Analysis of urine for urea refers to biochemical types of studies. It is not included in the standard survey and are assigned for the diagnosis save the excretory ability of the kidneys.
A substance such as urea in the urine in their diagnostic value is always mapped to the simultaneous study of its content in the blood. The chemical structure of the substance is a salt of carbonic acid (urea).
It is part of the non-protein nitrogenous compounds, together with creatinine, creatine, residual nitrogen, uric acid. While it accounts for up to 75% of the total mass of the group. Therefore, is the most significant component for the study of protein metabolism.
Role in the transformation of proteins
The breakdown of proteins accompanied by the formation of toxic substances – ammonia. With the blood it reaches the liver and is transformed into harmless urea. It should be distinguished from uric acid, which is formed mainly by the decay of nucleic acids.
As unnecessary slag substances urea excreted by the kidneys into the urine by 12 to 36 g per day. Since the process of neutralization of ammonia is constant, this compound is present in the blood and in the urine.
The formation of urea is influenced by:
- protein from food;
- the strengthening of processes of disintegration of the tissues;
- loss of muscle mass.
Urea passes freely through the basal membrane of the glomeruli, is not subject to reabsorption and secretion in kanalzeva apparatus of nephrons
During deceleration of the rate of filtration or flow of primary urine in the tubules, urea is itself returned into the blood. This property allows the level of this substance to determine the rate of renal blood flow.
In the metabolism of urea, in contrast to creatinine, the significant role of the liver. Impaired function of hepatocytes leads to reduced production of urea and a drop in its level in the blood. Finding the causes of changes in the balance of non-protein nitrogen in the direction of increase or decrease allows you to diagnose lose not only the kidneys but also the liver.
What determines the concentration in the urine?
Concentration in urine urea is determined by two factors:
- its concentration in the blood;
- the speed of renal filtration.
Change each of them leads to increased or, conversely, low levels of the substance. For laboratory determination it is important to consider different hourly concentration in urine. She is thrown a portion. Therefore, if we explore the analysis several times a day, the concentration of the substance in one – will be high in the other – a normal or near empty.
This means that to obtain reliable values it is necessary to explore the daily urine (collect, mix and get the average value). Therefore, the rating is determined Molech during the day and reflects the amount of urea.
What is considered the norm?
The level of urea in the blood of a healthy adult is 2.8 to 8.3 mmol/l in the elderly rate of blood is higher (2.9 to 7.5 mmol/l), and the urine is 330-580 mmol per day. Blood women a little less urea, for excretion of the influence of gender is not established.
Levels of emissions of urea excretion in childhood and adolescence are shown in table
|The age of the child||The value in mmol/day.|
|six months or a year||33-67|
|to 15 years||200-300|
As in the laboratory to determine the content of urea?
Analysis of urea is carried out in the Department of biochemical laboratories of medical institutions. Definition of indicator in urine is a rare destination, often exploring the venous blood.
Typically use a standard set of reagents “Areatest”, prepared for comparison, a solution with a content of 1 g of substance per liter. For analysis take diluted with distilled water 25 times and filtered daily urine.
To analyse the required volume of 0.1 ml
The technique is based on the reaction of urea with thiosemicarbazide and ferric salts in an acidic environment. The presence of urea is confirmed by the formation of the compound is red. The intensity of staining depends on the concentration of the solute. Therefore, with the help of photoelectrocolorimetry determined quantitative value.
The laboratory must analyze for 15 minutes, as the colour is unstable. Calculation of urea nitrogen is carried out according to a special formula taking into account the molecular weights of the components.
There is an Express-method. It takes into account the property of urea to decompose under the action of the enzyme urease to ammonia. Released ammonia color strip in blue color. At the height of the zone is judged on the quantity of urea. The calculation is performed with a special calibration schedule.
To Express the technique involves strips of chromatography paper impregnated with the necessary reagents
How to prepare for the exam?
From food the day before urine collection to exclude carrots, beets (change color), meat products. Should not take drugs containing Aspirin, diuretic. Drink the liquid volume change is not required.
To collect the urine will during the day, so you should prepare a clean glass jar (wash with soap and rinse with boiling water). It is necessary to provide a non-working day, peaceful environment.
Women can not analyze when menstruation and during the week after graduation. Blood interferes with the investigation.
At 6 a.m. mandatory hygiene of the external genitalia. The bladder is fully exempt.
Since that time, each time you urination you need to collect urine allocated in the prepared container (jar) for 24 hours. Storage should be ensured in the fridge.
The next day, immediately after a 6 hour emptying the bladder is measured by allocated volume (diuresis) during the day and fit the direction. Of the total banks 20-30 ml is poured into a standard container purchased at the pharmacy. It must be delivered to the laboratory along with a direction for two hours. The delay decomposition begins included in urine substances, the data analysis can be misleading.
