Blood urea is an important indicator of kidney and liver function. It is examined and evaluated as part of a biochemical analysis. When making a diagnosis, the doctor interprets all the test data in a complex. What is the normal urea content? And what does an increase or decrease in the concentration of this substance indicate? We will answer these questions in the article.
What it is
Urea (urea) is a chemical that is one of the breakdown products of proteins. The process of its formation occurs in the liver. Further, urea enters the bloodstream, is filtered in the renal glomerulus system and excreted from the body. The greatest amount of urea is found in the blood and urine.
Urea synthesis is carried out in several stages:
- Protein compounds enter the body mainly with food. Then they are broken down into amino acids containing nitrogen.
- Amino acids break down into toxic nitrogen compounds. The body tries to neutralize these substances as soon as possible and remove them.
- During the breakdown of amino acids, a toxic nitrogenous compound is formed - ammonia. It is neutralized in the cells of the liver. During the processing of ammonia, urea (urea) is formed.
- From the liver, urea enters the vessels and for some time is in the blood.
- Then it enters the renal glomeruli. There he undergoes filtration, finally cleansed of harmful impurities and leaves with urine.
Urea itself does not bring any benefits to the body. The main objective of this substance is the safe removal of harmful nitrogen compounds.
What does urea in the blood say? By the concentration of this compound, one can judge how well the kidneys and liver function. Also, the level of urea indicates the accumulation of toxic nitrogenous compounds in the body.
What analysis should be passed
How to determine the level of urea in the blood? To do this, you must pass a special analysis on biochemical parameters. This study reflects the state of internal organs and metabolism.
A separate analysis for urea is never carried out. It is impossible to make a diagnosis only by the level of this substance. The urea concentration in a biochemical blood test is always evaluated in conjunction with other data. When the doctor issues a referral for such a study, he marks on the form all types of substances that need to be determined.
In a biochemical analysis, along with the level of urea, the following substances are most often examined:
- Creatinine. This substance is an amino acid that gives energy to muscles. However, in large quantities, creatinine is toxic to the body. The indicator of this compound can indirectly judge the functioning of the kidneys.
- Bilirubin. This is a pigment of bile, which is formed during the breakdown of hemoglobin. Its concentration is not directly related to the level of urea, but also indicates the functioning of liver cells.
- Total protein. This is an important indicator of analysis. After all, urea is formed during the breakdown of white compounds. Usually, if the patient has an increased level of total protein, then the concentration of urea increases.
- Residual nitrogen. This indicator indicates the concentration of toxic nitrogenous compounds in the blood. Their accumulation is extremely dangerous for the body and can lead to severe poisoning. Elevated levels of residual nitrogen are called azotemia.
Very often, patients confuse urea and uric acid. Both of these substances are products of protein metabolism. However, these are completely different compounds. The level of uric acid reflects the state of the musculoskeletal tissue, and the concentration of urea indicates possible impairment of the kidney and liver.
It is important to remember that with a general blood test, urea is not determined. This study has a completely different task. It shows only the number of different types of blood cells. In clinical analysis, the biomaterial is examined under a microscope, and it is impossible to determine the concentration of urea in this way. To find out the indicators of urea and other metabolic products, it is necessary to pass a biochemical test.
Indications for the study
A biochemical analysis is prescribed if the patient has symptoms that indicate abnormalities in the urea index. If the concentration of urea is increased slightly, then this is accompanied by the following manifestations:
- headache and dizziness;
- fatigue
- nausea
- insomnia;
- decreased appetite.
If the level of urea in the blood is significantly higher than normal, then the patient has the following symptoms:
- swelling on the body and face;
- urination disorders;
- high blood pressure.
Such symptoms indicate kidney diseases and intoxication of the body with nitrogen compounds. In severe cases, convulsions and severe vomiting occur, and then the patient falls into a uremic coma.
