Everything about Kidney Function Tests

Kidney Function Tests

Every person has two kidneys on either side of the spine which are approximately the size of a human fist. They are situated posterior to the abdomen and below the rib cage. Both the kidneys have crucial roles in maintaining your health condition. One of their important jobs is to filter out waste materials from your blood and remove them from the body in the form of urine. Your kidneys help in controlling the levels of water and different necessary minerals in the body. Besides, they are vital in the production of:

  • red blood cells
  • vitamin D
  • hormones that control blood pressure

If the doctor finds your kidneys are not working properly, you may have to conduct kidney function tests. These are simple urine and blood tests that can detect problems with the kidneys. You may require conducting kidney function test when there are other conditions that can cause harm to the kidneys such as high pressure or diabetes. They can help doctors to evaluate these conditions.

Symptoms of kidney problems

Symptoms which denote a problem to the kidneys are:

  • blood in your urine
  • high pressure
  • difficulty in urination
  • painful urination
  • frequent urge to urinate
  • swelling of feet and hands due to the accumualtion of fluids in your body

Having a single symptom might not mean anything serious. But when they happen together, these symptoms denote your kidneys are not working properly. With the help of kidney function test, you will be able to determine the reason.

Types of kidney function tests

In order to test kidney functioning, the doctor orders a set of tests that may evaluate your glomerular filtration rate or GFR. The GFR informs the doctor how soon the kidneys can clear waste away from your body.

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A urinalysis helps to screen whether there is the presence of blood and protein in your urine. There are probable reasons for protein present in the urine and any infection increases your urine protein. The doctor may like to repeat the test after some weeks to find out whether the results are similar.

The doctor may ask to provide 24-hour urine collection sample. This helps the doctors to know how quickly the waste product called creatinine is clearing away from your body. Creatinine is the breakdown product of your muscle tissue.

Serum creatinine test

With this blood test, the doctor determines if creatinine is accumulating in the blood. Your kidneys filter creatinine from blood completely and higher creatinine level denotes a kidney problem. Having a creatinine level more than 1.4 mg/dL for men and 1.2 milligrams/deciliter (mg/dL) for women denotes there is a kidney problem.

Blood urea nitrogen or BUN

The blood urea nitrogen test checks for waste products in the blood. BUN tests evaluate the amount of nitrogen present in your blood. So, urea nitrogen is actually a breakdown protein product. But all BUN tests do not occur due to damage to the kidneys. Common medications are kinds of antibiotics and large aspirin doses which increases blood urea nitrogen. It is necessary to inform the doctor about any supplements or medications that you take daily. You may have to stop certain drugs for a few days before the test. The normal BUN level should be between 7 and 20 mg/dL. But having higher value may denote several health concerns.

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Estimated GFR

The test estimates how properly the kidneys are filtering out the waste. The test determines the rate by considering certain factors, such as:

  • age
  • race
  • gender
  • test results to know creatinine levels
  • weight
  • height

If the result is below 60 milliliters/minute/1.73m2, this can be a warning sign of kidney disease.

How you need to perform the tests

The kidney function tests usually need a 24-hour urine sample and a blood test.

24-hour urine sample – This is a creatinine clearance test which gives the doctor an idea of the amount of creatinine level your body expels in one day. When you start the test, urinate properly as you would when you wake up. For the remaining day and night, urinate in a container given by the doctor. Store your container in the refrigeration at the time of collection process. You need to label the container clearly and tell other family members why it is there in the refrigerator.

On the morning of your second day, urinate into the container when you get up. This will complete 24-hour collection process. Make sure you follow the instructions of your doctor where to drop the sample off. You may have to return it either to the doctor’s office or the laboratory.

Blood samples – Serum creatinine and BUN tests need blood samples to be taken at the doctor’s office. Your blood is taken by tying an elastic band around the upper arm which makes your veins to stand out. The technician cleans the area over your vein and the blood flows back into a test tube to be sent for further evaluation.

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You might feel sharp prick when a needle enters into the arm. The technician places a gauze and bandage over the puncture site after the test. The area around the puncture might develop some bruise over the next few days. But you should not feel pain for a long time.

The doctor will ask to conduct private kidney function test and find out whether both the kidneys are functioning properly.

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