How is urine density measured? Why the relative density of urine is increased and treatment. Why is it measured?
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Clinical examination of urine is a universal way to detect pathology at an early stage. It is prescribed as part of any diagnosis or preventive examination. In addition to the presence of blood, bacteria, odor, color and other indicators, the analysis form reflects the relative density of urine. This article talks about what this means and what changes in this value indicate.
Definition, norms
The specific gravity or relative density of urine depends on its saturation with substances (proteins, glucose, bacteria, inorganic sediment); the abbreviation SG is displayed in the results form. Density reflects the physical properties of urine, the ability of the kidneys to filter it, concentrate it and maintain homeostasis (the balance of fluids in the body).
- The normal specific gravity of urine for adults is 1017 - 1025 g/l. This indicator is not static, changing depending on the time of day, the quality and quantity of food consumed, fluids, medications, physical activity and air temperature.
- In women during pregnancy, urine density standards are wider due to the physiologically increased load on the filtration organs and hormonal changes. The norms for specific gravity in the urine of a pregnant woman range from 1001 to 1035 g/l.
- The normal density of a child’s urine differs from that of an adult. Fluctuations in reference values are caused by the instability of the processes regulating fluid metabolism in a continuously growing organism. In infants under one year of age, the normal specific gravity of urine is considered to be from 1005 to 1018 g/l. In children from one to 4 years of age, the boundaries of adequate values narrow - 1010 - 1015 g/l. After 5 years, the specific gravity of urine in children gradually increases, leveling off with the standards for adults by 14–17 years.
A one-time fluctuation in the specific gravity of a urine test is not a cause for concern. To talk about a filtration disorder, it is necessary to observe a persistent change in urine density over 3 months. High or low specific gravity of urine may occasionally appear in a healthy person under the influence of external factors.
Physiology, importance of urine formation
Excreted urine is the end product of metabolism, breakdown, and filtration of substances in the body. Before being released during a visit to the toilet, urine goes through several phases of formation.
From the tubular system of the kidneys, primary urine, similar in composition to plasma without proteins, is filtered into their lumen from the blood. The saturation of this liquid with nutrients is much higher than that of the final product, its amount reaches 150 - 180 l/day. Next, reabsorption (reabsorption) of amino acids, sugars, vitamins and salts from the lumen of the renal tubules into the secondary network of capillaries occurs. As a result of this reaction, a final urine volume of 1.5 - 2 l/day is formed.
Next comes secretion, during which large molecules of substances are removed from adjacent tissues through the vascular system into the liquid medium. As a result, the blood is cleared of particles of drugs, dyes, and decayed microorganisms. Fully filtered urine from healthy people contains only harmful impurities that need to be removed. The content of such substances is about 5% of the total mass of the liquid, the rest is water.
The importance of urine formation and concentration:
- Removal: end products of protein breakdown (creatine, creatinine, urea, uric acid), foreign substances (drug particles, food and non-food dyes), excess organic compounds received from food or formed as a result of metabolic reactions (amino acids, sugars).
- Cleansing and maintaining the normal acid-base reaction of the blood.
- Stabilization of ionic composition, osmotic pressure (balance of salt concentration in fluid and tissue environments of the body), fluid levels.
- Maintaining stable blood pressure.
Analysis of the composition and properties of urine gives an idea of the success of these processes and the presence of pathology.
Change in specific gravity
Physiological fluctuations in urine density in an adult within the range of 1010 - 1027 g/l are acceptable. A natural increase in specific gravity occurs in the morning due to sedimentation and secondary reabsorption of urine at night, slowing down the processes in which liquid is excreted in another way - breathing, sweating. If the density of urine is much higher or lower than normal, we are talking about pathology of the excretory, endocrine, nervous or cardiovascular systems.
Hypersthenuria
This term refers to increased density of urine (more than: 1030 g/l in adults, 1040 g/l during pregnancy, 1025 g/l in children). In diseases with this symptom, the discharge acquires a dark brown, brown color, an unpleasant odor, a tendency to swelling, abdominal pain, general lethargy and apathy.
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Pathological reasons for changes in urine density above normal:
- Acute inflammation of the genitourinary system (cystitis, glomerulonephritis, sexually transmitted diseases). With them, the production of leukocytes, protein, and purulent sediment increases.
- Fluid retention in the body, increasing edema in chronic cardiovascular and renal failure. Accompanied by oliguria - a sharp decrease in the volume of secretions (up to 0.5 liters per day).
