Urea is one of the products formed after the breakdown of proteins in the body. It is constantly formed in the liver and excreted by the kidneys. Urea in the blood is an important indicator of the functioning of the kidneys, namely their ability to remove metabolic products from the body with urine.
Its level is determined during a biochemical blood test. Any deviations of this indicator from the norm indicate pathology.
Urea and uric acid, which is formed during the breakdown of nucleic acids, should not be confused.
How is it formed
The breakdown of protein, which is constantly synthesized in the body, is a complex process with the release of various substances. Some proteins break down, some are converted to another form. When decomposed, a metabolic by-product is released - ammonia. This is a very toxic substance. It poses a particular danger to the brain.
Therefore, ammonia must be neutralized and removed from the body as quickly as possible. It is detoxified by the liver and converted into urea for subsequent excretion. Urea has a very high penetrating ability and easily enters the bloodstream. When blood is filtered by the kidneys, large amounts of urea enter the primary urine, but up to 70% is reabsorbed in the renal tubules. In total, approximately 90% of urea is excreted through the kidneys, and only 10% through the skin and gastrointestinal tract.
What is urea
Urea is a product that is formed in the liver as a result of the synthesis of ammonia and carbon dioxide. The resulting compound is delivered by blood to the kidneys, where the filtering organ separates it from the general bloodstream and sends it into the urine.
Urea is a product unnecessary by the body, which must be completely eliminated, since its accumulation gives an osmotic effect, which can cause swelling of the internal organs in which it accumulates:
- liver;
- kidney;
- thyroid gland;
- spleen;
- pancreas.
Normally, the final product - urea - should be excreted from the body, but if there are any abnormalities in the functioning of the system, it is detected in the blood.
Norm
This indicator is measured in mmol per liter of blood. The norm depends on age and has the following values:
- from 1.8 to 6.4 mmol/liter – for children under 14 years of age;
- from 2.5 to 6.4 mmol/liter – for adults up to 60 years of age;
- from 2.9 to 7.5 mmol/liter – for people over 60 years of age.
Children have lower blood levels than adults. The exception is newborns who develop physiological azotemia due to lack of fluid in the first few days of life. As a rule, a week after birth, its concentration returns to normal.
Urea molecule
Women's urea levels are usually slightly lower than men's. In people whose age has exceeded 60 years, its content increases slightly due to a decrease in the ability of the kidneys to concentrate urine.
If its level in the blood is within normal limits, this indicates that the rate of conversion of ammonia into urea by the liver corresponds to the rate of excretion of metabolic products by the kidneys.
Standards may vary from laboratory to laboratory, depending on the reagents used.
Blood urea level test
Short description:
Urea is one of the end products of protein metabolism, containing nitrogen. It is produced in the liver, transported by the blood to the kidneys, where it is filtered through the glomerulus and then excreted. The blood urea test result is an indicator of glomerular production and urine excretion. The accumulation of urea and other nitrogen-containing compounds in the blood due to renal failure leads to uremia. Synonyms (rus): Carbonic acid diamide, urea, urea in the blood. Synonyms (eng): Urea nitrogen, Urea, Blood Urea Nitrogen (BUN), Urea, Plasma Urea.
Method: UV kinetic using urease and glutamate dehydrogenase.
Units of measurement: mmol/l (millimoles per liter).
Preparing for the study:
• Do not eat for 12 hours before the test. • Avoid physical and emotional stress and do not smoke 30 minutes before donating blood.
Type of biomaterial: Venous blood. Type of tube: vacuum tube with clotting activator and separating gel (red cap with yellow ring).
Service price: 60 rub.
Completion time: one business day.
Reference values:
Age, gender Reference values: < 4 years 1.8 - 6 mmol/l 4 - 14 years 2.5 - 6 mmol/l 14-20 years 2.9 - 7.5 mmol/l 20 - 50 years male 3, 2 - 7.3 mmol/l female 2.6 - 6.7 mmol/l > 50 years old male 3.5 - 8.2 mmol/l female 3.0 - 7.2 mmol/l
Reasons for increased urea levels in the blood: • decreased kidney function caused by congestive heart failure, loss of salts and fluids, shock combined with excessive protein catabolism (gastrointestinal bleeding, acute myocardial infarction, stress, burns), • chronic kidney disease (pyelonephritis , glomerulonephritis, amyloidosis, renal tuberculosis, etc.), • obstruction of the urinary tract (bladder tumor, prostate adenoma, urolithiasis, etc.), • bleeding from the upper gastrointestinal tract (peptic ulcer of the stomach, duodenum, cancer of the stomach, duodenum etc.), • diabetes mellitus with ketoacidosis, • increased protein catabolism in cancer, • taking corticosteroids, nephrotoxic drugs, tetracyclines, excess thyroxine, • use of anabolic steroids, • high protein diet (meat, fish, eggs, cheese, cottage cheese).
Reasons for a decrease in the level of urea in the blood: • liver failure, some liver diseases: hepatitis, cirrhosis, acute hepatodystrophy, liver tumors, hepatic coma, poisoning with hepatotoxic poisons, drug overdose (this disrupts the synthesis of urea), • acromegaly (a hormonal disease characterized by increased production of growth hormone), • fasting, low-protein diet, • impaired intestinal absorption (malabsorption), for example, with celiac disease, • nephrotic syndrome (increased excretion of protein in the urine, hyperlipidemia, decreased protein levels in the blood), • increased production of antidiuretic hormone ( ADH) and, as a consequence, pathological hypervolemia, • pregnancy (increased protein synthesis and increased renal filtration cause a decrease in the amount of urea in pregnant women).
