Biochemical analysis of urine
The content of the article:
- Collecting material for analysis
-
The main indicators determined during the biochemical analysis of urine
- Urea
- Uric acid
- Creatinine
- Albumen
- Protein
- Amylase
- Glucose
- Trace elements
Biochemical analysis of urine, or biochemistry of urine - one of the laboratory methods to diagnose diseases of the kidneys, liver, endocrine glands and other organs and systems. It is prescribed for suspected diabetes mellitus, to exclude pathologies of joints and bones, as well as during pregnancy for preventive purposes.
Collecting material for analysis
For biochemical analysis, you need to pass daily urine. How to assemble it correctly? The first morning urination is passed, and all subsequent and first morning urine of the next day is collected in one sterile container - either a special container for collecting daily urine, or a three-liter jar thoroughly washed and sterilized with steam. After collection, the urine is stirred by shaking gently, then approximately 100 ml is poured, which is placed in a separate container and delivered to the laboratory. It is also possible to deliver all the collected daily urine to the laboratory.
Daily urine is collected in a specially designed container Daily urine is collected in a specially designed container
The main indicators determined during the biochemical analysis of urine
In the biochemical analysis of urine, many indicators are determined, but the doctor, as is correct, prescribes a study of only those of them that are required in this case.
Urea
Urea is the end product of the breakdown of proteins and amino acids, therefore, its content in urine makes it possible to assess protein metabolism. The function of urea is to remove excess nitrogen from the body. Urea is formed in the liver, circulates in the body and eventually enters the kidneys, then excreted through the urinary tract.
Normally, up to 20 g of urea nitrogen is removed with urine per day. Nitrogen concentration rates depend on age:
- up to a year - 10–100 mmol / day;
- up to 4 years - 50-200 mmol / day;
- up to 10 years - 130-280 mmol / day;
- up to 15 years - 200-450 mmol / day;
- in children over 15 years old and in adults - 428-714 mmol / day.
Increased consumption of protein with food, hyperfunction of the thyroid gland, increased muscle load, and diabetes mellitus can lead to an increase in the content of urea in urine. Often high urea is detected in people in the postoperative period.
A decrease in the level of urea can be associated with a low protein content in food, liver disease, kidney disease, hormonal disorders. For pregnant women and growing children, low urea levels are normal.
In the course of biochemical analysis, it is often not the amount of urea in daily urine that is assessed, but the purification factor, which in the analysis form can be called "urea clearance" - this is the rate at which the kidneys cleanse the blood from urea.
The rate of the urea purification factor is 40–60 ml / min. If the clearance rate is significantly lower than normal (<10 g / l), and a high concentration of toxic nitrogen is detected in the blood, this indicates renal failure.
Uric acid
Uric acid is the end product of purine metabolism and is normally almost completely excreted from the body in the urine in the form of salts.
With a normal diet, the rate of uric acid in the urine is 1.48-4.43 mmol per day. An increase in the indicator may indicate the development of gout, nephritis, acute renal failure. Some drugs (antibiotics, anesthetics, analgesics) can also lead to an increase in the level of uric acid in the urine, so you should stop taking medications a few days before the study.
Low uric acid levels can be a sign of muscle abnormalities, xanthinuria, lead intoxication, and vitamin B9 deficiency. Medicines containing iodine, as well as quinine and atropine can lower uric acid levels.
Creatinine
Creatinine, one of the byproducts of protein breakdown, allows you to evaluate the filtration rate in the glomeruli of the kidneys. The chain that leads to the formation of creatinine starts in the liver. There, the precursor of creatinine is synthesized - the nitrogen-containing acid creatine. Creatine is involved in energy metabolism in the cells of muscles, heart and nervous system, where it enters with the blood stream. There, in the presence of ATP, creatine attaches the remainder of phosphoric acid and turns into creatinine phosphate, a substance that serves as an energy depot for muscles. During muscle contractions, it breaks down, releasing energy and forming creatinine, which enters the bloodstream and is excreted by the kidneys.
Normal creatinine levels are 5.3-15.9 mmol / day for women and 7.1-17.7 mmol / day for men.
An increase in creatinine may be associated with its increased formation (protein diet, exercise), endocrine disorders (hypothyroidism, acromegaly, gigantism, diabetes mellitus), infectious diseases, massive trauma or surgery, dehydration, and is also characteristic of the acute phase of radiation sickness.
A decrease in creatinine levels can result from diseases of the muscular apparatus (paralysis, dystrophy, polymyositis), kidneys, and hyperfunction of the thyroid gland. Often, increased creatinine is determined in patients with anemia or leukemia.
The creatinine clearance is used to study the rate of renal filtration (GFR), which is examined using the Reberg-Tareev test, a method that determines the concentration of creatinine not only in urine, but also in venous blood. The ratio of these concentrations allows you to know the glomerular filtration rate. The norms for GFR indicators depend on age and sex and are shown in the table.
