Renal clearance. Calculation methods for determining the CF value

The renal clearance of a substance B is equal to the ratio of the rate of excretion of this substance in the urine to its concentration in the blood plasma:

C in = ---------- (ml/min), (1)

where Sv is clearance, Mv and Pv are the content of blood in urine (M) and plasma (P), respectively, V is the volume of urine formed in 1 minute.

By simply transforming equation (1), we obtain Sv x Pv = Mv x V (amount of substance/time) (2)

It can be seen from this that the formula for calculating clearance is derived based on equating the amount of a substance removed from the blood plasma per unit of time (St. Pv) and the amount of substance excreted in the urine during the same time (Mv. V). In other words, renal clearance reflects the rate of plasma clearance of a particular substance. This indicator is measured in ml/min, and therefore can be considered as the “volumetric rate of clearance” of a certain substance from the plasma.

Thus, the clearance of a substance is quantitatively equal to the volume of plasma that is completely cleared of this substance by the kidneys in 1 minute.

This definition is quite convenient for describing equation (1), but it accurately reflects the actual state of affairs only in two cases. The fact is that usually there is no complete cleansing of any part of the renal bloodstream; on the contrary, partial purification of all blood passing through the kidneys occurs. At the same time, there are two substances from which a certain volume of plasma is actually completely cleared. These two exceptions are of particular relevance to the urinary hypothesis and provide the basis for the overall assessment of renal function.

1. Inulin clearance corresponds to the glomerular filtration rate, i.e. part of the total renal plasma flow filtered into the urinary tubules.

2. The clearance of paraaminohippuric acid (PAH) almost reaches the maximum possible value, i.e. almost equal to the total renal plasma flow.

Homeostatic functions of the kidneys

The kidneys are involved in the regulation of:

1. Volume of blood and other internal fluids.

2. Consistency of osmotic pressure of blood, plasma, lymph and other body fluids.

3. Ionic composition of internal fluids and ionic balance of the body (Na +, K +, Cl _, P _, Ca +).

4. In maintaining acid-base balance.

5. Excretion of excess organic substances coming from food or formed during metabolism (glucose, amino acids).

6. Excretion of end products of nitrogen metabolism and foreign substances.

7. In maintaining blood pressure (renin-angiotensin-aldosterone system).

8. Secretion of enzymes and physiologically active substances (renin, bradykinin, prostaglandins, urokinase, vitamin D 3).

9. Participate in the regulation of erythropoiesis (erythropoietin).

10 In the kidneys, urokinase is synthesized, which is involved in fibrinolysis.

Thus, the kidneys are an organ involved in ensuring the constancy of the basic physicochemical constants of blood and other fluids of the internal environment of the body, circulatory homeostasis, and regulation of the metabolism of various organic substances.

CLEARANCE in medicine(English) clearance) - the rate of purification of blood plasma, other media or body tissues from any substance in the process of its biotransformation, redistribution in the body and (or) excretion from the body.

The concept of “clearance” in medicine was formulated in 1929 by D. D. Van Slyke et al. applied only to the purification of plasma from substances secreted by the kidneys, in particular from urea. In this case, K. was defined as the degree of purification of any substance from the blood plasma that passed through the kidneys in 1 minute. In subsequent years, due to the widespread use of indicator dyes and radioactive isotopes in diagnostics, the concept of “clearance” began to be used to denote not only the indicator of plasma purification, but also the rate of decrease of the indicator substance from the studied volume of any tissue or organ. However, the traditional use of the concept of “clearance” (in relation to plasma purification) is the most stable.

In current terminology, the purification of plasma from any substance is designated as K. of this substance, for example. K. inulin, K. creatinine. In formulas, K. is denoted by the symbol C, next to the Crimea the substance is abbreviated, for example. Cin - K. inulin. Depending on the role of which organ in the purification of plasma is studied, they speak of renal K., hepatic K., etc. There is also the concept of general, or total plasma K. (Pg), the value of which characterizes the rate of plasma purification from substances regardless of purification mechanisms (excretion by excretory organs, biotransformation with loss of original properties, etc.). Having simultaneously determined the total plasmatic K. and the intensity of purification from this substance by the kidney or liver, the role of these organs in the total plasmatic K. was shown, for example, the leading role of the kidneys in the purification of plasma from penicillin, inulin, para-aminohippurate (PAH) and the leading role liver in K. bromsulfophthalein and rose bengal.

To determine total plasma K., the indicator substance is injected once into a vein and several blood samples are collected at certain time intervals to study the dynamics of the concentration of the injected substance in the plasma. A drop in the concentration of certain substances in the blood, e.g. PAG occurs exponentially (over equal periods of time, the concentration decreases by the same relative part of the original value), other substances, for example, bromosulfophthalein, ethanol, cythembene, - in the form of a linear dependence (the concentration decreases by the same absolute value over equal time intervals), and Some substances have a curve of decreasing concentration in the blood in the form of an abnormal function. Depending on the nature of the drop in the concentration of a substance in the blood plasma, various formulas are used to calculate K.

