Composition of primary and secondary human urine. Organs of the urinary system

Urine(lat. urina) - a biological fluid produced by the kidneys and excreted from the body through the urinary tract. The formation and excretion of urine is one of the most important mechanisms for maintaining the constancy of the internal environment of the body. With urine, the end products of metabolism, excess water and salts, as well as toxic substances that enter the body from outside and are formed in it under pathological conditions, are excreted from the body. In humans, normal urine is clear, light yellow in color. Urochromes give it a yellow color. The daily normal portion is 1000-1500 cm³. The amount and composition of urine depend on environmental factors (temperature and humidity), as well as on human activity, gender, age, weight, and health status.

Chemical and microscopic analysis of urine is of great diagnostic value. In diabetes, sugar is found in the urine, in nephritis - protein, urinary cylinders. Any deviations from the normal composition of urine indicate an incorrect metabolism in the body. The chemical composition of urine is complex; it is determined by the ratio of penetration into the urine and reabsorption in different parts of the nephron of each of the chemicals filtered in the glomeruli of the kidneys from the blood and secreted in the tubules. Some substances that are practically not contained in the blood, such as ammonia, are formed in the cells of the tubules and secreted by them into the urine. Some substances filtered and secreted into the urine (creatinine, inulin, etc.) are practically not reabsorbed, the reabsorption of others (electrolytes, bases, etc.) is regulated by the needs of the body. There is also a group of substances (sugars, amino acids, etc.) that are filtered from the plasma into the primary urine, but then are normally almost completely reabsorbed in the proximal tubules, so their amount in the urine of a healthy person is negligible. These substances are called threshold, since the content of such substances in the urine normally increases significantly only when their concentration in the blood exceeds a certain level (threshold), beyond which the reabsorption of this substance is inhibited.

Normally, the amount of certain substances (sugar, protein, etc.) in the urine is so small that they are not determined by the qualitative reactions used. The detection of these substances in this way indicates an increase in their concentration in the urine and requires the exclusion of diseases in which it is observed (for example, diabetes mellitus when glycosuria is detected). The appearance of threshold substances in the urine without increasing their concentration in the blood indicates a violation of the mechanism of their reabsorption in the kidneys (genetically determined or associated with kidney pathology). According to the rate of removal of various substances from the blood with urine, i.e. according to their clearance, evaluate the urinary function of the kidneys.

The amount of urine excreted per day is called daily diuresis, its volume depends on the amount of water excreted in the urine. The value of diuresis should ensure the excretion from the body of the formed nitrogenous slags and salts coming from outside. Usually daily diuresis is 1000-1800 ml. It is assessed taking into account the density of urine and the amount of water and food taken per day (100 g of fat give about 100 ml of water when burned, 100 g of protein - about 40 ml of water, and 100 g of carbohydrates - about 60 ml of water), as well as extrarenal excretion of water (with sweat, feces, breathing). In young children, diuresis in relation to body weight is 4-6 times greater than in adults. Only by the age of 14-15 does it approach the relative value of adult diuresis (18-20 ml per 1 kg of body weight in 24 hours).

When collecting urine for a diagnostic study, certain rules must be observed. To study a single portion of urine, morning urine should be collected after a hygienic toilet in the urethral area. The study should be carried out no later than two hours after urine collection, since the presence of bacteria in it during a longer standing time of urine can significantly change its composition and properties (the reaction of urine becomes alkaline, as a result, erythrocytes, cylinders are destroyed, leukocytes dissolve). If it is impossible to quickly carry out a biochemical study, it is recommended to freeze a portion of urine at -20 °.

To study the daily volume of urine, preservatives should be placed in dishes intended for collecting urine (for example, a thymol crystal or 5 ml of a 10% solution of thymol in isopropanol per 100-150 ml of urine); when collecting urine for the determination of catecholamines, 50 ml of 10 n. hydrochloric acid solution. For microbiological studies, urine is collected in a sterile container.

