Kidney Function Test
Understanding Kidney Function Test
What is Kidney Function Test?
Kidneys play an important role in the removal of waste products and maintenance of water and electrolyte balance in the body. Kidney Function Test (KFT) includes a group of blood tests to determine how well the kidneys are working. It is advised in case of symptoms suggestive of kidney problems such as puffiness around eyes, bloody or foamy urine, frequent urge to urinate etc.
This test is usually a part of routine health checkups. It helps to diagnose kidney related disorders as well as monitor the treatment efficacy of kidney diseases.
What is Kidney Function Test used for?
The Kidney Function Test is performed:
· As a part of routine health checkups
· To help diagnose any disease affecting the kidneys
· To screen people at risk for the development of any kidney diseases
· To monitor treatment efficacy of kidney diseases
What does Kidney Function Test measure?
Contains 3 tests
The kidneys are a pair of bean-shaped organs located on either side of the spinal column in the abdomen towards the back. The kidneys perform a number of important functions. The most important of these is that they filter the blood and separate the waste products generated out of regular metabolic activities of the body, primarily urea. Following the separation, the kidneys excrete the waste products out of the body through urine. They help in maintaining the normal pH level and water balance of the body. The kidneys also play essential roles in the synthesis of Vitamin D and Red Blood Cells (RBCs).
The Kidney Function Test includes the following tests to monitor kidney function:
· Blood Urea Nitrogen (BUN)/ Urea:
Blood Urea Nitrogen is a test to measure the amount of urea nitrogen present in the blood. Urea is a nitrogenous by-product of the metabolism of protein, and its level in blood serves as an indication of the amount of nitrogen present in blood as urea. In simpler terms, BUN is the measure of the amount of nitrogen present in blood in the form of urea. High BUN levels in the blood can be caused as a result of kidney diseases, dehydration and obstruction in the urinary tract due to kidney stones, prostate gland enlargement, etc.
Urea test measures the level of urea in the blood. Urea is a final waste product formed from the breakdown of proteins. Urea is filtered out of the blood by the kidneys to excrete excess nitrogen present in the blood through urine. Excess of urea in blood is called uremia and can be caused by a number of conditions including kidney diseases.
· Uric Acid:
This test measures the level of uric acid in the blood. Uric acid is a waste product formed from the breakdown of purines, which are essential building blocks of DNA. It is also produced by the metabolism of proteinaceous food, especially red meat. Uric acid is excreted from the body by the kidneys through urine and a small portion through stool. The uric acid test indicates the level of uric acid in the blood and serves as an indirect estimation of the proper functioning of the kidneys.
The presence of excess amounts of uric acid in the blood is called hyperuricemia, and causes gout due to the accumulation of uric acid crystals in the synovial fluid between joints. Hyperuricemia also causes the formation of hard lumps of uric acid crystals called tophi under the skin and at the top of the ears. Uric acid crystals can also accumulate in the kidneys and cause kidney stones.
· Creatinine:
This test measures the level of Creatinine in blood. Creatinine is a waste product formed from the normal breakdown of muscles in the body. Creatinine is almost completely excreted by the kidneys, so their levels in the blood serve as an indication of kidney function.
Excess creatinine in the blood can be found due to decreased elimination from the kidneys as well as due to increased creatinine production by muscular breakdown, eating cooked meat, protein supplements, etc.
· BUN/Creatinine Ratio:
BUN/Creatinine Ratio compares the levels of nitrogen as urea in blood to the levels of creatinine in the blood. This ratio serves as a more accurate representation of kidney function. It is also used to check for dehydration since the BUN level increases in dehydration while creatinine levels remain the same. Low BUN to creatinine ratio can be caused due to a low protein diet, liver cirrhosis, rhabdomyolysis (muscle disease), syndrome of inappropriate antidiuretic hormone secretion (SIADH) as well as during pregnancy.
Blood Urea Nitrogen (BUN)
The Blood Urea Nitrogen test measures the amount of urea nitrogen in the blood. Urea is a waste product which is formed in the liver. It is formed when protein is metabolized into amino acids. This leads to the production of ammonia which is further converted into urea which is a less toxic waste product.
Both ammonia and urea have nitrogen as their component. The liver releases urea into the blood which is then carried out to the kidneys. Here, it is filtered out of the blood and then released into the urine. Since this is a continuous process, a small and stable amount of urea nitrogen always remains in the blood.
In case of kidney or liver diseases, there is a change in the amount of urea present in the blood. If the liver produces urea in increased amounts or if there is any problem in the functioning of the kidneys, there can be difficulty in filtering out wastes of the blood which will lead to rising in urea concentrations in the blood. If due to liver damage or disease there is less production of urea, the concentration of BUN will fall.
The BUN test is done along with creatinine test to evaluate kidney function to diagnose kidney disease and to monitor patients undergoing treatment of kidney disease.
Know more about Blood Urea Nitrogen (BUN)
Creatinine
Creatinine is a waste product which is produced by the muscles due to the breakdown of a compound called Creatine. During the cycle of energy production which is required to contract muscles, creatine is produced. Kidneys remove creatinine from the body by filtering it from the blood and then releasing it into the urine. This test measures the amount of creatinine in the blood.
The body produces creatine and creatinine at a relatively same rate. Since kidneys filter most of the creatinine from the blood and release it into the urine, the blood levels can be used as an indicator to know how well the kidneys are functioning. The amount of creatinine produced depends upon the size of the person as well as their muscle mass. That is why levels of creatinine are higher in men as compared to women and children.
Know more about Creatinine
Uric Acid
The Uric acid test measures the levels of uric acid in the blood. Uric acid is a nitrogenous compound produced by the metabolic breakdown of purine. Purines are nitrogenous bases in DNA forming parts of the structural framework of the cells. Breakdown of purines occurs when cells become old and die, forming uric acid. Uric acid is also formed from the metabolic breakdown of some types of food like red meat, seafood, beans, etc.
Most of the uric acid in the blood is filtered and eliminated by the kidneys and a small remaining amount in the stool. The concentration of uric acid in the blood can increase due to overproduction of uric acid or improper elimination of uric acid, and this condition is called Hyperuricemia. Hyperuricemia can also be caused due to cancer treatment by chemotherapy or radiotherapy. These treatment methods kill the cancer cells, which may leak the uric acid into the blood.
Excess uric acid can form crystals in the synovial fluid between the joints causing inflammation and pain. This condition is called gout and can severely damage the joints if left untreated. The Uric Acid Test can indicate the presence of gout, or risk of formation of gout. However, it is not a definitive test for gout. Confirmatory test for gout is performed by analysis of synovial fluid (joint fluid) for monosodium urate crystals. Chronic Hyperuricemia can cause the formation of tophi, which are hard lumpy deposits of uric acid crystals formed under the skin, in the joints, and at the top of the ears. Tophi cause severe damage to the joints and may compress nerves causing chronic pain and disfigurement. The excess uric acid may also deposit and crystallize in the kidneys causing kidney stones and acute renal failure.
Know more about Uric Acid
Interpreting Kidney Function Test results
Interpretations
These are simple blood tests that can identify some problems with your kidneys.
Abnormal or raised levels than normal may indicate some kidney defect. Abnormal KFT may also indicate that your underlying conditions, like diabetes or high blood pressure, are affecting the kidney.
Note that sometimes, increased levels of the KFT parameters may not necessarily be due to health disorders. For example, increased creatinine levels can occur due to heavy exercise, consumption of cooked meat, or taking protein supplements. Thus, these parameters are also considered while interpreting the tests. Further tests are performed to confirm any health disorders.
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