Total plasmatic K. is calculated by the formula

where I is the amount of the substance introduced into the blood, S is the area under the curve of the concentration of the substance in the plasma (along the ordinate axis) during the study (on the abscissa axis). If the concentration curve is exponential, in order not to determine the area under it, use the formula

Page = I*0.693/P 0 T 1/2

where P 0 is the initial concentration in plasma in mg/ml, T 1/2 is the time (in minutes or hours) to reduce the concentration of the substance in plasma by 2 times, I is the amount of the administered substance.

The role of individual organs in the blood flow of a substance can be determined by the difference in the concentrations of this substance in the plasma of the blood flowing to the organ and the blood flowing from it. This difference can also be judged by the difference in concentrations of the substance in plasma and in secreted fluids (for excretory organs). K. of a substance due to the excretory function is determined by the general formula

where V is the volume of secretion (excretion) obtained per unit of time (usually in ml/min), K is the concentration of the substance, i.e. the amount in 1 ml of secretion (for example, urine, bile), P is the concentration of the substance in plasma . Methodologically, it is important that to determine total plasmatic K. a single injection of the substance is performed; to measure organ, in particular renal, K., continuous infusion is preferable in order to maintain the concentration of the test substance in plasma at a constant level.

Clinical significance of clearance tests

Clearance tests are most widely used and developed in the study of renal functions. Using clearance tests, renal plasma flow, glomerular filtration, reabsorption and secretion are determined (see Kidneys). In this case, differences in the renal K. of different substances are used. The determination of renal plasma flow is based on the measurement of K. cardiotrust, PAG, or hippuron, from which the blood plasma is completely cleared during a single passage through the renal cortex. To measure glomerular filtration, the K of substances that are filtered but not secreted or reabsorbed (inulin, sodium thiosulfate, polyethylene glycol 1000, mannitol) is determined. The result obtained is reduced to a standard body surface (1.73 m2). Inulin K in humans is 127, and PAG clearance is 624 ml/min per 1.73 m2. Since long-term infusion into a vein of solutions of inulin and other substances used to determine glomerular filtration is complex, in the clinic its measurement by K. of endogenous creatinine gives quite satisfactory results. When a substance is excreted only by the kidney, it is possible to determine its K. without taking urine; if the rate of administration of the substance is regulated so that its concentration in the plasma is maintained at a constant level, then the amount of the administered substance is equal to its K.

Since the determination of renal K. is associated with the study of the concentration of the test substance in the urine, it is impossible not to take into account the transport of water in the kidneys, as well as their ability not only to excrete, but also to retain certain substances in the body. In the latter case, the concentration of the substance in the urine will be less than in the blood plasma. To determine whether excretion of a given substance occurs by the kidney, use the calculation of K. using the formula

C = V(U - P)/P,

where U is the concentration of the substance in the urine. For substances whose concentration in urine is lower than in plasma, the resulting K value will be negative; this will indicate that the substance is retained in the plasma and excess water is released. The concept of positive and negative K. is important for characterizing the osmo- and ion-regulatory functions of the kidneys.

The use of radioactive isotopes as test substances has significantly expanded the capabilities of clearance tests in wedge, practice and increased their wedge, significance. The effective renal plasma flow and blood flow are determined from the decay curve of radioactivity over the heart. Substances that are used to determine glomerular filtration, but have radioactive isotopes in the molecule (inulin-131 I, EDTA-51 Cr, EDTA-169 Yb), allow testing without urine collection, which makes it possible to determine glomerular filtration with low diuresis . Isotope renography allows one to evaluate the function and condition of the kidneys in various diseases, the evacuation function of the upper urinary tract; it is used to monitor the condition and function of the transplanted kidney (see Radioisotope renography).

Clearance tests in hepatology are used to study the absorption and excretory function of the liver (see). At the same time, substances are introduced into the body that are absorbed by the liver and excreted with bile (bilirubin, bromsulfalein, azorubine-S, rose bengal, wofaverdin, ueverdin, etc.). More often they use bromosulfophthalein test (see) and wofaverdine test (see).

To determine hepatic parenchymal K., pink Bengal, labeled with 131I, is used, which has pronounced hepatotropism. K. curves are processed using an exponential equation, calculating the half-life of elimination, the time of the maximum level of radiation over the liver, and the time of appearance of the drug in the intestine. In liver diseases, the rate and extent of absorption and the degree of absorption and excretion of paint decrease: with damage to polygonal cells, the absorption process suffers to a greater extent, and with inflammation, and especially disruption of the bile ducts, the excretory function. It is especially important to compare the clearance rates of the blood and liver from the drug. If the outflow of bile is obstructed, a normal or little-changed decrease in the drug from the blood is observed with its slow removal from the liver; simultaneous impairment of rose bengal absorption suggests parenchymal damage. With the help of clearance tests, it is possible to identify anicteric forms of viral hepatitis, prognostic assessment of the recovery period after acute viral hepatitis, the degree of damage and the dynamics of the process in chronic and liver diseases.