Physico-chemical properties of urine urine color normally light yellow, due to physiological pigment substances (urochrome, urozein, uroerythrin, etc.). With a decrease in diuresis due to increased sweating or dry eating, daily diuresis decreases, the concentration of pigments in the urine increases and its color becomes rich yellow. Pale-colored urine is observed with polyuria. The color of urine changes qualitatively when taking certain drugs, such as analgin, a number of foods, as well as in many pathological conditions. With infectious and tumor intoxications, urine often acquires a yellow-brown color due to increased protein breakdown. Brownish-yellow (beer-colored) urine becomes in the presence of bilirubin-glucuronide (bound bilirubin) in it, which is a characteristic symptom of parenchymal and obstructive jaundice.

A significant admixture of blood gives the urine a red color of various shades and intensity (gross hematuria), which is observed with glomerulonephritis, tumors of the genitourinary organs, urolithiasis, lead intoxication; while the urine is cloudy, has the appearance of meat slops. When taking phenylin, acetylsalicylic acid, analgin, eating beets, urine has a pinkish tint, but is transparent. Macroscopically, it can be difficult to distinguish hematurin from hemoglobin- and myoglobinuria, in which the urine is also red, but in the latter two cases, when standing, it can turn brown and even black due to the formation of methemoglobin and hemosiderin. Black urine is noted with melanosarcoma, alkaptonuria. Indican gives the urine a green tint.

Urine clarity Normally, it is preserved with different saturation of its color. It can become cloudy due to the high salt content; when standing, the salts are deposited on the bottom, then the supernatant layer becomes transparent. The precipitate of urates has a brick color, phosphates - white, when the urine is heated, the precipitate of fastates disappears. Persistent turbidity that does not disappear when standing and heating urine occurs when there is an admixture of pus, a large number of bacteria, mucus, which is observed in severe inflammatory, bacterial diseases of the kidneys and urinary system. Milky-white urine becomes in the presence of lymph in the urine (chyluria). The urine of a healthy person does not foam. Foamy urine occurs when it contains protein, bile acids.

Relative density of urine, determined using a urometer, characterizes the concentration of osmotic substances in the urine (and thus the concentration function of the kidneys), of which the main ones are normally sodium and its compounds, urea. The relative density of morning urine in healthy adults is usually not lower than 1018 g/l. It increases with dry eating, extrarenal fluid loss by the body, as well as with severe glucosuria (by 4 g / l for every 10 g / l of glucose, i.e. 1% sugar), proteinuria (by 1 g / l for every 3 g / l of protein), when excreting contrast agents with urine. When the ambient temperature rises by 3°, the density of urine decreases by 1 g/ml (the urometer is calibrated at 16°). The relative density of urine decreases sharply with profuse diuresis.

For a more reliable assessment of the concentration function of the kidneys, the Zimnitsky test is used: measurement of the relative density of urine in each of eight portions collected at three-hour intervals throughout the day with arbitrary urination. At the same time, the volume of each portion of urine is determined and daytime and nighttime diuresis is calculated. Normal fluctuation of urine density during the day is 1005-1025; the highest rates of relative density are noted, as a rule, in night portions of urine of small volume. A decrease in the relative density of urine in adults to 1001-1009 (hypostenuria) is characteristic of a violation of the concentration function of the kidneys due to damage to the tubules (for example, with pyelonephritis) and for polyuria with water stress, diabetes insipidus, due to the convergence of edema.

In severe renal failure, incl. at the stage of recovery after some acute injuries of the kidneys, their ability to regulate the concentration of osmotic substances in the urine is completely lost, and therefore the relative density of urine is set at a constant level of 1010-1012, corresponding to the density of the primary urine (isostenuria). The high relative density of urine in acute glomerulonephritis, shock with oliguria is due to a sharp decrease in glomerular filtration with intact tubular reabsorption. An increase in relative density to 1035 or more requires the exclusion of glucosuria, which is characteristic of the phase of decompensation of diabetes mellitus. In newborns, the relative density of urine is about 1018, but from the 5-6th day it drops to 1002-1004 and remains so for up to 2 years. Further, it gradually rises and reaches the indicators of an adult only by 10-12 years.

