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.
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.