To study regional blood flow, the so-called method is used. tissue clearance - the rate of elimination of isotopes 133Xe, 85Kr, albumin labeled with 131I, etc. from the tissue (organ) under study, in which a drug depot has been created.

The prospect of using clearance tests in a wedge, research is steadily expanding. With their help, they study the metabolism of a number of substances, for example, albumin, the lifespan of red blood cells, the production of bilirubin, biol, the hormone cycle, the rate of consumption of profactors and factors of the coagulation and anticoagulation system of the blood.

The determination of plasmatic K. is used in the study of the pharmacokinetics of drugs, to study the absorption of drugs from gastrointestinal tract. tract, their distribution in the body, the role of various organs in their release or destruction. In addition, K. is used to judge the effectiveness of cleansing the body of endogenous and exogenous substances when using such treatment methods as hemodialysis (see), peritoneal dialysis (see), hemosorption (see), lymphosorption (see), plasmapheresis (see). see), metabolic replacement of blood.

Bibliography: Hexmosorption, ed. Yu. M. Lopukhina, M., 1977; Graf n e black grouse J. et al. The importance of plasma clearance in the study of the kinetics of antibiotics, Antibiotics, vol. 5, no. 3, p. 56, 1960; Lopukhin Yu. M. and M o-lodenkov M. N. Hemosorption, M., 1978; Fundamentals of hepatology, ed. A.F. Bluger, p. 116, Riga, 1975; Shyuk O. Functional study of the kidneys, trans. from Czech., Prague, 1975, bibliogr.; I r about sh e in with to and y A. Ya. Clinical nephrology, L., 1971; Koi-shanp our E. Renal physiology, Philadelphia, 1976.

Yu. V. Natochin, M. E. Semendyaeva.

Nephrosis is a kidney disease that affects the nephron tubules. The nephron is the main structural unit of the kidney; there are at least 1 million of them. They act as a filter - they cleanse the blood and produce urine, which removes waste from the body.

Only 35% of all nephrons are involved. The rest form a reserve so that in the event of an emergency the kidneys continue to perform their functions. Nephrons do not have the ability to regenerate, so after 40 years the body loses approximately 1% of their number every year. By the age of 80, this loss is already 40%, but it does not affect kidney function. But the loss of over 75% of nephrons has serious consequences, including death.

Causes and types of disease

The causes of the disease are as follows:

• infectious diseases.
• Renal pathologies: glomerulonephritis, pyelonephritis and kidney prolapse.
• A genetic disorder of how the body breaks down proteins.
• Poisoning by toxins or chemicals taken orally or by inhaling vapors. Among the toxins there are special substances that damage the kidneys - nephrotoxins. These include, for example, poisonous mushrooms, acetic acid, ethylene glycol, a number of medications, and heavy metals.
• Transfusion of incompatible blood.
• Oncopathology.
• Deep skin lesions accompanied by infections.
• Systemic diseases (sarcoidosis, rheumatism, amyloidosis, syphilis).

Depending on the cause, there are 4 types of disease, in which degeneration of the renal tubules occurs with disruption of their functions.

Kidney amyloidosis

Amyloid nephrosis occurs when protein metabolism is disrupted. This occurs with a genetic pathology of protein synthesis (primary amyloidosis) or against the background of long-term infectious diseases (syphilis, tuberculosis, osteomyelitis).

Under the influence of infection, altered protein molecules are synthesized. In response, autoimmune processes occur, resulting in the formation of amyloid, a modified protein concentrate. It affects the vessels of the nephron glomeruli, where blood plasma is purified.

Necronephrosis

With necrotizing nephrosis, the blood supply to the organ is disrupted, which causes the structure of the tubular epithelium to be destroyed.

The cause is exposure to infections or toxins. Kidney failure develops:

• fluid filtration is impaired;
• the amount of urine decreases to a minimum.

This increases the concentration of toxins, which increase pathology in the renal tubule.

Post-transfusion and febrile nephrosis

Post-transfusion nephrosis occurs due to careless blood transfusion. When the blood of the donor and recipient is incompatible, red blood cells begin to break down, causing shock.

Febrile nephrosis accompanies infectious diseases and is characterized by an increase in protein in the urine. It goes away on its own when the infection subsides.

Myoglobinuric nephrosis

The cause of this type of disease is alcoholism or heroin addiction. Under the influence of toxins, protein breakdown occurs in muscle tissue. This increases the level of myoglobin pigment, causing the urine to become reddish-brown in color.

Myoglobinuria develops, which causes damage to the renal tubules.

Lipoid nephrosis

Separately, it is necessary to say about lipoid nephrosis of the kidneys - what it is, how it manifests itself and who most often suffers from it. This type of disease is rare and leads to slight degeneration of the renal tubules. Occurs after viral and bacterial infections. Recent studies show that autoimmune processes are involved in the development of lipoid nephrosis.