Urine reaction in healthy people, it is usually slightly acidic, but depending on the diet, urine pH ranges from 5.0-7.5 (vegetable food alkalizes urine, meat acidifies it). In children, the peculiarities of the reaction of urine are that in the newborn in the first 5-6 days it is acidic, and subsequently, during the period of breastfeeding, it becomes mostly alkaline (pH 6.9-7.8); with artificial feeding, the reaction of urine is slightly acidic. The acidic reaction of urine is observed for a long time in preterm infants.

Determine the pH of urine using diagnostic indicator papers or a pH meter. With inflammatory bacterial lesions of the urinary tract, urine may undergo alkaline fermentation (especially with prolonged standing of a portion of urine prepared for analysis); while urea decomposes under the action of urease; urine becomes cloudy, its smell sharply ammoniac, alkaline reaction. The acidity of urine increases with metabolic acidosis, hypokalemic alkalosis. The composition of the resulting urinary stones depends on the acidity of the urine; uric acid stones are formed at a pH below 5.5: oxalate - at a pH of 5.5-6.0; phosphate - at pH 7.0-8.0.

The smell of urine. Urine normally has a mild specific odor. In diseases, the smell of urine changes (for example, in diabetes mellitus, urine acquires a peculiar fruity smell, reminiscent of the smell of rotting apples). To provide effective assistance to the patient during urination and for proper control of this function, it is necessary to ask the patient some questions: how often does he urinate, are there any features during urination (for example, a special posture). It is important to find out if the patient suffers from urinary incontinence. Creating habitual and comfortable conditions will allow the patient to urinate normally.

The composition of urine is very diverse, it directly depends on the consumption and production of various substances, the state of the body as a whole, and the function of the urinary tract. The main inorganic composition is represented by chemical components and nitrogen-containing compounds.

General information

Water and substances soluble in water are excreted from the body in the urine. The volume of urine and its composition depends on the composition of the diet, body weight, age, gender, physical activity and conditions such as humidity and temperature. An adult produces 0.5 to 2 liters of urine daily, of which about 95% is water. The body of an average healthy person removes 1.5 liters of urine per day. In addition to water, it contains many other substances. The chemical composition of urine includes the following components:

urea,
creatinine,
creatine,
ammonia,
urate,
amino acids.

Proteins enter the urine with a high load of pathological proteins on the glomeruli (for example, in the case of paraproteinemia), with a violation of the glomerular membrane, with diseases of the tubules of the kidneys and urinary tract. Carbohydrates in the urine are present freely in the form of glycoproteins, mucopolysaccharides and glycopeptides.

Lipids may include fatty acids, triglycerides, phospholipids, and cholesterol; lipid excretion is increased in nephrotic syndrome.

Organic constituents

The most important physiological components are represented by organic nitrogen-containing compounds. These include the following substances:

Urea (urea) is synthesized in the liver in the NH3 urea cycle, which comes from the degradation of amino acids. The secreted volume of urea depends on the amount of metabolized proteins, for example, due to the degradation of 70 g of protein, 30 g of urea per day is formed.
Uric acid is the end product of purine catabolism. In the proximal tubules of the kidneys, almost all of the filtered uric acid is absorbed, returned to the urine again through active tubular secretion, and subsequently part of it is actively resorbed again. These actions in the distal tubule may be dependent on a number of anions and drugs (competes with uric acid for transport). Only 6-12% of the filtered uric acid is finally excreted in the urine.
Creatinine is a product of muscle metabolism, spontaneously and irreversibly formed from creatine. Creatinine passing through the kidneys in the majority (90%) of the volume is filtered into the ultrafiltrate, and only 10% of it is secreted into the urinary tubules and, as a rule, is resorbed. The amount of creatinine released per day is individual and depends directly on the weight of the muscle mass and the function of individual glomeruli - thus, it can be used as a reference for the quantitative determination of other components.