Code A09.05.017
Reasons for the downgrade
A decrease in this indicator is observed infrequently. Since urea is formed in the liver, its reduced level is most often associated with a decrease in the functions of this organ. In addition, the decrease may be due to gastrointestinal diseases, in particular impaired absorption of substances that form proteins.
The causes of low levels can be both physiological and pathological. The first includes:
- pregnancy, during which the water content in the blood increases due to physiological reasons (protein is intensively consumed due to fetal growth); in addition, during the gestation period, a drop in level may be associated with increased fluid consumption; in later stages - with increased protein utilization;
- hyperhydration (excess water) with parenteral (bypassing the gastrointestinal tract) administration of fluid;
- hemodialysis (blood purification without the participation of the kidneys);
- diet poor in protein products, diets, vegetarianism.
One of the causes of low urea is cirrhosis of the liver.
Pathological causes include the following diseases:
- chronic pancreatitis;
- malabsorption in the intestine;
- enzyme deficiency (congenital) that is involved in the formation of urea;
- nephrotic syndrome;
- helminthic infestations;
- complications after intestinal surgery.
Very low urea is observed in severe and life-threatening diseases, namely:
- malignant tumors;
- cirrhosis of the liver;
- acute liver necrosis;
- liver failure caused by poisoning with various hepatotropic toxins, including arsenic, phosphorus;
- hepatic coma;
- viral hepatitis;
- alcoholic hepatitis.
Symptoms indicating increased urea
Based on his feelings, the patient himself can often tell that the level of urea in the blood may be elevated. This is primarily indicated by pain in the lower back in both men and women. It indicates kidney disease.
Separately distinguished:
- swelling;
- increased amount of urine produced;
- scanty urine production;
- the presence of protein in the urine.
However, indications for donating blood for urea may be:
- ischemic diseases;
- hepatitis;
- cirrhosis;
- decreased absorption of foods;
- connective tissue diseases.
The level of urea indicates several possible pathologies at once, so this analysis is often used to monitor the patient’s condition.
Symptoms
With a reduced level of urea, symptoms are not always present or may not be expressed. The following signs may indicate diseases of the gastrointestinal tract and liver, which caused a drop in this indicator:
- loss of appetite;
- constant bloating;
- bitter belching;
- discomfort in the right hypochondrium;
- weight loss;
- muscle weakness;
- swelling;
- feeling of constant fatigue.
With such symptoms, it makes sense to consult a doctor for examination, including a biochemical blood test.
Why might urea be elevated?
To determine the level of urea in the blood, a laboratory method called a biochemical blood test is used. It involves taking material from a vein. For each age category of patients there is its own norm for urea content in the blood:
- in newborns from 1.7 to 5;
- in children of the first year of life from 1.4 to 5.4;
- from one to 15 years old can have 1.8-6.7;
- women over 18 years old - from 2 to 6.7;
- men over 18 years old - from 2.8 to 8.
Several factors influence the urea content. One of which is the level of amino acids in the body, since ammonia is formed from them during metabolism, which becomes one of the components of urea. On the other hand, with a sufficient amount of amino acids, the diseased liver will not be able to synthesize urea, which will be the reason for the detection of its negligible amount. The third important factor is the performance of the kidneys, which must, by filtering the blood, extract urea from it and send it out of the body with urine.
If we exclude all possible pathologies, then we can say that the following factors not related to the disease can increase the level of urea in the blood:
- on the eve of the collection of material, severe emotional stress was experienced;
- the patient had to buy and take a drug from the list: Tetracycline, Euthyrox, Neomycin, Lasix, any drug from the group of corticosteroids or sulfonamides, anabolic steroids, steroids, salicylates;
- the patient fasted for a long time or, on the contrary, ate a lot of protein foods;
- the patient on the eve of the delivery of the material or daily subjected the body to heavy physical activity.
When a doctor tries to determine the quality of kidney function, the presence of urea in the blood may indicate:
- blockage of the urinary ducts;
- chronic. renal failure;
- glomerulonephritis;
- pyelonephritis;
- dehydration, which could be preceded by myocardial infarction, shock or heart failure.
Separately, we should highlight the reasons why urea is formed in the human body in huge quantities:
- prostate neoplasms;
- burn disease;
- severe intestinal infections;
- hematological diseases;
- state of shock.
To accurately determine the patient’s condition, it is necessary to conduct several laboratory tests in a row to see the picture in dynamics; in addition, it is necessary to measure the amount of urea in the urine in order to be able to compare this indicator with blood data.
Symptoms of Low Urea Levels
If urea is low in the blood, then this condition cannot always be detected independently. People most often attribute the symptoms that arise to other causes.
However, there are signs that should alert a person and force him to see a specialist:
- Decreased performance.
- Lack of appetite.
- Flatulence.
- Pain in the right side under the ribs.
- Losing weight.
- Muscular weakness.
- Swelling.
Finding the problem is not difficult. To determine the quantitative content of urea, it is enough to donate blood for a biochemical analysis.
How to take a urea test correctly
You need to prepare for the analysis so as not to receive distorted data. First of all, you need to remember that blood is donated strictly on an empty stomach. In addition, since urea production is affected by the breakdown of muscle fibers, it is important to avoid physical activity on the eve of the test. If you can’t get to the laboratory without excessive physical activity, you need to arrive at the door of the office no later than half an hour before the appointed time in order to have time to calm down and put your nervous system in order.
If the patient is taking any medications, it is better to postpone the morning dose until the blood has already been donated. Immediately before the donation, you should not do massages, biopsies, or x-rays, especially those using contrast.