Children and adolescents, especially boys, suffer from lipoid nephrosis. Most often it is diagnosed at 2–4 years of age. The exact cause of this nephrosis has not been established. One of the hypotheses is that the abdominal cavity is not fully developed and the body’s defenses are not fully formed. With age, relapses of the disease occur less frequently, and when remission occurs, children lead a normal lifestyle for healthy children.

Symptoms

Symptoms and treatment of nephrosis depend on the form of the disease. The main symptom of the disease is swelling. They are associated with an increase in the permeability of the walls of the nephron tubules for plasma proteins and impaired protein metabolism. Proteins are excreted in the urine, which reduces their amount in the blood. This leads to a decrease in osmotic pressure in the blood vessels, and fluid enters the intercellular space.

In the early stages, the signs of the disease are weak, which does not contribute to timely diagnosis. But after laboratory tests and examination of the patient, the disease is diagnosed without difficulty.

With different types of kidney nephrosis, the symptoms, in addition to the general ones, have characteristic differences:

• Lipoid: mild swelling on the face (pasty), accumulation of fluid in the peritoneum and pleural cavity, lower back pain, fatigue, weakness and poor appetite.
• Amyloid: fever, muscle pain, abnormalities in the liver and spleen, protein in the urine.
• Post-transfusion: sharp increase in body temperature, severe chills. Bronchospasms make breathing difficult, headaches and lumbar pain appear, and blood pressure drops. The skin, initially pale, becomes icteric due to the enlargement of the liver. Shock and involuntary urination or bowel movements may occur.
• Necrotic: acute onset with pronounced signs of intoxication and shock kidney syndrome, protein in the urine.

Common symptoms of nephrosis include swelling, decreased urine output (oliguria), weakness, and darkening of the urine color.

There are 4 stages of swelling:

• I – legs swell;
• II – swelling spreads to the genitals, lower abdomen and lower back;
• III – swelling of the neck and face is added;
• IV – generalized edema turns into a progressive form. Liquid accumulates not only under the skin, but in organs and cavities.

An important symptom for identifying the disease in the early stages is a change in laboratory parameters of urine, its darkening, and the appearance of protein.

Treatment

If edema appears, you should immediately contact a urologist, because nephrosis is easier to prevent than to cure. Nephrons are not repaired or replenished. Necrotizing nephrosis is more curable, provided that you consult a doctor in a timely manner and follow all prescriptions, although in severe cases of the acute phase the patient may die from shock or anuria.

Amyloidosis is less treatable. Positive dynamics consist only in a speedy transition to the remission stage and an increase in its duration. An immediate visit to a urologist is the path to success.

The treatment of nephrosis is based on 3 cornerstones:

• eliminating the main cause of the disease;
• fight against edema;
• normalization of protein in the blood.

Treatment is carried out in a complex:

• drug and vitamin therapy;
• Spa treatment;
• diet.

Drug therapy is prescribed by the doctor, based on the type of disease and stage - acute or chronic. So, with lipoid nephrosis, the main task is to eliminate the source of infection. For this purpose, antibacterial drugs are prescribed. Treatment of nephronecrosis, first of all, requires removing toxins from the body and carrying out anti-shock measures. In the acute stage of amyloid nephrosis, blood transfusion is possible.

For any form of the disease, diuretics are prescribed to combat edema. If they are ineffective, drainage needles are inserted under the skin to drain the fluid. Additionally, decoctions of diuretic herbs are taken. A strict diet is a maintenance treatment. It cannot be neglected, but it is adhered to only during periods of exacerbation. It includes the following:

• Reducing salt and fluid intake.
• Containing a large amount of protein in food to replenish its loss in urine. If the disease is complicated by glomerulonephritis, then the diet should be high in calories from fats and carbohydrates, and the amount of protein only covers its loss.
• Eating foods rich in vitamins.

Hypokalemia often develops with nephrosis. Then potassium-containing products and pharmaceutical drugs are prescribed. When remission occurs, the patient is advised to eat a variety of foods containing essential nutrients, vitamins and minerals. Regular spa treatment is very useful.

Prevention

First of all, it’s proper nutrition, the absence of bad habits, and improving immunity. To avoid injury or bruises to the kidneys, you need to be careful when engaging in sports or strenuous physical activity. You should not constantly wear compressive underwear and clothing or leave your lower back bare. Colds and infectious diseases should be treated on time.

The regime plays an important role - regular, balanced meals, 8 hours of sleep, walks in the fresh air, taking vitamins - this is what strengthens the body's defenses. Water regime is important - for normal kidney function, the daily need for clean natural water is at least 2 liters.

Kidney diseases in children

Kidney disease in children is common. They suffer more often than adults; the cause of such disorders is weak immunity. In addition, children suffer more severely from any inflammation, with a number of complications. It is important to recognize the disease at an early stage so that the disease does not become chronic.