The amount of secreted amino acids depends to a large extent on the quality of nutrition and the performance of the liver. Modified amino acids that are present in proteins with specialized functions, such as hydroxyproline and 3-methylhistidine, can serve as indicators of the degradation of these proteins.

Some metabolites can be conjugated with H2SO4 → sulfates, glycine, and other polar compounds. These conjugates are synthesized in a biotransformation reaction in the liver and excreted in the urine as water-soluble compounds.

Other components

Hormone metabolites (catecholamines, steroids, serotonin) also appear in the urine. Analysis of the metabolites of these hormones can provide information on the production of these hormones, for example, the determination of vanillylmandelic acid, 5-hydroxyindole, etc.

Another example is human chorionic gonadotropin (hCG, Mr = 36000). HCG is a proteohormone that is produced early in pregnancy; it circulates in the blood and, because it is a small molecule, is also present in the urine. The immunological detection of hCG in urine is the basis for most pregnancy tests.

Part of the urine is also a small amount of urobilinogen, which is produced in the intestines from bilirubin. Due to the oxidation of urobilinogen, urobilin (bile pigment) is formed.

Pathological indicators

Proteinuria is indicated by abnormal amounts of protein (particularly albumin) (i.e. greater than 0.15 g/24 hours). Proteinuria is one of the symptoms of kidney disease, which indicates damage to the glomeruli (glomeruli). Damage can be caused by mechanical or foreign substances or organisms (toxins, bacterial infections).

Glucosuria is the term for the occurrence of glucose (Glc) in the urine. Glc is filtered into the primary urine at any blood glucose level (even if hypoglycemia is present). The reabsorption increases together with an increase in glucose, but only up to certain values (blood glucose is about 10 mmol / l). Above this “renal border”, resorption does not increase, because all Glc receptor proteins are already occupied. The presence of Glc (glucosuria) increases diuresis (eg, in diabetes mellitus).

The term ketonuria refers to a condition in which ketone bodies appear in the urine (acetoacetic acid is detected). Elevated values of ketone bodies occur when fatty acids are degraded excessively (for example, during starvation or diabetes mellitus).

Inorganic components and urinary sediment

Human urine contains a significant amount of cations: Na+, K+, Ca2+, Mg2+, NH4+ and anions: Cl-, SO4-2, HCO3- and HPO4-2 and trace amounts of other ions. Secretion of ions in most cases is regulated by hormones. A number of different inorganic components are determined by the composition of the food.

Reabsorption of the above ions occurs in the tubular part of the nephron. The proximal tubules are the site of absorption of most ions (Na+, K+, Cl-, HCO3, etc.). Buffer systems are represented by phosphates and ammonia.

Urinary sediment is a term referring to the microscopic examination of urine. This is a standard examination carried out simultaneously with a chemical study. To study the sediment, urine is used no older than 2 hours after collection (after this time, the elements decay). The sediment is evaluated for the presence of blood and epithelial cells, bacteria; in addition, the presence and amount of various crystals is determined - their presence is mainly associated with insufficient hydration.

The composition of the urinary sediment can be of organic and inorganic origin. The organic part consists of cells that have 2 sources:

blood Cells,
cells of the kidney itself or excretory urinary tract.

Almost all blood cells can be present in the urine: eosinophils, erythrocytes, neutrophils, macrophages and lymphocytes (rarely). Cells of renal origin in the sediment are exfoliated epithelial cells that line the urinary tract (tubular, transitional, and squamous epithelium). The urinary sediment may contain various other cells: Trichomonas, yeast, intestinal epithelial cells, or tumor cells.

Formations known as cylinders may be present in the sediment. They are formed from a glycoprotein that protects the surface of the tubule. The glycoprotein can bind epithelial cells, leukocytes, erythrocytes and bacteria. Casts found in the urinary sediment always signify severe kidney damage.

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Elements of inorganic origin are represented by salt crystals, for example, oxalates, urates, phosphates. They are of pathological significance when found in people currently or previously treated for urolithiasis. The second group of crystals are crystals of small amino acids - cystine, leucine, tyrosine.

