filter waste materials from the blood and expel them from the body as urine. The kidneys also help control the levels of water and various essential minerals in the body.
There is also need kidney function testing done if you have other conditions that can harm the kidneys, such as diabetes or high blood pressure.
Healthy kidneys remove wastes and excess fluid from the blood. Blood and urine tests show how well the kidneys are doing their job. Urine tests can show how quickly body wastes are being removed and whether the kidneys are leaking abnormal amounts of protein.
- Blood Tests
- Serum Creatinine
Creatinine is a waste product that comes from the normal wear and tear on muscles of the body. This blood test examines whether creatinine is building up in your blood. The kidneys usually completely filter creatinine from the blood. A high level of creatinine suggests a kidney problem. Creatinine levels in the blood can vary depending on age, race and body size. In many labs the normal range is 0.6 to 1.2 mg/dl. Higher levels may be a sign that the kidneys are not working properly. As kidney disease progresses, the level of creatinine in the blood increases.
- Blood Urea Nitrogen (BUN)
Urea nitrogen is produced from the breakdown of food protein. A normal BUN level is between 7 and 20 mg/dl. As kidney function decreases, the BUN level increases.
- Estimated Glomerular Filtration Rate (GFR)
This test estimates how well your kidneys are filtering waste. The test determines the rate by looking at factors, such as:
- test results, specifically creatinine levels
- age
- gender
- race
- height
- weight
Normal GFR can vary according to age (as you get older it can decrease). The normal value for GFR is 90 or above. A GFR below 60 is a sign that the kidneys are not working properly. A GFR below 15 indicates that a treatment for kidney failure, such as dialysis or a kidney transplant, will be needed.
- Urine Tests
Some urine tests require only a few ounces of urine. But some tests require collection of all urine produced for a full 24 hours. A 24-hour urine test shows how much urine your kidneys produce in 1 day. The test also can give an accurate measurement of how much protein leaks from the kidney into the urine in 1 day.
- Urinalysis
Includes microscopic examination of a urine sample as well as a dipstick test. The dipstick is a chemically treated strip, which is dipped into a urine sample. The strip changes color in the presence of abnormalities such as an excess amount of protein, blood, pus, bacteria and sugar. A urinalysis can help to detect a variety of kidney and urinary tract disorders, including chronic kidney disease, diabetes, bladder infections and kidney stones.
A urinalysis screens for the presence of protein and blood in the urine. There are many possible reasons for protein in your urine, not all of which are related to disease. Infection increases urine protein, but so does a heavy physical workout. Your doctor may want to repeat this test after a few weeks to see if the results are similar.
- Creatinine Clearance
A creatinine clearance test compares the creatinine in a 24-hour sample of urine to the creatinine level in the blood, to show how many milliliters of blood the kidneys are filtering out each minute (ml/min).
- Imaging Tests
- Ultrasound
This test uses sound waves to get a picture of the kidney. It may be used to look for abnormalities in size or position of the kidneys or for obstructions such as stones or tumors.
- CT scan
This imaging technique uses contrast dye to picture the kidneys. It may also be used to look for structural abnormalities and the presence of obstructions.
- Kidney Biopsy
A biopsy may be done occasionally for one of the following reasons:
- to identify a specific disease process and determine whether it will respond to treatment
- to evaluate the amount of damage that has occurred in the kidney
- to find out why a kidney transplant may not be doing well
A kidney biopsy is performed by using a thin needle with a sharp cutting edge to slice small pieces of kidney tissue for examination under a microscope.