• Main reasons
• Congenital pathologies
• Hydronephrosis
• Megaureter
• Multicystic
• Polycystic
• Violation of the structure of the organ
• Acquired diseases
• Pyelonephritis
• Glomerulonephritis
• Cystic formations
• Dilated pelvis
• Kidney failure
• Nephroptosis
• Signs
• Diagnostics
• Therapy
• Prevention

Main reasons

The genitourinary system is formed during the intrauterine development of the fetus. After birth, the paired organ continues to grow. After a year and a half? In children, the kidney is fully formed and of normal size. Kidney disease is often diagnosed in the first years of life, but sometimes abnormalities are also detected in adolescents.

The causes of the development of the disease are congenital or acquired. The first include defects that appeared during intrauterine development. The cause of such anomalies is the mother’s illnesses during pregnancy or her poor lifestyle.

In children, kidney disease can result from:

• Past or chronic pathologies. Sore throat, tonsillitis, and diabetes mellitus can provoke disorders.
• Food, drink. A proper diet plays a huge role in the development and functioning of the kidneys. It is important to pay attention to the amount of fluid consumed; a normal volume of water prevents pathogenic bacteria from depositing in the ducts.

• The body's defenses. Kidney disease in children is often diagnosed when the immune system is weakened.
• Hygiene. It affects the condition of the genitourinary system in children and proper care; in the absence of regular washing, bacteria penetrate the kidneys and provoke inflammation.
• Hypothermia. A common cause of kidney disease in children is cold kidneys; girls are most susceptible due to their anatomical features.

Congenital pathologies

The cause of kidney disease is most often congenital anomalies. Such deviations are the result of an incorrect lifestyle of the expectant mother, past infections, and hypothermia. These processes contribute to the development of kidney inflammation in a pregnant woman, which passes to the fetus.

Hydronephrosis

This disease is caused by stagnation of urine in the calyces of the kidney. The process occurs as a result of abnormalities in the development of the ureter or lumen. These features are determined during examination of the fetus from the fourth month of intrauterine development. After birth, surgery may be required to normalize the functioning of the urinary organs.

Megaureter

The disease occurs in the presence of reflux (vesicoureteral). In this case, urine returns from the bladder. The cause is an abnormal development of the valve or underdevelopment of the baby’s nervous system. The optimal solution is surgery; special gels are used as an alternative treatment.

Multicystic

This disease occurs in the fetus under the influence of toxic substances taken by the mother or as a result of genetic disorders. With this disease, a change in the structure of the kidney tissue occurs, and the organ is unable to perform its functions.

If there is a formation that does not exert pressure and does not interfere with the normal functioning of the kidneys, the cyst is left and monitored. Otherwise, surgical intervention is required.

Polycystic

The cause of the disease is disorders at the genetic level. At the same time, the kidneys cope with their functions. You can live with this disease, but it is possible that such a disorder can cause kidney failure. Severe abnormalities will require dialysis or a donor kidney transplant. With polycystic disease, it is important to adhere to a healthy lifestyle.

Violation of the structure of the organ

If there are anomalies that arose during the development of the fetus, as the child grows older, problems may arise in the functioning of the organ. Such disorders include duplication of the kidneys and ureter, horseshoe-shaped structure. For such changes, surgery is indicated; the optimal period is up to 1 year.

Acquired diseases

As children grow up, kidney pathologies are possible, which arise for various reasons.

Pyelonephritis

It is characterized by inflammation that appears against the background of hypothermia or as a result of past illnesses. Sometimes it becomes a consequence of surgery performed on the urinary organs. With improper treatment, there is a risk of transition to the chronic stage. If therapy is started immediately, the disease can be quickly cured. Antibiotics are most often used to get rid of inflammation.

Glomerulonephritis

The glomerulus, which is responsible for filtration, suffers. The disease can occur in acute or chronic form. Develops as a result of previous diseases, such as streptococcal infection, tonsillitis, scarlet fever.

Cystic formations

If there are growths on the kidneys, their nature is of great importance. Cysts are usually benign, but there is a possibility of becoming malignant. Therefore, children with kidney cysts are seen by a doctor. The cause of the development of this disease is the proliferation of epithelial cells. If the growth increases in volume, surgery is required.

Dilated pelvis

It is a consequence of reflux, in which the reverse release of urine occurs. It may be the result of an abnormal structure of the organ’s vessels, which affects the structure of the kidney tissue.

Immediately after the baby is born, experts recommend performing an ultrasound of the kidneys. This allows you to identify disorders at an early stage and make decisions to prevent further development of the disease.

Kidney failure

With such a pathology, the paired organ is not able to perform its functions. This contributes to electrolyte imbalance; uric acid accumulates in the patient’s blood. Such a pathology can lead to organ failure, which entails the most severe consequences, including death. Therefore, such a disease cannot be ignored.

Renal failure occurs against the background of pyelonephritis, abnormal organ structure, and occurs in a chronic form. The cause of the acute stage may be the influence of toxic substances, which occurs against the background of an overdose of medications.