Thus, urine contains organic and inorganic compounds, blood cells and other elements.

The amount of urine. On average, a person excretes about 1.5 liters of urine per day. However, this figure is not constant and fluctuates over a fairly wide range. So, for example, the volume of urine excreted increases after drinking a large amount of liquid, consuming significant amounts of protein, the breakdown products of which enhance the activity of the kidneys. Conversely, urination decreases when a person consumes little liquid, when the food contains little protein, or when there is increased sweating and a significant amount of water is lost through sweat.

The intensity of urination varies throughout the day. During the day, urine is formed more intensively than at night, even if a person drinks as much water at night as during the day.

The smallest amount of urine is formed between 2 and 4 am. Decrease in urine formation at night is associated with a decrease in the activity of organs during sleep and with a slight drop in blood pressure, in connection with which pressure in the kidneys also decreases and filtration decreases.

Physical work also affects the formation of urine. With prolonged physical work, the amount of urine excreted decreases, firstly, because the capillary network of the muscles opens and blood flows to the muscles, and thereby the blood supply to the kidneys decreases, and secondly, because physical work is usually accompanied by sweating, which is also leads to a decrease in urine production.

Diuresis also increases with the ingestion of large amounts of fluids and foods that increase urination, and decreases with sweating, diarrhea and vomiting.

Polyuria- increased urine output (over 2000 ml per day) - is noted in such kidney diseases as chronic nephritis and pyelonephritis, diabetes mellitus, alimentary dystrophy, etc.

Oliguria- decreased urination (not less than 800 ml per day) is observed in such kidney diseases as acute diffuse nephritis, circulatory failure, increased tissue hydrophilicity, sodium retention in tissues, etc.

Anuria- daily urine output of 200 ml and below is usually the result of severe damage to the kidneys (parenchyma). Prolonged anuria leads to uremia, poisoning the body with urine.

Urine color. Urine is a clear, light yellow liquid. When standing, it precipitates. The resulting turbidity consists of salts and mucus.

The color of urine can range from light yellow to deep yellow. This normally depends on the content of pigments, and above all urochrome, uroerethrin, urorosein, urobelin, etc. The degree of color varies depending on the specific gravity and amount of urine excreted. Intense yellow color - high specific gravity. Pale urine often has a low specific gravity. In pathology, the color of urine can change, which is reflected in Table. 2.

Urine reaction (urine pH). With a normal mixed diet, the urine of a healthy person has a slightly acidic reaction (pH in the range of 5.0-7.0). The reaction of urine varies depending on the diet.

When eating predominantly meat food and other protein-rich substances, the urine reaction becomes acidic; vegetable food causes some alkalization, and the reaction of the urine becomes neutral or even alkaline.

A sharply acidic reaction is noted in febrile conditions, diabetes, starvation, kidney failure, etc. An alkaline reaction of urine is observed with cystitis, pyelitis, hematuria, after vomiting and diarrhea, with resorption of exudates, when taking soda, mineral water. The reaction should be determined only in native, i.e. fresh urine.

Table 1. Color of urine in health and disease (visual characteristics of urine)

Color	Norm or pathological condition	The reasons
straw yellow
Dark yellow	Congestive kidney, swelling, burns, vomiting, diarrhea	High concentration of dyes
Pale, watery	diabetes mellitus, diabetes insipidus	Low concentration of dyes
dark brown	Hemolytic anemia	Urobilinogenuria
Dark (almost black)	Acute hemolytic kidney	Hemoglobinuria
Dark (almost black)	Alcantonuria	Homogentisic acid
Dark (almost black)	Melanosarcoma
	Renal colic, renal infarction	Hematuria (fresh blood)
Type of "meat slops"	Acute nephritis	Hematuria (altered blood)
Color "beer" (greenish-brown)	Parenchymal jaundice	Bilirubinuria, urobilinogenuria
greenish yellow	Mechanical jaundice	Bilirubinuria
Whitish	Fatty degeneration and breakdown of kidney tissue
Lactic	Lymphostasis of the kidneys

Specific gravity of urine. The specific gravity of urine fluctuates depending on the amount of fluid taken. A large amount of water consumed causes a drop in specific gravity; on the contrary, when water intake is limited, the specific gravity of urine increases. On average, the specific gravity is 1015-1020 g/cm3.

