LFT and KFT (Liver Function Test & Kidney Function Test)

The Bilirubin Total measures the amount of bilirubin present in the blood of a person. Bilirubin is an orange-yellow waste pigment produced by the normal breakdown of heme. The heme is a component of hemoglobin and is found in red blood cells. The liver processes the bilirubin and eliminates it from the body. 

The life span of red blood cells is about 120 days. The heme which is released from the hemoglobin is converted into bilirubin which is called unconjugated bilirubin. It is then carried to the liver by proteins, where it gets attached to sugars and becomes conjugated bilirubin. This conjugated bilirubin enters the bile from the liver and passes to the small intestine. Here, it gets broken down by the bacteria and further gets eliminated in the stool. These breakdown products of bilirubin are responsible for giving the characteristic brown color to the stool.

A healthy adult body produces approximately 250 - 350 mg of bilirubin daily. About 85% of bilirubin comes from damaged or degraded RBCs while the remaining amount comes from the bone marrow or liver.

Small amount of unconjugated bilirubin is released in the blood normally, but there is no virtual presence of conjugated bilirubin in the blood. 

Both the forms of bilirubin can be measured or evaluated by the laboratory tests, and total bilirubin (sum of conjugated or unconjugated bilirubin) may be reported. In case there is an increase in levels of bilirubin, there will be yellowing of the skin and white of the eyes, giving the appearance of jaundice.  

The Protein Total, Serum Test measures the total amount of the various types of proteins in the serum. Proteins are known as building blocks of all cells and tissues. They are very important for the growth and development of the body. The proteins are responsible for forming the structural part of most of the organs and help in making up of enzymes and hormones which regulate the functions of the body.

In the blood, two classes of proteins are found which include albumin and globulin. Around 60% of the total protein is formed of albumin which is produced by the liver. Albumin works as a carrier protein for various small ions and molecules. It also acts as a source of amino acids for tissue metabolism and as the principal component which is involved in the maintenance of osmotic pressure.

The rest of the proteins present in the plasma are globulins which include enzymes, antibodies, carrier proteins, hormones, and various other types of proteins. In the blood, the protein total serum levels are relatively stable, which means that there is a fine balance in the loss and production of the protein molecules.

If this delicate balance is disturbed due to any illness or disease then this test is done to analyze the reason for it.

The Potassium Test measures the concentration of potassium in the blood.

Potassium is one of the essential body electrolytes along with sodium, chloride, bicarbonate, etc. As an electrolyte, potassium helps to regulate the amount of fluids present in the body and to maintain a correct pH balance. It performs a vital role in cellular metabolism and transport of nutrients and waste products in and out of cells. It is also essential in the transmission of nerve impulses to muscles and muscle activity.

Sufficient amount of potassium required by the body is absorbed from dietary sources, and the remaining unabsorbed potassium is excreted by the kidneys. Body potassium is maintained within a small normal range principally by the hormone aldosterone. Aldosterone acts on the nephrons in the kidneys and activates a sodium-potassium pump which helps the body to reabsorb sodium and excrete potassium. This helps to maintain the potassium concentration in the blood within its normal range. Deviation of potassium concentration from its normal range gives rise to Hyperkalemia (high potassium level in blood), or Hypokalemia (low potassium level in blood). Both these conditions may produce a number of symptoms, and may even be fatal if not controlled.

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.

Chloride is an essential mineral which acts as an electrolyte along with potassium, sodium, bicarbonate, etc. It helps to maintain the normal fluid and electrolyte balance of the body. It also acts as a buffer to help maintain the pH balance of the body. It also plays essential roles in metabolism. Chloride is used by the stomach to produce hydrochloric acid (HCl) for digestion. Chloride is present in all body fluids and is found in highest concentration in the blood and extracellular fluid (fluid present outside the cells).

Most of the chloride intake is through dietary salt (sodium chloride or NaCl), and a small portion through other food items. The body absorbs the required amount and the kidneys excrete the remaining through urine. The concentration of chloride in blood is maintained within a very narrow range by the body and usually increases or decreases in direct correlation with sodium levels.

The Sodium test measures the concentration of sodium in the blood.

Sodium is an essential body electrolyte which, along with potassium, chloride, bicarbonate, etc., helps to maintain the normal fluid and pH balance in the body. It is also vital for cellular metabolism, and in the activity of nerves and muscles and transmission of impulses between them. Sodium is present in all body fluids and is found in highest concentration in the blood and extracellular fluid.

Sodium is supplied to the body principally through dietary salts (sodium chloride or NaCl), and a small portion of sodium is absorbed through other food items. The required portion is absorbed by the body and the remaining is excreted by the kidneys through urine. The body maintains a very narrow range of sodium concentration by three mechanisms:

·         Secretion of hormones natriuretic peptides and aldosterone to control sodium elimination through urine

·         Secretion of antidiuretic hormone (ADH), also called Vasopressin, to control the volume of water eliminated through urine

·         Induction of thirst

Any disruption in the abovementioned mechanisms gives rise to an imbalance in the concentration of sodium in the blood to produce Hyponatremia (low blood sodium concentration), or Hypernatremia (high blood sodium concentration). Both these conditions produce a number of symptoms and may even lead to death.

Urea is a byproduct of protein metabolism. Proteins consumed in the diet are digested and converted into amino acids, which are utilized by the body. This metabolic process creates toxic byproduct ammonia. This byproduct is rapidly converted by the liver to form urea, which is less toxic and is transported relatively safely in blood. Following this, urea is transported by the blood to the kidneys. The kidneys then filter it out of the blood and excrete it out of the body in a solution called urine. This process continues and the body keeps producing and excreting urea, hence maintaining a low and steady level of urea in the blood.

The BUN test measures the amount of urea present in the urea. The levels of BUN test in the blood are affected due to impairment of kidney function, or due to large scale liver conditions. Primarily, BUN Test results are used to evaluate kidney functioning. Results are often interpreted together with results of Creatinine Tests that measure the levels of another metabolic waste (creatinine), which is also excreted in the urine.

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 the 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.