Nephroptosis

It is caused by a structural anomaly in children, in which the kidney is not sufficiently fixed. The organ is mobile, can rotate around its axis, and with such movement the vessels suffer, which provokes disruption of normal blood circulation.

ICD

The appearance of urolithiasis in children is the result of changes in the water-salt balance. Pathology occurs due to insufficient fluid intake or poor nutrition. Drinking plenty of fluids helps remove salts and prevents the formation of stones. The disease also occurs against the background of deficiency, when mineral metabolism is impaired. It is treated by laser exposure or surgery.

Signs

Symptoms of kidney disease in children differ depending on the type and severity of the pathology. If developmental anomalies began during the gestation stage, deviations can be determined by the following signs:

• abdominal enlargement;
• violation of urine color;
• urination with reduced pressure;
• low-grade fever;
• vomit;
• loose stool.

Kidney disease in newborns can cause yellowing of the skin as a result of metabolic disorders. A particularly dangerous sign is the absence of urine - this is a reason for immediate hospitalization. Convulsions and restless behavior during deurinization also require medical attention.

Signs of kidney disease in older children may appear in a latent form, making early diagnosis difficult. But there are characteristic signs that cannot be ignored:

• painful urination;
• changes in the composition and color of urine;
• presence of “flakes”;
• smell of acetone;
• pain in the lower back and abdominal cavity.

In the presence of inflammation, an increase in temperature is observed. Children refuse to eat and have dry mouth. In the morning, swelling on the face is noticeable. Such symptoms in children are a reason to undergo a comprehensive examination.

Signs of kidney disease:

1. A pink tint to the urine indicates hematuria. This manifestation indicates the possible development of pyelonephritis, urolithiasis or injury to the urinary organs. Colored urine may indicate consumption of beets or grapefruit; such a change is not dangerous.
2. Swelling of the face and limbs may indicate kidney failure.
3. With rare urination and a small amount of fluid (anuria), chronic renal failure is possible.
4. Pale skin is a sign of glomerulonephritis.

Diagnostics

If any of the above symptoms appear, you should undergo a thorough examination, including:

• Ultrasound of the urinary system;
• urography;
• blood and urine tests.

To establish a diagnosis for kidney problems in children, you need to contact a urologist or nephrologist.

Therapy

Treatment depends on the type of disease and is prescribed on an individual basis. Conservative treatment methods are not always effective; in some cases, the problem can only be solved surgically.

Drug therapy for kidney diseases in children includes:

• drugs to lower blood pressure;
• antihistamines;
• diuretics;
• antibiotics.

In the presence of oncological formations, with urolithiasis, as well as with renal failure, surgical intervention is required.

Prevention

To avoid kidney disease in your child, you need to follow some rules. You should start with the diet; spicy, fried, salty foods create additional stress on the baby’s kidneys. It is worth diversifying your diet with calcium-rich dairy products and juices. This will not only improve kidney function, but also strengthen the body's defenses. Children should eat cereals, vegetables and fruits, and pumpkin.

It is very important to keep your lower back and legs warm and avoid hypothermia. At the same time, it is necessary to harden the child’s body and increase resistance to diseases. If there is an infection, follow your doctor's instructions. If a course of antibiotics is prescribed, you need to drink according to the schedule and until the end.

If alarming signs appear, you should immediately seek medical help. Kidney diseases in children cannot be treated on their own; this can lead to serious complications.

Creatinine and urea are the end products of breakdown. Their indicators are used to determine liver disease, kidney disease or study muscle condition. Their indicators are always checked at the same time, as this allows us to determine whether there really has been a failure in the body in the natural elimination of decay products. Let's figure out why creatinine and urea in the blood are elevated.

Clearance (English: clearence) is an indicator of the speed of purification of blood plasma, other media or tissues of the body, i.e. This is the volume of plasma that is completely cleared of a given substance per unit of time:

Renal clearance - clearance characterizing the excretory function of the kidneys, for example, clearance of urea, creatinine, inulin, cystatin C.

Since the kidneys and liver are mainly responsible for the elimination of drugs, an indicator such as clearance can be used to quantify it. So, regardless of the mechanisms by which a particular substance is excreted by the kidneys (filtration, secretion, reabsorption), in general, the renal excretion of this substance can be judged by how much its serum concentration decreases when passing through the kidneys. A quantitative indicator of the degree of removal of a substance from the blood is the extraction coefficient E (for processes subject to first-order kinetics, it is constant):

E = (Ca-Cv) / Ca

where Ca is the serum concentration of the substance in arterial blood,

Cv is the serum concentration of the substance in venous blood.

If the blood, when passing through the kidneys, is completely cleared of this substance, then E = 1.

Renal clearance Cl kidney is equal to:

where Q is the renal plasma flow,

E - extraction coefficient.

For benzylpenicillin, for example, the extraction coefficient is 0.5, and the renal plasma flow is 680 ml/min. This means that the renal clearance of benzylpenicillin is 340 ml/min.