For normal kidneys, there is a wide fluctuation in the specific gravity during the day, which is determined by the intake of food, water, sweating, and breathing. Low specific gravity numbers (1.005-1.012), hypoisostenuria - indicate a violation of the concentration functions of the kidneys, for example, chronic nephritis, wrinkled kidney. As a temporary phenomenon, a low specific gravity is noted with alimentary dystrophy, after heavy drinking, with a decrease in edema. A high specific gravity of urine (more than 120) is observed in acute nephritis, the formation of intracavitary exudates. Interestingly, in the case of diabetes, there is a high specific gravity of urine, even in the presence of polyuria.

Rice. 1. Crystals of salts that are part of normal urine. 1- calcium phosphate; 2 - acidic ammonium urate; 3 - calcium carbonate; 4 - uric acid; 5 - calcium oxalate.

The composition of urine. The composition of urine includes water, protein breakdown products: nitrogen-containing substances, salts and some other substances. On average, about 60 g of salts are excreted per day with urine.

Nitrogen is released mainly in the composition of urea, which accounts for approximately 90% of the nitrogen formed as a result of protein breakdown.

Normal urine does not contain protein, since, being a colloid, it cannot pass through the walls of the capillaries. The appearance of protein in the urine indicates kidney disease. Protein can appear in the urine either as a result of a pathological change in the permeability of the capillary walls, when they begin to pass protein into the urine, or during inflammatory processes in the kidneys.

However, with great physical exertion, protein can appear in the urine for a short time even in a healthy person. This is especially true for runners. The appearance of protein in the urine in this case is the result of a change in the permeability of the vascular system of the kidneys, which is associated with their increased work. Shortly after the removal of heavy physical activity, the protein in the urine of these people disappears, and normal kidney function is restored. The appearance of protein in the urine is called albuminuria. Sugar in the urine can appear in both sick and healthy people.

In sick people, the excretion of sugar in the urine is observed with diabetes. In the case of the appearance of ketone bodies in the urine of diabetic patients, a “fruity” or “apple” smell is noted.

In healthy people, sugar appears in the urine after consuming a large amount of sugar or other substances with a significant sugar content (jam, chocolate, etc.). The excretion of sugar in the urine is called glycosuria.

The normal constituents of urine are the pigments urobilin and urochrome, which give the urine its characteristic color. Urine pigments are formed in the intestines and kidneys from bile pigments, which in turn are formed from the breakdown products of hemoglobin.

The appearance of blood in the urine, or hematuria, is observed; with hemorrhages in the region of the kidneys or urinary organs.

The erythrocytes found in the urine can be unchanged (that is, containing hemoglobin) and changed, free from hemoglobin, having the form of single-circuit or double-circuit wheels. In the normal urine of adults and children, a small amount of red blood cells may be noted. If the urine is red, then this condition is defined as gross hematuria. With microhematuria, erythrocytes are detected only microscopically. Renal hematuria is associated with organic kidney damage - these are acute and chronic nephritis, hemorrhagic diathesis, malignant neoplasms. Renal hematuria can be with heavy physical exertion. Extrarenal hematuria develops in diseases of the bladder, pelvis, ureters and injuries.

An increase in the number of leukocytes in the urine indicates inflammatory processes in the kidneys or urinary tract (kidney tuberculosis, pyelitis, cystitis, pyelonephritis, etc.).

Cells of the renal epithelium are not found in normal urine, they appear with nephritis, nephrosis, intoxication, feverish conditions and infectious diseases.

The cylinders that are found in the urine are protein cell formations of tubular origin, shaped like cylinders. There are hyaline, granular, waxy, epithelial, erythrocyte, pigment, leukocyte cylinders. The appearance of a large number of different cylinders (cylindruria) is observed with organic lesions of the kidneys (nephritis, nephrosis), with infectious diseases, congestive kidney, with acidosis.