- Uncontrolled diabetes mellitus, in which there are elevated levels of glucose in the blood and other body fluids.
- Weakness, abdominal pain, and a strong unpleasant smell of urine mean poisoning with heavy metal salts, which are partially excreted in urine.
- Taking certain medications - antibiotics, X-ray contrast agents for intravenous use. In this case, the specific gravity of urine is increased due to the content of large molecules of the drug substance in it.
- Severe dehydration in gastrointestinal diseases, accompanied by diarrhea and vomiting. Reducing the volume of fluids in the body increases the concentration of secretions. This phenomenon can be observed with toxicosis in pregnant women.
- Injuries to the abdominal organs and intestinal obstruction lead to disruption of the normal functioning of the urinary organs.
- In young children with thermoregulation disorders, increased physical activity (during the hot season), excessive sweating is observed, which gives an increased concentration of urine.
A diet with a lot of dark meat, fatty and spicy foods, and insufficient water intake can lead to the fact that the normal level of urine density will be exceeded. Normalizing the diet and water-salt balance allows you to avoid resorting to serious therapy.
Hyposthenuria
This term is used when talking about a decrease in the specific gravity of urine (less than 1010 g/l in adults, 1000 g/l during pregnancy, 1003 g/l in children). In a healthy person, the specific gravity of urine is reduced when drinking a large volume of liquid (more than 3 liters per day), for example, in hot weather.
- Diabetes insipidus (diabetes) can be a serious cause of low urine density. It is associated with improper functioning of the parts of the brain responsible for regulating fluid metabolism. In neurogenic diabetes, the production of antidiuretic hormone (ADH), which maintains a constant water-salt balance and vascular pressure in the body, is reduced. Diabetes insipidus is an indicator of tumor, metastatic processes in the central nervous system, and traumatic brain injury. There is a genetically determined form. The condition is accompanied by constantly increased thirst (polydipsia) and urination (polyuria, up to 10-15 liters per day).
- Kidney damage that affects the ability to filter substances dissolved in the blood plasma also leads to low urine density. This group includes: cysts, kidney abscesses, nephritis, nephrosclerosis (connective tissue degeneration).
- In pregnant women, a decrease in the specific gravity of urine is acceptable. Low urine density is caused by active production of sex hormones, compression of the excretory apparatus by the growing uterus, and changes in the concentration of minerals and salts.
- When the relative density of urine decreases, the reasons may be hidden in the abuse of alcoholic beverages. This is often observed in men with an addiction to beer, which itself is a diuretic product.
- Resolution of fluid stagnation, edema, long-term infusion therapy (droppers), and taking diuretic medications are accompanied by an increase in the secretion of low-density urine.
Important! Under no circumstances should you self-prescribe diuretics without medical supervision. The use of synthetic and herbal diuretics for weight loss can lead to disastrous consequences. Together with water, vital elements are removed - potassium, magnesium, phosphorus, calcium. The consequences of uncontrolled treatment can be muscle cramps, interruptions in heart function, brittle bones, and destruction of tooth enamel.
The concentration of substances in urine directly depends on the quality of nutrition. Nutritional errors can provoke the development of hyposthenuria. This condition can be easily corrected by changing your diet.
Preparation, analysis
The natural color of urine is light to dark yellow. Excessively dark or transparent discharge indirectly indicates an increase or decrease in urine density. To find out this, a clinical analysis and determination of the relative density of urine are prescribed.
For a correct result, proper preparation for the test is necessary. It is necessary to collect the average portion of morning secretions - they contain the maximum concentration of salts and urea. A clean, dry container with the sample is delivered to the laboratory within 2 hours from the moment of urination. Further sedimentation of urine leads to sedimentation, oxidation of the liquid and a false result.
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Determination of specific gravity in urine analysis is carried out using a urometer. The measuring device looks like a thin thermometer with an oval hollow balloon at the end and a scale with divisions. It is placed in a flask with urine, the position is leveled, and the lower level is marked on the scale. The urometer is configured to operate at an ambient temperature of 12 - 18°C. When the temperature changes, adjustments are made to the obtained data - for every 3°C above/below the norm, 0001 g/l is subtracted/added.
Zimnitsky test
In order to analyze the concentration ability of the excretory apparatus, a Zimnitsky test is prescribed. All daily urine is collected in 8 clean jars and delivered for analysis along with information about the amount of liquid consumed during this period. The patient needs to empty his bladder into the toilet at 6 am, then he urinates exclusively in containers, consistently replacing them every 3 hours until 6 am the next day.