When may increase of urea level?
The high content of urea can indicate an increased process of protein breakdown. This condition is not necessarily associated with pathology.
Physiological enhancement of the collapse occurs when:
- the absorption of proteins from food if one eats a lot of meat products;
- of pregnancy, when metabolism (synthesis and breakdown) was significantly reduced.
In the postoperative period, as a result of injuries received in the blood of nitrogenous substances from the disintegrated tissues. Urea is increasing and this figure is regarded as normal.
Pathological causes are:
- exposure to high levels of thyroid hormones thyrotoxicosis;
- febrile condition;
- pernicious anemia;
- overdose or individual sensitivity to the drugs in the group of Aspirin, Quinine, Thyroxine;
- treatment with corticosteroids.
Less growth of urea cause:
- neurological disease with muscle atrophy;
- poisoning by salts of phosphoric acid;
- inflammation of the urinary organs (nephritis, cystitis, pyelonephritis);
- liver damage in hepatitis and cirrhosis;
- prolonged lack of vitamins B1, E and trace element selenium in food and water;
- the hormonal composition in diabetes.
Why the decrease in the level of urea in the urine?
Physiological causes of low may be the condition, delaying the breakdown of proteins due to the increased requirements in building tissues.
- in childhood in connection with increased spending on growth organs;
- during pregnancy in women, if the fetus takes the building materials yourself;
- vegetarians who do not take animal food;
- in the recovery period (recovery) after severe diseases.
The fascination with young men and some women bodybuilding and building muscle accompanied by the administration of specific nutritional compounds, which must include anabolic steroids and vitamins.
Under the influence of cocktails enhanced by education the muscle tissue in the blood is delayed a significant amount of protein, and the secretion of urea is reduced
Pathological causes occur when:
- liver disease (hepatitis, cirrhosis, malignant tumors and metastases from other organs) due to a dysfunction of the cells and a decrease in the synthesis of urea, respectively, its level drops sharply in the blood and in the urine;
- kidney disease in stage renal failure with filtration in the nephrons (glomerulonephritis, amyloidosis, hydronephrosis, tumours), usually in the blood level of urea increases and decreases in the urine;
- the treatment of growth hormone, testosterone, insulin, anabolic drugs;
- congenital deficiency or complete absence of necessary for the synthesis of urea enzymes;
- the septic state.
Why does the diagnosis need to know the ratio of urea in blood and urine?
In diagnosis, the increased urea in the urine is needed to identify the causes of violation of the filtration function of the kidneys. The ratio of the content of this substance in the blood and urine can distinguish between renal and extrarenal conditions. There are different options.
If the blood concentration of urea is higher than normal and the daily release of urine is reduced:
- there is a suspicion on violation of the excretory function of the kidney membrane and connection with diseases of the kidneys;
- possible extrarenal (extra renal) pathology associated with a significant reduction of renal blood flow with stagnation of heart failure, loss of fluids due to massive bleeding, uncontrollable vomiting, diarrhea (cholera).
While increasing the level of urea in blood and urine of the condition is often transient in nature and is associated with increased formation of urea in the blood flow of protein intake.
There is no doubt that renal excretory function is normal, but there may be a serious disease of other organs.
Elevated levels of urea in blood is possible with:
- hemolytic anemia;
- diabetic coma;
- liver failure;
- crush syndrome;
- shock States;
- acute myocardial infarction;
- gastrointestinal bleeding;
- acute poisoning with chloroform, mercury compounds, phenol, oxalic acid.
Acute myocardial infarction – a factor that triggers the increase in numbers of urea
Is it possible to normalize the level of urea?
When the deviation of urea in the urine from the norm is not advised to take initiative for correction. You should consult with your doctor to double-check the analysis to take account of physiological causes.
To detect the pathology of the liver or kidneys, the doctor will schedule additional tests.
Need to check:
- biochemical tests of liver enzymes, protein;
- analysis on the blood levels of other degradation products of proteins (creatinine, residual nitrogen);
- analysis to study the bacterial flora, to identify elements of the inflammation of urinary organs;
- common blood tests.
The ultrasonic method allows to identify pathological changes of the kidneys and liver.
If the person is fond of vegetarianism, heavily involved in sports, the balance changes should correspond to the cause. Improper diet is always fraught with dysfunction of the digestive system. Changes in the liver can be stopped by switching to healthy foods.
Taking anabolic hormones negatively affects not only the condition of the metabolism of urea, but also for synthesis of sex hormones. So under their influence is an “averaging” of sexual characteristics. Men and women often lose their ability to have children.
A study of urea in the urine helps to detect many issues. Often a deviation from the norm serves as a warning about the propensity and probability of development of pathology. The result of the analysis should be treated with due care.