The daily amount of urine and its composition are variable and depend on the time of day and year, external temperature, the amount of water drunk and food composition, the level of sweating, muscle work and other conditions. During sleep at night - from 2 to 4 hours diuresis is the smallest, and from 12 to 16 hours of the day - the largest. In adult men, daily diuresis reaches an average of 1.0-1.5 dm3, and in women - 0.9-1.2 dmg. These fluctuations in the daily amount of urine reflect changes in metabolic rate.

During the day, the composition of urine also changes: nighttime is darker and more concentrated than daytime. In summer, on hot days, the amount of urine decreases and it becomes more concentrated. Taking large amounts of water and sodium chloride increases diuresis. Most of all, the composition of urine is influenced by the composition of food and the full and hungry state of the body, since urination is the final stage of metabolism, and the composition of urine is a mirror of metabolism. Short-term intense muscular work increases diuresis, which depends mainly on the increase in total blood pressure during work. Prolonged intensive muscular work reduces diuresis, which depends on a long-term decrease in the blood supply to the kidneys due to the outflow of blood to the muscles and on increased sweating.

In changing the amount and composition of urine during muscular work and physical exercises, an essential role belongs to reflexes from working muscles to the kidneys.

Urine is an aqueous solution of various substances in different concentrations that do not correspond to ordinary aqueous solutions. The specific gravity of adult urine is 1.010-1.025, pH = 4.7-6.5. The degree of slightly acid reaction of urine varies depending on the appearance in the blood and excretion of excess alkalis or acids from the body. During muscular work, due to the accumulation of phosphoric, lactic and carbonic acids in the blood, the urine becomes more acidic, during gastric digestion, due to a shift in the reaction of the blood to the alkaline side as a result of the secretion of acidic gastric juice, it becomes more alkaline. The reaction of urine becomes neutral and even slightly alkaline with plant foods containing many alkalis.

In a healthy person, there is no unsplit protein in the urine; a small amount in the primary urine is rapidly reabsorbed. After prolonged intensive muscular work, protein temporarily appears in the urine as a result of an increase in the permeability of the capillaries of the Malpighian glomeruli and capsules and a decrease in its reabsorption in the tubules. Children and teenagers should not do heavy muscular work that causes protein in the urine.

Sugar (glucose) in a healthy person is usually not contained in the urine and appears temporarily with its excess content in the blood. The appearance of glucose in the urine is referred to as food glucosuria.

Comparison of the composition of blood and urine allows us to present the results of the work of the kidneys in maintaining the relative constancy of the composition of the blood.

Urine is not just a biological fluid, but also a kind of indicator that signals any changes that occur in the body. The main organ that is responsible for the production, excretion and composition of human urine is the kidneys. Urination or diuresis is the most important process, without which it is impossible to maintain the normal functioning of the body, because metabolic products, salts and toxins are excreted along with urine.

For a day, in an adult, the blood is cleared by the kidneys about 300 times, after which the waste is excreted through the urethra. It is generally accepted that after filtration, 1.2 to 2 liters of liquid should be released. Its quantity and indicators are determined by a number of factors:

climatic conditions;
physical activity;
age, weight;
consumed food.

Any deviations from the norm (both up and down) is a reason to consult a doctor for an additional examination.

In order for the tests to be reliable, it is recommended to adhere to the rules for collecting urine. The first morning portion, which is collected after thorough washing of the external genital organs, is subject to research. A single container must be delivered to the laboratory within 2 hours, otherwise the chemical composition of the urine may change.