The clearance of substances with a high extraction coefficient (for example, during the elimination of para-aminohippuric acid by the kidneys or propranolol by the liver) is equal to the plasma flow through the corresponding organ. (If a certain substance binds to the formed elements of blood and the bound fraction quickly exchanges with the free fraction (in plasma), then it is more correct to calculate the extraction coefficient and clearance not for plasma, but for whole blood).

The elimination of a substance is best reflected by its total clearance. It is equal to the sum of clearances for all organs where elimination of a given substance occurs. So, if elimination is carried out by the kidneys and liver, then

Сl = Сlпoch + Сlpech

where Cl is the total clearance, Cl kidney is the renal clearance, Cl pech is the hepatic clearance.

Benzylpenicillin, for example, is normally removed by both the kidneys (Clin = 340 ml/min) and the liver (Clin = 36 ml/min). Thus, its total clearance is 376 ml/min. If renal clearance is halved, then the total clearance will be 170 + 36 = 206 ml/min. With anuria, the total clearance becomes equal to the hepatic clearance.

Of course, only that part of the substance that is in the blood is eliminated, and it is this elimination that is reflected by clearance. In order to judge on the basis of clearance the rate of removal of a substance not only from the blood, but also from the body as a whole, it is necessary to correlate clearance with the entire volume in which the substance is located, that is, with Vp (volume of distribution). So, if Vp = 10 l, and Cl = 1 l/min, then 1/10 of the total content of the substance in the body is removed in one minute. This value is called the elimination rate constant k.

Creatinine is a special molecular product that occurs as a result of various chemical processes (metabolism) in human muscles. As a result of chemical reactions - protein metabolism - enormous energy is released into the body, which leads to muscle contraction. This is how creatinine appears. It comes exclusively from the creatine molecule, which is responsible for muscle tone and energy supply.

Once creatinine is created, the body no longer needs it. Therefore, it is excreted into the blood. Then, after moving throughout the body through the circulatory system, creatinine is delivered to the kidneys. The kidneys filter and the creatinine is completely excreted along with the urine. This filtration of the kidneys occurs constantly and without interruption throughout the day. Even when no physical activity is performed, the diet and time of day change. Therefore, creatinine as a by-product does not have time to negatively affect the human body.

Creatinine is necessary for the metabolism of muscle tissue, and it is always present in a small dose in the blood and urine of an absolutely healthy person. It is the level of creatinine in the blood that indicates whether the kidneys are functioning well enough. Only through the kidneys does it leave the body in the same quantity in which it is formed. And when there is a lot of creatinine in the blood, it means the kidneys can’t cope.

There is a special calculation used to determine GFR - glomerular filtration rate (kidney circulation). Glomeruli are microbundles of vessels in nephrons - kidney filters. This calculation is the most accurate analysis, which shows how much blood plasma the kidneys can filter from creatinine and excrete it into urine in 60 seconds. The resulting value is creatinine clearance.

Normal creatinine clearance values

Creatinine clearance is an indicator that is quite different in everyday life for various reasons - the psychological and physical state of the patient’s body, time of day, age and gender of the patient, body weight, improper kidney function.

The normal level of creatinine clearance varies from patient to patient. But there are general ideal norms of indicators:

• Up to 30 years of age for men up to 146 ml per minute, for women up to 134 ml per minute
• up to 40 years of age for a man, ideally 107-139 ml per minute (1.8-2.3 ml per second), for a woman under 40 years old 87-107 ml per minute (1.5-1.8 ml per second )

The creatinine clearance decreases by 1% every year. During the aging process in old age, the normal rate is already 54-105 ml per minute.

When and in what cases are creatinine clearance studies prescribed?

Creatinine clearance measures how fast blood flows through the kidneys. Changes in the norms of indicators when diagnosing creatinine clearance indicate a decrease in renal filtration and, as a result, renal failure, acute or chronic. Analysis of creatinine clearance is prescribed as a test of kidney function in the following situations:

• If renal failure is detected
• during pregnancy
• with pyelonephritis
• with congenital abnormalities of the kidneys
• in the diagnosis of diabetes and other endocrine diseases
• patients after hemodialysis
• for assessing muscle loads in athletes, astronauts
• in experimental medicine

Definition, creatinine clearance formula.

To determine the functioning of the kidneys, there are 3 main ways to determine creatinine clearance:

1. Analysis of urine collected by the patient over a 24-hour period
2. Blood test using a calculation formula. This diagnosis is carried out most often, being the most convenient for the patient.
3. Rehberg's test

Analysis of urine. When diagnosing the level of creatinine clearance in this way, the patient collects his urine in a certain volume in a clean container within 24 hours, refusing the day before and within exactly 24 hours from the time of the first collection of urine from caffeine and tea, beets and products with unnatural dyes. The container with collected urine should be kept either cool and dark or in the refrigerator. A urine test determines the ability of the kidneys to eliminate substances harmful to the body.