The diet during urine collection for the Zimnitsky test is standard; it is recommended to drink no more than 1.5 liters of fluid per day. Thanks to this analysis, it is possible to track daily fluctuations in the amount and specific gravity of the liquid. The average relative density of urine and the ratio of daytime and nighttime diuresis are calculated. Normally, 2/3 of the total daily urine is excreted during the day, the total amount of fluid excreted is 4/5 of the amount drunk.
As an additional study of the dynamics of the concentration of secretions, specific samples with water loading or limitation are used. The conditions for conducting the latter are often difficult for the subject (soups, sauces, tea and other drinks are excluded from the daily menu; only a few sips of liquid are allowed). It is important to understand that such a study allows us to detect a violation of the filtration of blood plasma of central origin (associated with the pituitary gland, as in diabetes insipidus). 2-3 days before the test, drug therapy that increases diuresis and drugs that can affect the production of hormones involved in the process of urine formation are discontinued.
During dynamic observation, urine testing is repeated at different times of the year. This is due to changes in air temperature, physical activity, and the amount of water consumed. The dependence of the saturation of secretions with substances on these parameters is determined.
Special tests and a general urine test are complemented by checking blood counts. These fluids in the body are continuously connected. If the density of urine is increased/decreased, there will be a high/low concentration of clinical and biochemical indicators in the blood - blood cells, bacteria, inorganic sediment.
Important! When collecting urine from a child, it is necessary to create conditions for him to urinate directly into the container. It is forbidden to pour urine from a pot or squeeze it out of a diaper or diaper - this guarantees deliberately incorrect indicator values.
Treatment, prevention
A change in the specific gravity of urine does not require any special treatment measures, being only a signal of a disorder. Treatment tactics depend on the underlying cause of the disease. You should start by consulting a urologist, nephrologist and endocrinologist.
- Treatment of renal syndromes is aimed at restoring the function of formation and excretion of urine. They use sorbents, diuretics, and for infections - antimicrobial drugs. In case of edema characteristic of chronic renal and heart failure, means of dilating peripheral vessels are used to relieve the main circulation. In case of significant deterioration of the condition, extracorporeal blood purification is used using special devices - dialysis, ultrafiltration, hemosorption.
- To reduce the effects of dehydration, rehydration therapy is prescribed with intravenous infusion of large volumes of solutions of salts and colloids. To prevent the consequences of toxicosis, pregnant women are recommended to take vitamin and mineral complexes.
- The neurogenic, endocrine nature of urinary disorders often requires lifelong replacement therapy with synthetic hormones. Tumors are subject to surgical treatment.
- To prevent urinary pathologies, a specialist will recommend a gentle (depending on concomitant diseases) diet and adherence to a water regime. Moderate physical activity, giving up bad habits and timely examination will help reduce risks and improve the general condition of the body.
The reasons why the specific gravity of urine changes can be natural or pathological. If any alarming changes are detected in the body, preventive diagnostics should be carried out. Treating an advanced disease is much more difficult than preventing it.
A person has to deal with various medical services throughout his life. This could be a consultation with a medical specialist, examination of any biomaterials, examination of internal organs, or taking various medications. Absolutely all people take a general urine test; it is prescribed to all people - from infants to pensioners. This is the most common and at the same time informative method of examining urine.
General what kind of research is this?
The analysis data is an indicator of kidney function, so at the slightest suspicion of kidney dysfunction, doctors prescribe this study. In addition, the results of the analysis may indicate other pathological processes in the body. This method can detect improper functioning of organs by determining the general properties of urine and microscopy of urinary sediment. The main parameters by which the doctor draws conclusions about the patient’s condition are the following:
- urine color;
- its transparency;
- urine density;
- presence of protein;
- acidity;
- glucose indicators;
- what is the patient's hemoglobin level?
- bilirubin;
- urobilinogen;
- nitrites;
- Availability ;
- epithelium;
- red blood cell count;
- leukocytes;
- what bacteria are in the urine;
- cylinders.
This study is prescribed quite often for patients with kidney pathologies to monitor the dynamics of changes in the functioning of the excretory system and the effectiveness of the medications used. A healthy person should ideally undergo this test 1-2 times a year for timely detection of pathologies.
What are the rules for collecting analysis?
The research must be carried out with utmost precision. It must be ensured from the beginning of urine collection to the final results. Before collecting urine, it is necessary to carry out hygiene of the relevant organs. Please note that various food jars or containers are not suitable for analysis. To collect biomaterial, a special container is required, used only for these purposes. You can buy it at any pharmacy.