Physical properties of urine

The physical characteristics of urine include:

Density or specific gravity (determined with a urometer). With the use of water in large volumes, the amount of urine increases, respectively, its density becomes less. The norm is in the range from 1.002 to 1.040 g / ml. After profuse sweating, the density can reach the upper limit of the norm, however, if this is due to sports training, you should not worry.
Acidity (pH). This indicator can change its value depending on the food consumed: plant foods increase, and meat products reduce the level of alkali in the urine. The average number is 5.5-7. High acidity is the first symptom of pyelonephritis, cystitis, thyroid dysfunction or kidney failure. An acid reaction is typical for newborns in the first days of life.
Color and smell. As a rule, in healthy people, urine is colored in a moderately yellow hue and does not have a strong odor. Density also affects color - the higher it is, the brighter the color pigment is expressed. If the urine has acquired a reddish tint, this is a possible sign of diseases such as glomerulonephritis or porphyria. Urine that has the color of dark beer indicates liver disease (hepatitis or jaundice). And urination with the smell of ammonia indicates an acute inflammatory process of the bladder (cystitis).

PLEASE NOTE: Eating foods such as beets or carrots, or taking certain medications (such as aspirin) the day before your test can affect the color of your urine.

What is in urine?

The chemical composition of the urine of a healthy person is diverse and inconsistent; in total, almost 150 different compounds of an organic and inorganic nature were found in this waste product.

The bulk of the total mass is occupied by urea (normally up to 35 g / day) - a breakdown product of proteins in the body. Also, urine is considered normal in the presence of such substances as:

uric acid (up to 0.7 g); this compound can cause the formation of stones in the genitourinary system;
creatinine (up to 36 mg);
ammonia (up to 57);
sulfates (up to 83 mg) and phosphates (up to 127 mg);
as well as elements known in chemistry - sodium, potassium, magnesium and calcium.

organic sediment

Secondary urine may contain blood cells, leukocytes and epithelium, which together form an organic sediment.

Women contain from 1 to 3 red blood cells, and their presence in men is a clear sign of kidney or genitourinary system disease.

The number of leukocytes normally should not exceed 7 for men and 10 for women. An increased level of leukocytes (from 60) is accompanied by cloudy urine, which acquires an unpleasant smell of rot and a greenish tint. If leukoceturia is bacterial in nature, this indicates a current infectious disease.

GOOD TO KNOW: When shaking the container, the urine should not foam. The formation of foam occurs when there is a protein or bile acid in the composition.

Pathological indicators of urine

In the composition of urine, components such as protein, blood, sugar, and others should normally be absent. They are a pathology and signal certain violations in the work of the body.

For example, if a certain amount of glucose (over 10 g) was detected during laboratory diagnostics, this is an indicator of glycosuria, which is a symptom of diabetes mellitus. Also, in this case, diseases of the kidneys, liver and pancreas should not be excluded.

USEFUL TO KNOW: For reliable results of the study of urine for sugar, it is collected during the day, skipping the first urination.

In acute inflammation of the genitourinary system, erythrocytes (blood cells) may be present in the urine. This pathology is sometimes observed in athletes after injuries of the urinary organs.

If a lot of ketone bodies come out with urine, this means that the body uses fat reserves instead of carbohydrates to produce energy. This phenomenon can be observed with diabetes, exhausting physical training and starvation.

Inflammatory processes are also evidenced by cylinders or cubic particles of the epithelium, which are normally absent in human urine.

With diseases of the kidneys or heart, the patient may experience proteinuria - an increase in the amount of protein in the urine. This substance is almost always associated with violations of the body. In adults, the amount of protein should not exceed 0.033 g / l, and in infants - from 30 to 50 mg. Sometimes this indicator is overestimated under the influence of elevated temperature or after physical exertion. If during repeated analyzes in the urine protein is found in the amount of:

150-500 mg / day - this indicates, ropatey, acute or chronic glomerulonephritis;
500-2000 mg - possible manifestation of post-streptococcal glomerulonephritis in the acute stage;
over 2000 mg - the patient has a non-rotic syndrome.

Such components as bilirubin and urobilinogen should not be present in the analyzes. They, as a rule, color urine in a rich yellow or brown color, and speak of problems with the liver or.

So, the composition of urine, as well as its physico-chemical properties, can change under the influence of various diseases. In any case, only a doctor should establish the correct diagnosis. It is worth regularly monitoring any changes in the urine - in a timely manner to detect and prevent violations in the body.