Kidney Function Test – The Facts

The kidneys are organs that filter toxins from the blood and ensure that it maintains the correct balance of fluids and nutrients. Almost every person has two of these organs but it is possible to live a healthy life with only one kidney. The kidneys are located just below the ribs around the lower middle portion of the back. Every single day the kidneys will process around 180 litres blood, and will usually excrete around 1 litre of waste. This waste is passed through the ureters and on to the bladder, where it is eliminated as urine. There is many a kidney function test that can keep an eye on this process if any kidney disease is suspected.

When the body takes the nutrients from the food you eat, it sends all the waste into the blood stream. If the kidneys do not filter the blood, it would just accumulate all the waste and end up damaging the body. In the medical field, professionals refer to kidney function as renal function. The use of a kidney function test allows a medical provider to know how efficiently the kidneys are operating. 100% function is the healthiest state for the kidneys to be in, although a decline of up to 40% is barely noticeable, and the kidneys are still able to effectively remove waste from the blood in this state.

Doctors use a test called an eGFR, or estimated glomerular filtration rate to calculate renal function. A blood sample is used, making this procedure a more accurate kidney function test. A greatly reduced renal function of 25% or less can indicate a very serious kidney condition. Once renal function falls below 15%, the patient must either undergo dialysis, which is an artificial filtering of the blood, or they must receive a kidney transplant.

The problem with kidney disease is that often it will not manifest any symptoms initially. Once symptoms do appear the damage to the kidneys can be quite advanced. Because of this, doctors need to come across the condition through regular urine and blood tests to discover the problem early. Doctors recommend that people regularly undergo a kidney function test to indicate the presence of damage; there are three common types:

Kidney Function Test #1 – Blood pressure test: Elevated blood pressure can be one of the contributing factors of kidney disease. It may also indicate that the kidneys are impaired in some way already. Blood pressure should ideally be at or below 120/80, and if it isn’t certain lifestyle changes and medication may be necessary.

Kidney Function Test #2 – Urine is checked for albumin or protein: Normally the filtration process will leave protein in the blood while other chemicals are filtered out. With impaired renal function, the kidneys may begin to filter a form of protein that they shouldn’t, called albumin. A doctor can easily perform an albumin check with a urine sample.

Kidney Function Test #3 – eGFR test: The estimated Glomerular Filtration Rate is one the more widely used kidney function test. It measures the amount of creatinine in the blood, specifically measured in milligrams per deciliter of blood. The GFR also takes into account factors such as a patient’s age and gender. A GFR test consists of an injection, followed by a urine sample 24 hours later, to detect how much of the test chemical has managed to pass through the kidneys.

As you can see the kidneys are essential organs to life. It is easy to detect early kidney damage with the use a kidney function test so that treatment can be introduced early to prevent further damage to the kidneys.


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The Importance Of An eGFR Kidney Function Test

The purpose of the eGFR test is to screen for kidney damage and decreased kidney function and it is used to detect the early stages of disease development. Mainly, eGRF is assessed with the use of a creatinine test. Doctors frequently order this kidney function test when they wish to create an evaluation of kidney disease. It can be used both to test for suspected kidney damage and to monitor patients with a previously diagnosed kidney disease. It can also be ordered for patients with hypertension and diabetes, as both of these conditions that can accelerate damage to the kidneys.

Generally the eGFR test is ordered when symptoms of kidney malfunction are present in a patient. The eGFR can easily be determined whenever a blood sample is tested for creatinine levels. The National Kidney Foundation recommends an eGFR calculation with every creatinine test performed. This kidney function test can be ordered whenever a doctor determines that a patient’s kidney function requires evaluation, whether it is part of a routine checkup or the doctor suspects a form of kidney disease to be present in the patient.

Early symptoms of renal disease can include, but are not limited to:

  • Swelling in the ankles, thighs, wrists, face, abdomen, or around the eyes
  • Bloody or foamy urine
  • Decreased urine volume
  • Difficulty urinating.
  • Burning sensation or unusual discharge during urination. This can be seen alongside either an increase or decrease in urination frequency
  • Pain where the kidneys are situated, which is the lower back just under the ribcage
  • Hypertension or elevated blood pressure

As the disease gets worse another kidney function test may be warranted if symptoms include:

  • More fluctuation in urinating frequency, such as urinating less or more often
  • Itchy skin in any part of the body
  • Fatigue, difficulty concentrating and exhaustion
  • Low appetite, often accompanied by nausea or vomiting
  • Numbness or swelling in the feet and hands
  • Patches of dark skin pigmentation
  • Muscle cramps

An eGFR test is one very reliable kidney function test for detecting renal disease than a creatinine test by itself. A test result of less than 60 ml/min is indicative of damage to the kidneys.