In the evening before the test, you need to limit the consumption of foods that can color the urine: beets, carrots and others. In addition, you need to monitor the use of various medications the day before, as they can distort test results. During menstruation, the results may also be false, so you need to wait until the end of this period.
You should not drink alcohol the evening before the test. The content of trace elements in urine can change significantly.
What can be revealed using this analysis?
A general urine test is prescribed to determine the condition of the body if certain pathologies are suspected. This analysis is prescribed when diseases of the urinary system occur, to determine the dynamics of the disease and control it. The analysis helps to prevent possible complications in time, and also shows the effectiveness of the treatment. This study is also often used in examinations of people undergoing medical examinations.
Determination of urine density
The density of urine is the relative ratio of the densities of two materials, one of which is considered as a standard. In this case, the sample is distilled water. The density of urine is usually variable. The reason is that the density changes over the course of a day, this is explained by the uneven excretion of metabolic products dissolved in the urine.
When filtering the blood, the kidneys produce primary urine, most of which is reabsorbed and returned to the bloodstream. Based on the process described, the kidneys make a concentrate of secondary urine. The process described above is called concentration. If the latter is disrupted, this will lead to a decrease in the relative density of urine. Diabetes insipidus, some variants of chronic nephritis and other diseases can impair the concentration function.
If protein, sugar, leukocytes, red blood cells, and the like appear in the urine, this helps to increase the density of urine. The relative density of urine, or more precisely, its average value depends on the age of the person. The concentration function of the kidneys also depends on age. Generally speaking, these two concepts are closely related.
Physiology of urine density
The density of urine, or more precisely, the process of its formation, consists of three stages. These are filtration, reabsorption and tubular secretion.
The first stage - filtration - occurs in the Malpighian corpuscle of the nephron. It is possible due to the high hydrostatic pressure in the glomerular capillaries, which is created due to the fact that the diameter of the afferent arteriole is larger than the efferent arteriole.
The second stage is called reabsorption or, in other words, absorption in the opposite direction. It is carried out in the twisted and smooth tubules of the nephron, where, in fact, primary urine enters.
The final, third stage of urine formation is tubular secretion. The cells of the renal tubules, together with special enzymes, actively transfer toxic metabolic products from the blood capillaries into the lumen of the tubules: urea, uric acid, creatine, creatinine and others.
Normal urine relative density
The relative density of urine normally has a wide range. Moreover, the process of its formation will be determined by normally functioning kidneys. The relative density of urine tells a specialist a lot. The rate of this indicator will fluctuate many times during the day. This is due to the fact that from time to time a person eats different foods, drinks water and loses fluid through sweating, breathing and other functions. Under different conditions, the kidneys excrete urine with a density of: 1.001 - 1.040. This is considered to be normal urine density. If a healthy adult drinks a sufficient amount of water, then the relative density of urine, the norm of which is indicated above, in the morning may have the following indicators: 1.015 - 1.020. Morning urine can be very rich because no fluid enters the body at night.
The density of urine is normal if its color is straw-yellow, transparent and has a mild odor. Her reaction should range from 4 to 7.
Why is hypersthenuria dangerous?
If a person has increased urine density, this indicates that certain pathological processes are occurring in the body, which in one word are called “hypersthenuria”. Such a disease will manifest itself as an increase in edema, in particular with acute glomerulonephritis or insufficient blood circulation in the kidneys. If huge extrarenal fluid losses have occurred. This includes diarrhea, vomiting, large blood loss, burns over a large area, swelling, abdominal injuries, and intestinal obstruction. Hypersthenuria will also be indicated by the appearance in the urine of large amounts of glucose, protein, drugs and their metabolites. The cause of this disease is also toxicosis during pregnancy. If you took a test that turned out to be high (more than 1030), this result will indicate hypersthenuria. Such results should definitely be discussed with your doctor.
High urine density does not pose a great danger to human life. But it comes in two types:
- Kidney pathology, for example, nephrotic syndrome.
- Absence of primary renal pathology (glucosuria, hypovolemic conditions, in which the reabsorption of water in the tubules increases as compensation, and therefore urine concentration begins).
What does hyposthenuria indicate?
Hyposthenuria is the opposite of hypersthenuria. It is characterized by decreased urine density. The cause is acute damage to the renal tubules, diabetes insipidus, permanent renal failure or malignant hypertension.
Hyposthenuria indicates that there is a violation of the concentrating ability of the kidneys. And this, in turn, indicates renal failure. And if you are diagnosed with this disease, it is advisable to immediately contact a nephrologist who will prescribe you timely and necessary treatment.