Age GFR rate, ml / min Children under one year old 65-100 From one to 30 years Men - 88-146
Women - 81-134
30-40 years old Men - 82-140
Women - 75-128
40-50 years Men - 75-133
Women - 69-122
50-60 years old Men - 68-126
Women - 64-116
60-70 years old Men - 61-120
Women - 58-110
Over 70 years old Men -55-113
Women - 52-105
A GFR indicator exceeding the norm can occur in nephrotic syndrome, diabetes mellitus and hypertension. Its decrease, as a rule, indicates renal failure.
Albumen
Albumin are protein compounds formed in the liver. They serve as a reserve of amino acids, participate in the maintenance of normal osmotic pressure in the blood and carry free fatty acids, steroids and vitamins. In the kidneys, albumin is almost completely filtered out and returned to the blood, so only traces of it normally appear in the urine - up to 20 mg / l.
The main causes of increased albumin levels are:
- kidney disease: glomerulonephritis, glomerular nephropathy, pyelonephritis, lupus nephritis, nephrotic syndrome, renal vein thrombosis;
- pathology of the cardiovascular system: arterial hypertension, congestive heart failure;
- disorders of carbohydrate metabolism: diabetes mellitus, congenital fructose intolerance;
- intense physical work;
- hypothermia;
- poisoning with salts of heavy metals;
- sarcoidosis;
- systemic lupus erythematosus;
- pregnancy.
Protein
Normally, protein is practically not excreted in the urine. Filtration takes place in the glomeruli, during which large protein molecules do not pass through the filter and return to the bloodstream. The maximum protein content in urine is normal - up to 150 mg / day (it is possible to increase up to 250 mg / day after heavy physical activity).
Loss of protein in the urine is a sign of a serious disorder in the body. These can be kidney diseases (nephrotic syndrome, glomerulonephritis, diabetic nephropathy, damage to the renal tubules), infections and tumors of the urinary tract, malignant blood diseases, hematuria, congestive heart failure.
Amylase
Amylase is one of the enzymes involved in carbohydrate digestion, the function of which is to break down polysaccharides (starch, glycogen) to glucose. It is formed in the pancreas and salivary glands, from where it is delivered to the oral cavity and duodenum, where the breakdown of carbohydrates occurs. Normally, a small amount of amylase is found in the urine:
- from birth to one year - 5–65 U / l;
- from one to 70 years - 25–125 U / l;
- over 70 years old - 20–160 U / l.
An increased level of amylase is observed in diseases of the pancreas (pancreatitis, cyst, blockage of the duct by a tumor or stone), pathologies of the salivary glands (parotitis, sialodenitis, salivary stone disease), renal failure, intestinal obstruction, diseases of the biliary tract, tumors of the lungs and ovaries, cranial - brain injuries.
Decreased urinary amylase may indicate pancreatic insufficiency, hepatitis, or cystic fibrosis.
Glucose
The content of glucose in urine is one of the markers of diabetes mellitus. Normally, there is no glucose in the urine, appearing only when its concentration in the blood significantly exceeds the norm. If the glucose level exceeds 0.8 mmol / L, they speak of glucosuria. This condition can be physiological - for example, during pregnancy or with an excessive intake of carbohydrates from food. But in most cases, such a result is a reason for additional diagnosis of diabetes mellitus and pancreatic diseases.
During a biochemical analysis of urine, those indicators are examined that are required for a particular patient During a biochemical analysis of urine, those indicators are examined that are required for a particular patient
Trace elements
During the biochemical analysis of urine, the following trace elements are most often examined:
- potassium is an alkali metal involved in the regulation of water-salt metabolism in the body. Affects the heart rate and the functioning of the nervous system, in particular, the conduction of nerve impulses and the state of the brain. Contained in all intracellular fluids. The norm in urine is 30–100 mmol per day. An increase in potassium levels can be associated with trauma, sepsis, blood transfusions, kidney and adrenal gland lesions, as well as with the intake of certain medications - diuretics, steroid anti-inflammatory drugs, diacarb;
- sodium - together with potassium, it is involved in maintaining the water-salt balance, and also affects the production of gastric juice, the activation of digestive enzymes and the work of blood vessels. Normally, 130–260 mmol of sodium is excreted in daily urine. Deviations from the norm can talk about adrenal insufficiency, diabetes mellitus, nephritis, violation of the acid-base balance of urine;
- calcium is an element whose functions are associated with bone metabolism, the work of the nervous system, muscle contractility and blood clotting. The norm of calcium in daily urine is 2.5–7.5 mmol. An increase may indicate disorders of the endocrine system (hyperparathyroidism, Itsenko-Cushing's syndrome, acromegaly, thyrotoxicosis), osteoporosis, impaired renal function, and sometimes malignant tumors;
- Phosphorus is a mineral element that promotes the growth of bone tissue, regulates the metabolism of proteins and fats, and maintains the water-salt balance in the body. The daily rate is 12.9-40 mmol. An increase may indicate kidney damage, urinary stones, or leukemia. Decrease is one of the signs of endocrine diseases and tuberculosis.
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Anna Kozlova Anna Kozlova Medical journalist About the author
Education: Rostov State Medical University, specialty "General Medicine".
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