The levels of creatinine can vary as a response to protein consumption and by the mass of muscle tissue in an individual. Men will generally have higher levels of creatinine than children and women. Pregnant women tend to have a higher GFR as well.

Make sure you get your eGFR kidney function test regularly to track the progression of your condition.


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What Is The Best Kidney Function Test To Take?

When testing renal function in patients either with or without a history of kidney disease, doctors will typically order a kidney function test, sometimes several at the same time to give them an accurate view of the function of the kidneys. GFR and creatinine tests are the most widely used by medical practitioners around the world.

The GFR test, or Glomerular Filtration Rate is considered to be the most accurate kidney function test. It calculates the rate at which fluid flows through and is filtered by the kidneys. The creatinine clearance rate test is calculated by how much creatinine is filtered out into the urine by the kidneys per time unit. The figures obtained are very important for assessing current kidney function in a patient.

A kidney function test is used to determine renal function based on calculations in concentrations of certain waste products in the blood, namely urea and creatinine, although electrolytes are often used as well. The problem with the use of a kidney function test isn’t necessarily accuracy, but more relevance to the condition or stage of kidney damage. For example testing for blood urea nitrogen will not show an elevation in the blood stream until the kidneys lose approximately 60% of their function. This makes this test useful for monitoring the advanced stages of kidney disease, but it is inaccurate during the earlier stages. This is why most doctors will tend to go with a glomerular filtration rate test in healthier patients who have only a few of the underlying symptoms of kidney disease.

GFR is the rate at which the glomerular capillaries of the kidneys filter fluids and toxins from the blood. This is a very common kidney function test that measures the ratio of volume to time unit. The GFR can be calculated through the measurement of a chemical in the blood. The chemical used must meet several requirements and have the right traits to be considered useful for testing purposes. It must have either a pre-measured or fairly steady concentration in the blood, and should be filtered freely by the kidneys but be unable to be reabsorbed following filtration. To calculate the GFR, the volume of the chemical in question that is present in a urine sample taken after a specific period of time must be taken into account.

Most of the time, the GFR will be calculated using an injection of inulin into the blood stream. This provides a more reliable kidney function test result, because the original concentration does not have to be estimated. Inulin is safe and meets all the requirements for any chemical used to test GFR, which makes it ideal for the job.


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Kidney Function Test: BUN Test Assesses Kidney Function Accurately

Renal disease is a serious condition that affects the kidneys. The GFR test is the most commonly used calculator of kidney function, but many doctors and laboratories will also order a BUN test as an accurate kidney function test. A BUN, or Blood Urea Nitrogen test is used to help a doctor evaluate the function of the kidneys, diagnose a possible kidney disease and to monitor kidney function in patients with a history of kidney malfunction or failure. Many doctors will also order this test as a complement to a routine health check up. Testing BUN requires only a blood sample and there is no preparation required for the procedure.

This kidney function test measures the concentration of nitrogen in the blood, which is in the form urea. Urea is secreted into the blood from where it is formed in the liver, and the kidneys then filter it out of the body. The BUN test is an excellent method of measuring renal function. An increase in BUN levels means that the kidneys aren’t filtering out as much of the urea nitrogen as it should, and this is indicative of impaired kidney function. A decrease in kidney function can be caused by either chronic or acute kidney damage. Reduced kidney function can be caused by other factors as well, such as diseases or conditions that indirectly affect the kidneys. Some of these conditions decrease the flow of blood that passes through the kidneys, such as a recent heart attack, stress, congestive heart failure, shock or burns.

Another potential cause for BUN levels to be elevated is an increase of protein into the diet. In this case levels are not necessarily indicative of kidney issues, so doctors should always question a patient about their diet and any recent changes that may have been made. However, in general a high protein diet is not recommended for kidney disease patients. Lower than average BUN levels are not usually indicative of a problem with the kidneys, although they can be seen in patients with malnutrition and liver disease. Bun tests are rarely used as a form of monitoring when these conditions are present. If you are pregnant, you can expect a wide variation in BUN levels, so doctors tend to test pregnant patients with different tests to assess kidney function. One of the main issues with the BUN test is that if one kidney is severely malfunctioning while the other one continues to operate at peak efficiency the BUN levels may still remain relatively normal. Other kidney function tests are usually used in conjunction with the BUN test to give doctors a more rounded view of kidney function.

When should you request a kidney function test (BUN test) from your doctor? Some of the signs of decreased kidney function include trouble sleeping, poor appetite, fatigue, high blood pressure and difficulty urinating. Pain in the lower back below the ribcage may also be present in a patient with decreased kidney function. If you are about to undergo a new drug treatment your doctor may order a kidney function test (BUN test) to keep an eye on the condition of your kidneys.


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