Urine density standards for children
As discussed in this article above, urine density standards are different for each age. An adult's urine test is significantly different from a child's. It can vary in many ways, but its main difference is in the standards. The relative density of urine in a child must meet the following standards:
For a one-day-old baby, the norm is from 1.008 to 1.018;
If the baby is about six months old, the norm for him will be 1.002-1.004;
Between six months and one year of age, normal urine relative gravity ranges from 1.006 to 1.010;
Between the ages of three and five, urine density limits will range from 1.010 to 1.020;
For children who are approximately 7-8 years old, the norm is 1.008-1.022;
And those who are between 10 and 12 years old, their urine density should correspond to the norm of 1.011-1.025.
It can be very difficult for parents to collect urine from their child, especially if he is very small. But in order to determine the density of urine, at least 50 ml must be delivered to the laboratory where such an analysis is carried out.
Laboratory testing of urine is an important part of modern diagnostics. At the same time, urine analysis for specific gravity occupies one of the important places in the general study. If this parameter is deviated from the norm, this can only mean one thing - your health is not in order.
Basic Concepts
What does this mean - increased specific gravity of urine? First of all, you should understand the general concepts. So, in order to obtain an accurate value for the density of urine, you need to determine the saturation of the substances suspended in it:
- Amount of urea.
- Total uric acid content.
- Presence of creatinine.
- Content of potassium and sodium in the form of their salts.
You should know that the specific gravity of urine is directly related to the amount of urine excreted over a certain period of time. For example, urine, which is excreted especially often, has a low density. Urine in small quantities, on the contrary, has high density. The relative indicator can determine the overall health of the kidneys. Thus, a decreased parameter indicates insufficiency, and an increased one indicates hypersthenuria.
There are some standards that depend not only on age, but also on gender. For a child over 3 years old, this indicator is 1007-1017. As for mature people, the density of urine should be in the range of 1010-1020 grams per liter. In the event that the study shows a deviation from the norm, you should immediately contact an endocrinologist or nephrologist.
Diagnoses
The relative density of urine is increased. What to do? Doctors call this phenomenon hypersthenuria. A similar diagnosis is made when there is an increase, namely, a density above 1030 grams per liter. There could be a lot of reasons:
- presence of diabetes mellitus;
- dehydration due to diarrhea or vomiting;
- various toxicoses;
- inflammation of the genitourinary system.
To make the picture as complete as possible, it is worth considering the main symptoms:
- single portions of urine are significantly reduced;
- the shade of urine changes towards darker;
- weakness and apathy;
- the presence of pain in the abdomen.
It must be said that the specific gravity of urine may be underestimated. This is called hyposthenuria. As you understand, the indicators drop significantly below normal levels. The following diseases may be the causes:
- diabetes;
- maintaining a low-calorie diet;
- prolonged pyelonephritis;
- active use of diuretics;
- excessive consumption of various drinks.
Both hypersthenuria and hyposthenuria can cause dangerous consequences. It all depends on what stage the deviation from the norm is at.
How to be treated correctly
Doctors do not recommend treatment at home, since such a deviation can only be aggravated. It is best to be treated in a hospital. Constant monitoring by a doctor is required. Patients with diabetes should be particularly careful to monitor specific gravity levels. At the first hint of an increase or decrease, you should immediately contact to the doctor.
Timely diagnosis guarantees quick treatment, as well as bringing the level back to normal.
If kidney failure has been diagnosed due to low specific gravity, doctors prescribe a gentle diet, as well as the healthiest lifestyle possible. No spicy or smoked dishes. You will have to give up culinary spices. As for drug treatment, it is prescribed in the course of further research. It must be carried out under constant supervision. You may have to go to the hospital for a while.
Changes in density levels in women
In pregnant women, toxicosis occurs due to their condition. No, this is not a deviation, but a completely normal reaction of the body. So, with this toxicosis, an increase in the level of urine density may occur. At the same time, women complain of fluid retention in the body. Doctors often associate this phenomenon with gestosis. This factor is especially dangerous and can cause hypersthenuria in pregnant women.
Deviations in children
According to statistics, an increase in the specific gravity of urine in children indicates kidney disease rather than other problems in the body. Against this background, intestinal infections or poisoning can occur. They are expressed by vomiting or diarrhea. That is why at the first signs you should immediately consult a doctor. Experts have proven that the use of traditional methods does not affect these deviations in any way. The best thing to do would be to put the child in the hospital. This is necessary so that the attending physician constantly has control over the condition. Drug treatment is simply necessary. Certain medications are prescribed due to the advanced state of each individual case.