A decrease in blood urea may not manifest itself. In some cases, patients have the following symptoms:
- a feeling of heaviness on the right side under the ribs;
- losing weight;
- asthenia;
- decreased appetite;
- burp with a taste of bitterness.
Such signs may indicate impaired liver function. However, a decrease in urea concentration is often due to malnutrition or natural physiological causes.
If kidney pathology is suspected, doctors recommend donating blood for urea and creatinine. Both of these substances indirectly indicate the functioning of the excretory organs. If the symptoms indicate a possible liver disease, then the level of urea and bilirubin is determined within the framework of a biochemical study.
Preparation rules
Before blood tests for biochemical parameters, doctors recommend that you adhere to the following rules:
- For 8 - 10 hours before blood donation, refuse to eat.
- The day before the analysis, you should try not to abuse protein foods (meat, fish), as well as sweets.
- On the eve of the study, it is recommended to avoid physical overwork and stress.
- For 1 - 2 hours before taking the sample, you must refrain from smoking.
This analysis is pretty accurate. Random circumstances have little effect on its results. Even if the patient has violated any rule of preparation for the study, this is weakly reflected in the level of urea in the blood. Therefore, the need for re-passing the test is extremely rare.
How do the analysis
Venous blood is taken from a patient for examination. The biomaterial is sent to a diagnostic laboratory. The concentration of urea is determined in the following ways:
- Gasometric. Carbon dioxide is released from the urea by a chemical reaction and its amount is measured. Then, according to a special formula, the initial level of urea is calculated.
- Enzymatic. Urea is broken down by enzymes into simpler substances. Then their quantity is determined and the concentration of urea is calculated by the formula.
- Photometric. Urea is decomposed into individual components using reagents. Then their concentration is measured using a special light device. Urea level is also determined by the formula.
The method for determining the concentration of urea does not affect the results of the analysis. All of the above methods are quite accurate.
Reference values
Normally, the level of urea in the blood in men is from 3.7 to 7.4 mmol / L. For women, a lower concentration of urea is allowed - from 2.3 to 6.6 mmol / l. These reference values apply to a group of patients aged 14 to 60 years.
In older people, urea is usually slightly higher. This is due to an age-related decline in kidney function. For patients older than 60 years, the norm is considered indicators from 2.8 to 7.5 mmol / L.
In childhood, metabolism is quite fast. Therefore, the child’s blood urea level is lower than that of an adult. For infants, values from 1.2 to 5.3 mmol / L are considered normal, and for children 1 to 14 years old, from 1.8 to 6.6 mmol / L.
Non-pathological causes of increased urea
If the content of urea exceeds reference values, then this does not always indicate pathology. After all, doctors always evaluate the results of a biochemical study in a complex. There are times when absolutely healthy people have increased blood urea. What does it mean? Such an analysis result can be triggered by the following non-pathological reasons:
- Excess protein in the diet. The more people eat meat, fish, and other protein-rich foods, the higher the urea concentration.
- Excessive physical exertion. With muscle load, the body takes energy from proteins. As a result, accelerated protein breakdown and enhanced urea synthesis occur. In people involved in power sports, a moderately elevated blood urea is often determined.
- Taking medication. Steroid hormones, androgens, diuretics, and certain types of antibiotics affect protein metabolism and urea formation.
- Emotional overstrain. With frequent stresses, an accelerated breakdown of proteins in the body occurs.
However, dietary and lifestyle features do not significantly affect urea levels. In the above cases, the concentration of urea is only slightly higher than the upper limit of the norm.
Possible diseases
Significantly increased blood urea is most often one of the signs of pathology of the excretory organs. With various diseases in the kidneys, the filtering process of urea worsens. As a result, the level of urea in the blood rises sharply. This is noted in the following diseases:
- acute and chronic renal failure;
- glomerulonephritis;
- pyelonephritis;
- urolithiasis.
