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Kidney Function Tests

Urea: It is the final product of protein breakdown. It is excreted through the urine. It is toxic when it is high in the blood. If there is a problem in the kidneys that will prevent urea excretion, it rises in the blood. Its increase indicates that the production and destruction of any protein in the body has increased enough to exceed the excretion capacity of the kidney or the presence of a problem such as kidney inflammation (glomerulonephritis), tumor, kidney stone that prevents the kidney from excretion of urea. Urea increase should be intervened immediately.
BUN (Blood Urea Nitrogen): It is the expression of the height of urea in the blood as nitrogen on the urea molecule. Some clinics and clinicians use this test as a different reference in diagnosis and treatment.
Creatinine: It is a protein synthesized in the kidneys, liver, and pancreas. Its task is to provide phosphorus to the muscles during energy synthesis, which is the body's source of life, by keeping phosphorus bound. Once energy is obtained, it is reused to bind new phosphorus molecules. The daily excretion of creatinine in the kidney is about 2 g/day. The rest is kept. Creatinine is an important end product of muscle metabolism and is excreted from the kidneys with urine. If kidney function is impaired, this excretion slows down, and creatinine rises in the blood. There is no clinical significance if the creatinine level is lower than normal. If creatinine is high in the blood, it is necessary to re-conduct the test with creatinine in the urine for 24 hours to understand kidney function. This test is called creatinine clearance.
Uric Acid: Uric acid is the product of the destruction of ATP, the body's energy-providing molecule, and DNA fragments in cells that have lost their lives. When these breakdowns increase, uric acid rises in the blood. If it cannot be excreted by the kidney for any reason, it crystallizes by accumulating in the joint fluids and surrounding tissues since it has acid properties. It causes gout. Consuming foods containing uric acid and young animal meat in particular increases the level of uric acid in the blood. 
Urine Analysis: Urine can be defined as a filtrate produced by the kidneys, which acts as the sieve system of the blood. While the metabolic residues (toxins) in the body are thrown out with the help of water, some molecules, minerals, and vitamins that are not wanted to be removed are separated and kept. Their excretion in the urine is directly related to their blood values. When these substances rise above a specific value in the blood, the kidney's filtering capacity becomes insufficient, and the filtering tubes (glomeruli) are blocked. Seeing these obstruction-causing substances in the urine with a microscope indicates that the kidney tubules have begun to be damaged. Although a substance that rises above a specific rate in the blood is excreted from the kidney, there is a speed and capacity at which each substance can be excreted. This is called the threshold value of the kidney for this substance. For instance, this is 180 mg/dl for glucose. In other words, when glucose rises above 180 mg/dl in the blood, abnormal glucose begins to appear, and abnormal glucose values are observed in the urine. It is also acceptable for urobilinogen, which is the bile form of bilirubin in the urine, and bilirubin and albumin (protein), which are its different forms in the blood. During prolonged hunger or pregnancy, when the baby uses sugar, the body tries to obtain its energy from fats. And consequently, ketone bodies (acetone in the urine) are formed in the blood, which is acidic and toxic. It should not be too high in the blood. The appearance of it in the urine indicates that this level has increased.
If there is a bacterial infection in the urinary tract or bladder, it is detected by nitrite produced from bacteria. The color and density of the urine may alter due to the substances excreted in the urine and the presence of more or less water in the body. For instance, if there is the protein in the urine, the urine becomes a cloudy and dense liquid. If there is bilirubin in the urine, the color of urine becomes dark yellow. Also, the color of urine becomes dark yellow when taking vitamins A and B. The presence of sugar, albumin, and other metabolites in the urine thickens the urine.
The shaped elements (cells and crystals) in the urine settle to the bottom when centrifuged (swirled rapidly at 5000 rpm) in the tube. This precipitation is examined under a microscope. Based on the structures of the cells, it can be reported whether there is a blockage in the kidney tubulins, inflammation and bleeding in the bladder and urinary tract, and damage in the urinary tract and bladder. Certain shaped elements in the urine, which should be in an above-normal number of cells or not, indicate certain diseases.