If you have symptoms indicating that your kidneys may not work properly, a doctor may prescribe a Kidney Function Test. These common kidney function tests can help find problems early, so treatment can be started quickly to stop disease progression.
A kidney function test is a set of blood and urine tests that your doctor uses to measure your kidneys’ ability to filter wastes from the blood. Your doctor will also check your glomerular filtration rate (GFR).
Blood Test
A blood test is a vital part of diagnosing kidney disease and monitoring the progress of your treatment plan. This non-invasive, painless procedure can help your doctor determine the best course of action for your health.
A small sample of your blood will be taken from a vein in your arm. This will then be sent to a laboratory for analysis. Once the results are available, you will see them on your lab report.
There are several types of blood tests to check kidney function, and your results will tell you whether or not your kidneys are functioning properly. Some of these tests include serum creatinine, blood urea nitrogen, and estimated glomerular filtration rate (eGFR).
Serum creatinine: This test measures the amount of creatinine in your blood. Creatinine is a waste product your body creates during muscle activity and is filtered out by your kidneys.
It is important to understand that your creatinine level should be relatively stable, indicating good kidney function. However, your levels may increase over time if your kidneys are not working as well as they should.
You also need to understand that the ranges for a normal value vary from lab to lab, so you will need to check your report to see which reference ranges were used to calculate your results.
The eGFR: Estimated glomerular filtration rate measures how quickly your kidneys remove waste from your blood. This is a more accurate way to measure kidney function than serum creatinine because it considers factors such as age, body size, gender, and ethnicity.
Urinalysis
A urinalysis is a medical test that checks how well your kidneys work. It uses several different tests to examine your urine and detect any health problems that may be present.
A doctor may suggest a urinalysis as part of your regular medical checkup or as a precautionary measure. It can detect urinary tract infections (UTIs), high blood pressure, or other conditions that may cause kidney or bladder problems.
The urinalysis tests your urine visually and chemically using a dipstick or test strip. A healthcare professional analyzes the test results in a laboratory to identify possible problems.
Your urine will be examined visually for color and clarity. Urine that is cloudy or red may be a sign of infection. Foamy or white urine may indicate an underlying kidney disorder, such as kidney disease or a bladder stone.
Urine samples will also be examined with a microscopic exam, which looks for things the naked eye cannot see. These include red blood cells (erythrocytes), white blood cells (leukocytes), or bacteria (germs).
Other signs that may be detected in the urinalysis are crystals, which can form from chemicals in your urine and become kidney stones. Casts, tube-shaped proteins that may form in your kidneys, can signify kidney disease.
If you have a large amount of protein in your urine, it’s called proteinuria. Many factors, such as strenuous exercise, dehydration, stress, pregnancy, and other conditions, can cause it. But if it stays high over time, this is a sign of kidney disease. Your provider may recommend other urinalysis tests to see how your protein levels change.
Creatinine Test
When doctors want to know how well your kidneys are working, they may use a creatinine test. This test measures the creatinine level in your blood (serum) and urine. It is used to diagnose and monitor kidney disease and other conditions.
The test also helps measure how fast your kidneys filter waste out of your body. Your kidneys move the liquid part of blood through tiny filters called glomeruli and then send waste products out in your urine. The rate at which your kidneys filter your blood is called your glomerular filtration rate, or GFR.
Under normal conditions, your kidneys filter a steady amount of fluid and waste from your blood. That is why serum creatinine levels should be relatively stable. However, if you have kidney problems, your creatinine level can rise quickly.
The creatinine test is a common and safe way to measure how well your kidneys work. It is often ordered when your doctor suspects you have kidney disease or other health problems.
Imaging Test
The imaging test — also called a renal or nuclear medicine scan — uses radioactive materials to take pictures of your kidneys. These images help your doctor evaluate how well your kidneys are working. They can help identify kidney problems or diseases, such as kidney stones, enlarged kidneys, and cysts. These tests can also find blockages in the blood vessels that supply your kidneys.
A kidney biopsy can be done if the kidney function test shows that you have kidney disease. A small sample of your kidney tissue is taken and examined under a microscope for signs of damage. This can also be done if you have other tests that look for abnormal kidney function.