When conducting a urine test, an indicator such as . This indicator gives an idea of both the functioning of the kidneys and the activity of the brain, central nervous system, and pancreas. Its (decrease or increase) may indicate various processes occurring in the body.
The density of urine is measured in units of g/l; in a general urine test it is designated . The limits of urine density are quite wide - 1.008-1.024 g/l, and taking into account changes in conditions during the day - 1.001-1.040. Due to large fluctuations, this indicator is called the relative density of urine. It depends on the amount of substances in the urine in a dissolved or colloidal state: as well as protein, glucose and calcium.
In the morning, the specific gravity is increased because at night the liquid does not enter the body. During the day, normal density fluctuates; it will increase during heavy physical labor with increased sweating; a decrease in density occurs when eating food that causes it (melons and fruits).
When comparing the relative density of urine, the norm in children varies depending on age:
- in a newborn child - 1.02-1.022 g/l;
- up to six months of age - 1.002-1.004;
- up to one year of age - 1.006-1.01;
- up to five years of age - 1.01-1.02;
- up to eight years - 1.008-1.022;
- by the age of 12 - 1.011-1.25.
As a rule, to determine the density of urine, it is customary to measure the SG of its morning portion immediately after waking up (average specific gravity of urine for an adult healthy person is 1.015 - 1.02).
Physiological process of urine formation
In the kidneys, the contents of the blood vessels are filtered as many as two times. When blood flows through the nephrons - the renal glomeruli, its plasma is filtered through the loose walls of the tubules and enters the glomerular capsule, as a result of which the so-called plasma accumulates in it, containing all metabolic products.
Then the plasma from the capsule again enters the bloodstream through the tubules, taking with it glucose and useful nutrients, and waste products (urea, creatine, potassium and sodium salts) are released from the capsules along with the remaining liquid in the form of final, secondary urine.
Disruption of this process affects the density of the released liquid.
Changes in pathology
The density of kidney secretions can be increased (hypersthenuria) or decreased (hyposthenuria).
Hypersthenuria
An increase in urine density occurs with the appearance of protein, glucose and blood cellular elements (leukocytes and erythrocytes). High density has reasons:
- Kidney disease (acute glomerulonephritis, circulatory disorders in the kidneys - conditions in which the functioning of nephrons worsens).
- Hypervolemic conditions that increase fluid deficiency in the body (major blood loss, extensive burns, dyspeptic symptoms in the form of vomiting and diarrhea).
- Intestinal obstruction.
- Abdominal injuries.
- Severe swelling.
- Multiple myeloma, in which blood viscosity increases.
- Glucosuria is sugar in the urine due to a disorder (diabetes).
- Diseases of the genitourinary system.
- Fever.
- Use of antibiotics.
Increased urine density in women is observed with toxicosis during pregnancy. The relative density of urine increases in older people due to sclerotic processes in the vessels of the kidneys.
Diabetes mellitus is characterized by hypersthenuria in combination with polyuria (large amounts of urine). In urine, 1% sugar (glucosuria) increases its specific gravity by 0.004; 3 g/l protein () - by 0.001.
The maximum upper limit of the specific gravity of an adult is 1.028, for a child 4 years old - up to 1.025.
Hyposthenuria
Reduced relative density of urine is observed with:
- acute damage up to necrosis of the renal tubules (tubulopathy) from shock of any nature, intoxication with industrial poisons and medicinal substances, infectious diseases and some diseases of internal organs;
- malignant hypertension (renal failure);
- polyuria (excretion of large amounts of urine when taking diuretics and vasodilators);
- diabetes insipidus.
The disease “diabetes insipidus” is associated with a violation of the action of vasopressin, an antidiuretic hormone of the pituitary gland, it has the following causes:
- Violation of vasopressin synthesis in the pituitary gland.
- Impaired perception of vasopressin by the nephrons of the kidneys.
Diabetes insipidus also occurs in the form of:
- insipidal syndrome, when reabsorption processes in the kidneys are disrupted due to nervous conditions;
- transient diabetes during pregnancy, disappearing after childbirth.
The extremely low density of urine of an adult healthy person can give figures of 1.003 - 1.004.