In acute and chronic renal failure, creatinine, total protein and residual nitrogen are also higher than normal. The concentration of urea in the analysis of urine is reduced.
The reason for the increase in the content of urea can be a poor blood supply to the kidneys. The nutrition of the excretory organ is impaired by dehydration, shock conditions and severe heart diseases.
However, there are times when the kidneys work fine, but the patient has increased blood urea. What does it mean? In such cases, doctors talk about production azotemia. In this condition, the patient sharply increases the formation of urea in the liver, and the kidneys do not have time to remove a large amount of this substance.
Urea synthesis increases with the following diseases:
- blood diseases (leukemia, leukemia, some forms of anemia);
- infectious pathologies;
- burns;
- bowel obstruction;
- peritonitis;
- shock conditions;
- prostate tumors in men.
Urea levels increase with dehydration. During fluid loss, a decrease in blood volume occurs. This leads to an increase in the relative concentration of urea. At the same time, the synthesis of the substance in the liver and the filtration of urea in the kidneys remain normal. This is noted with diarrhea, severe vomiting, high fever, as well as with large blood loss.
Reduced performance
Low blood urea is quite rare. Such an indicator may be associated with non-pathological reasons:
- Malnutrition. With strict diets and starvation, the body receives few proteins. As a result, the amount of protein metabolism products, including urea, decreases.
- An increase in blood volume. The relative concentration of urea decreases after a dropper or a large amount of fluid.
However, in some cases, liver diseases, metabolic disorders and poisoning lead to lower levels of urea. A low indicator may be a sign of the following pathologies:
- cirrhosis or liver dystrophy;
- protein metabolism disorders;
- intoxication with phosphorus or arsenic.
Urea may also be below normal for hypothyroidism and increased production of growth hormone. Such endocrine pathologies worsen protein metabolism.
Decryption in pregnant women
A low blood urea during pregnancy is considered a normal option. During this period, proteins are intensively formed in the body of a woman, which are necessary for the development and growth of the fetus. If the patient is healthy, then the breakdown products of proteins are completely eliminated from the body.
An increase in blood urea during pregnancy is a rather dangerous sign. This may indicate nephropathy - impaired renal filtration. Also, during the period of gestation, women can experience metabolic disorders and hormonal fluctuations. This also affects the operation of the allocation system. With an increase in urea during pregnancy, it is necessary to consult a specialist and undergo an additional examination.
Decoding in children
If the level of urea is increased in the blood of a child, then this can also be a sign of kidney disease. However, such pathologies in children are quite rare. More often, an increase in urea concentration is associated with the following diseases and conditions of the body:
- food poisoning, accompanied by vomiting and diarrhea;
- infectious pathologies;
- congenital diabetes mellitus;
- burns;
- insufficient protein in food.
If abnormalities in the level of urea are diagnosed in infants, then this may be a sign of serious protein metabolism disorders. Such pathologies are usually congenital and genetic in nature.
A low concentration of urea in children most often indicates hepatitis and other liver diseases accompanied by jaundice.
What to do in case of deviations from the norm
The results of a biochemical blood test must be shown to a doctor. Only a specialist can correctly interpret the analysis data. Additional laboratory and instrumental examinations may be required to provide an accurate diagnosis.
Deviations from the norm of urea indices cannot be considered as a separate pathology. This is just a diagnostic sign of various diseases that require treatment. The concentration of urea is normalized only after eliminating the cause of its increase or decrease.
With severe intoxication of the body with protein breakdown products, the doctor may prescribe the following drugs:
- Lespenephryl.
- "Ornicketil."
- Gepa-Merz.
These drugs not only lower carbamide levels, but also purify the blood. They can be taken only as part of complex therapy and on the recommendation of a doctor.
If drug treatment is ineffective, artificial blood filtration is used using a special apparatus (hemodialysis). Patients with severe renal failure should regularly do this procedure. It effectively purifies the blood from protein breakdown products and prevents intoxication.