Methods of analysis
To do an SG urine test, you must collect the test material in compliance with all the rules. To avoid distortion of indicators due to the presence of foreign impurities, urine must be collected:
- into an absolutely clean, hermetically sealed container (a jar with a wide neck);
- after thoroughly washing the genitals with soap;
- without taking the first and last portions (they may contain an admixture of leukocytes from the outer integument);
- not taking medications the day before that can change density;
- without consuming alcoholic beverages the day before.
Women should not provide urine during their menstrual period.
It is desirable that the amount of urine is about 50 ml.
Transportation of urine should only be carried out at a temperature above zero, otherwise the salts may form a dense sediment, which will affect the analysis result.
The determination of relative density is completely reliable if done after collecting urine for one and a half hours.
Progress of analysis
- The urine is placed in a cylinder. A hydrometer (urometer) is lowered into it, having a graduation from 1.000 to 1.060 - without touching the walls of the vessel. Mark the division of the scale at the level of the lower meniscus of the liquid.
If the volume of urine brought is insufficient, then it is diluted 2-3 times with water (distilled) and the density of this solution is determined with a hydrometer. The last two digits of the result are multiplied by the degree of urine dilution. Write the resulting product instead of these two digits into the result.
- If only a few drops of urine are obtained in newborn children or during catheterization in adult patients, then:
- a mixture of benzene and chloroform is poured into the cylinder;
- add 1 drop of urine to it.
- If the drop goes down to the bottom, it means that there is an increase in urine density. Add chloroform until it returns strictly to the middle of the liquid volume.
- If it floats to the surface, it means that the relative density of urine is lower than the specific gravity of the mixture. By adding benzene, the drop should be lowered to the middle of the liquid column.
A hydrometer measures the value on its scale - this result is an indicator of the specific gravity of the urine being tested.
Most urometers are designed to carry out SG analysis at an air temperature of 15ºС±3º; with a larger temperature deviation, special calculations are used, adding 0.001 when the air temperature is exceeded for every 3º and subtracting 0.001 when the air temperature decreases for every 3º.
To maintain the accuracy of the device, the urometer is constantly kept in water, wiping it before performing the analysis and thoroughly cleaning its surface from deposited salts.
1. Amount of urine
Diuresis is the volume of urine produced over a certain period of time (daily or minute diuresis).
The amount of urine delivered for general analysis (usually 150–200 ml) does not allow any conclusions to be made about disturbances in daily diuresis. The amount of urine delivered for general analysis affects only the ability to determine the specific gravity of urine(relative density).
For example, to determine the specific gravity of urine using a urometer, at least 100 ml of urine is required. When determining specific gravity using test strips, you can get by with a smaller amount of urine, but not less than 15 ml.
2. Urine color
Normal urine is yellow in color.
The saturation of the yellow color of urine depends on the concentration of substances dissolved in it. With polyuria, the dilution is greater, so the urine has a lighter color; with a decrease in diuresis, it acquires a rich yellow tint.
The color changes when taking medications (salicylates, etc.) or eating certain foods (beets, blueberries).
Pathologically changed color of urine occurs with hematuria (the type of meat slop), bilirubinemia (the color of beer), with hemoglobinuria or myoglobinuria (black color), with leukocyturia (milky white color).
3. Transparency of urine
Normally, freshly released urine is completely clear..
Turbidity of urine is due to the presence in it of a large number of cellular formations, salts, mucus, bacteria, and fat.
Cloudy urine may also indicate microhematuria, but in most cases it is a sign of infection (ie, bacteriuria). Please note: Visual urine analysis can be used as a preliminary test for the presence of a urinary tract infection in asymptomatic patients. In the course of the studies, it turned out that the sensitivity of visual examination of urine samples for diagnosing bacteriuria is 73%.
4. Urine smell
Normally, the smell of urine is mild and nonspecific..
When urine decomposes by bacteria in the air or inside the bladder, for example, in the case of cystitis, an ammonia odor appears.
Rotted urine that contains protein, blood, or pus, such as from bladder cancer, causes the urine to smell like rotten meat.
If there are ketone bodies in the urine, the urine has a fruity odor, reminiscent of the smell of rotting apples.
5. Urine reaction
Normal urine reaction is acidic.
Fluctuations in the pH of urine are determined by the composition of the diet: a meat diet causes an acidic urine reaction, a vegetable diet causes an alkaline reaction. With a mixed diet, mainly acidic metabolic products are formed, so it is believed that the urine reaction is normally acidic.
Before carrying out a general analysis, urine should be stored in a cold room and for no more than 1.5 hours. When standing in a warm room for a long time, urine decomposes, ammonia is released and the pH shifts to the alkaline side. The alkaline reaction underestimates the relative density of urine. In addition, white blood cells are quickly destroyed in alkaline urine.
An alkaline reaction of urine is characteristic of chronic urinary tract infection, and is also observed with diarrhea and vomiting.
The acidity of urine increases in feverish conditions, diabetes mellitus, tuberculosis of the kidneys or bladder, and renal failure.
6. Specific gravity of urine (relative density of urine)
Normally, the morning urine sample should have a specific gravity in the range of 1.018-1.024.
Relative density of urine (the density of urine compared with the density of water) reflects the functional ability of the kidneys to concentrate and dilute and can be used as a screening test for mass examinations of the population.
Figures of relative density of morning urine equal to or exceeding 1.018 indicate normal concentrating ability of the kidneys and eliminate the need to study it using special methods. High or low figures for the specific gravity (density) of morning urine necessarily require clarification of the reasons behind these changes.
Analysis transcript
High specific gravity of urine
The relative density of urine depends on the molecular weight of the particles dissolved in it. Protein and glucose increase the specific gravity of urine. For example, diabetes mellitus can be suspected only by one general urine test with relative density figures of 1.030 and above against the background of polyuria.
Low specific gravity of urine
The process of urine formation is regulated by the concentrating mechanism of the kidneys and the antidiuretic hormone (ADH) produced by the pituitary gland. In the presence of antidiuretic hormone, more water is absorbed, resulting in a small amount of concentrated urine. Accordingly, in the absence of antidiuretic hormone, water absorption does not occur and large volumes of diluted urine are released.
There are three main groups of reasons for a decrease in specific gravity in a general urine test:
- excess water consumption
- neurogenic diabetes insipidus
- nephrogenic diabetes insipidus
1. Excessive water intake (polydipsia) causes a decrease in the concentration of blood plasma salts. To protect itself, the body secretes large volumes of diluted urine. There is a disease called involuntary polydipsia, which, as a rule, affects women with unstable mental health. The leading signs of involuntary polydipsia are polyuria and polydipsia, low relative density in a general urine test.
2. Neurogenic diabetes insipidus- insufficient secretion of an adequate amount of antidiuretic hormone. The mechanism of the disease is the inability of the kidneys to retain water through concentrated urine. If the patient is deprived of water, diuresis almost does not decrease and dehydration develops. The relative gravity of urine may drop below 1.005.
The main causes of neurogenic diabetes insipidus:
Hypopituitarism is a failure of the pituitary gland or hypothalamus with a decrease or cessation of production of tropic hormones of the anterior pituitary gland and antidiuretic hormone.
- The most common cause of decreased specific gravity of urine is idiopathic neurogenic diabetes insipidus. Idiopathic neurogenic diabetes insipidus is most often found in young adults. Most of the underlying disorders leading to neurogenic diabetes insipidus can be identified by associated neurological or endocrinological symptoms (including cephalgia and visual field impairment or hypopituitarism).
- Another common cause of decreased specific gravity of urine is damage to the hypothalamic-pituitary region due to head trauma, neurosurgical intervention in the pituitary gland or hypothalamus. Or damage as a result of a brain tumor, thrombosis, leukemia, amyloidosis, sarcoidosis, encephalitis after an acute infection, etc.
- Taking ethyl alcohol is accompanied by reversible suppression of ADH secretion and short-term polyuria. Diuresis occurs 30-60 minutes after taking 25 g of alcohol. The volume of urine depends on the amount of alcohol taken in a single dose. Continuous use does not lead to sustained urination, despite the existence of a constant concentration of alcohol in the blood.
3. Nephrogenic diabetes insipidus- a decrease in the concentrating ability of the kidneys, despite the normal content of antidiuretic hormone in the blood.
The main causes of nephrogenic diabetes insipidus:
- The most numerous subgroup among patients with nephrogenic diabetes insipidus consists of persons with parenchymal kidney diseases (pyelonephritis, various types of nephropathies, tubulointerstitial nephritis, glomerulonephritis) and chronic renal failure.
- Metabolic disorders:
- Conn's syndrome- a combination of polyuria with arterial hypertension, muscle weakness and hypokalemia. The relative density of urine can range from 1003 to 1012).
- Hyperparathyroidism- polyuria, muscle weakness, hypercalcemia and nephrocalcinosis, osteoporosis. The relative density of urine decreases to 1002. Due to the significant content of calcium salts, urine is often white.
- Rare cases of congenital nephrogenic diabetes insipidus. The relative gravity of urine may drop below 1.005.