Blood analysis. There is a special formula for calculating creatinine clearance. The main parameters are the age and weight of the patient and, necessarily, the level of creatinine in the venous blood. The formula is: (140-age)*(body weight in kg)/(72*creatinine level in mg/dL). When calculating, a female patient needs to multiply the result obtained from the formula by the index 0.85

2 days before blood sampling, any physical activity is prohibited so as not to increase the daily normal creatinine level in the muscles. The day before the test, avoid meat, legumes, baked goods and fatty foods. You need to drink up to 2 liters per day. You should not eat in the morning before the test. Especially in this method, you need to pay attention to the children's formula, which differs from the formula for adults, because age is one of the main indicators in the calculation: child’s body length in cm/(0.0113 * creatinine level in the blood, µmol/l)*K . The “K” indicator in this formula is the coefficient of the age of the child patient. For children 2-14 years old and girls over 14 - the coefficient is 0.55, for boys over 14 - 0.7, for a full-term child under 2 years old - a coefficient of 0.45, for premature babies - a coefficient of 0.33.

When the clearance of endogenous (muscle) creatinine falls below the norm indicated in the previous chapter, this is an indicator of chronic kidney disease. At a level of less than 60 ml per minute, the kidneys are considered damaged, and at a level below 20 ml per minute, a severe form of renal failure is accurately established.

Reberg-Tareev test. This method is also called endogenous creatinine clearance, glomerular filtration rate (GFR) and is considered more accurate. Collecting urine and taking a blood test at the same time. Before taking the test, you need to drink 0.5 liters of water, preferably in the morning on an empty stomach. The first urine is passed, it is collected during the second urination, when a blood test is taken at the same time. This test diagnoses many kidney disease problems. Normally, according to the calculation of the Reberg-Tareev test, the indicator is 65-125 ml per minute.

If the GFR result is underestimated, renal failure is detected. GFR with a result of 30-59 indicates chronic renal failure. A result below 30 means the kidneys are not functioning properly; dialysis is prescribed urgently.

Norm and tests for the presence of creatinine in the blood

The blood creatinine level is a constant value and is measured in micromoles/liter. In order not to lose control of the proper filtration functioning of the kidneys, it is important to monitor the creatinine level using tests and kidney samples.

Prescribing a test for the presence of creatinine in the blood in cases where:

• assessment of kidney function is necessary in cases of detected chronic renal failure
• hemodialysis is prescribed with a critical level of creatinine in the blood
• urolithiasis is suspected
• the subject decided to become a kidney donor

When preparing for the test, 2 days before donating blood, avoid increased physical activity, do not drink coffee, tea, alcohol for 24 hours, do not eat meat and protein products, do not eat half a day before the test, drink only still water.

The main source of creatinine production is human muscles. Men's muscles are very different from women's. Therefore, normal levels of creatinine in the blood of men and women have different values; in men this figure is naturally higher. Also, in addition to muscle mass, nutrition and how active your lifestyle are are also important. Athletes and gym goers may have significantly higher creatinine levels due to the increased consumption of amino acids in the body. Those on a protein diet and meat eaters may also have elevated creatinine levels. The age and pregnancy of the patient also matters.

Normal blood creatinine level:

• in an adult male 70-110 mmol/min
• in an adult woman 50-93 mmol/min
• in newborns and children under one year of age 18-35 mmol/min
• in adolescents under 15 years of age 27-75 mmol/min

Increased creatinine in blood tests. Causes.

Sometimes the creatinine level in the blood changes slightly or greatly. This happens for various reasons:

1. When creatinine does not leave the body due to kidney damage (urolithiasis, renal failure, pyelonephritis, glomerulonephritis, uremia), decreased blood supply to the kidneys, severe shock.
2. When there is an increased level of creatinine in the blood. There are a lot of factors here - endocrine diseases (diabetes mellitus), frequent irradiation of the body, excessive physical activity (weightlifting, bodybuilding, improper diet (large amount of protein consumption), abuse of sports nutrition, with an increased content of growth hormone in the body (gigantism), severe skin injuries and operations, destruction of muscle tissue (compression) due to car accidents, various infectious diseases, loss of large amounts of blood, internal ulcers and tumors, anemia.

Symptoms of elevated creatinine are fatigue, fatigue, difficulty breathing, a feeling of exhaustion, and confusion.

Treatment for increased creatinine depends on the degree of the indicator. If this does not particularly affect the general condition of the body and the indicator is within the acceptable norm, doctors recommend a special diet, reduced physical activity, increased consumption of clean drinking water, diuretics, antioxidants to remove waste and toxins, and normalization of sleep. If the indicator deviates significantly from the norm, you need to contact a specialist who will select the right treatment.

Decreased creatinine in blood tests and its causes

A low creatinine level is also a pathology and has a negative effect on the body. The reasons for it are as follows: low muscle mass, severe muscle injuries, a diet with low protein intake, cirrhosis of the liver, pregnancy, amputation of limbs, long-term treatment with allergy medications, a vegetarian diet, blockage of the urinary tract.

In this case, you cannot independently prepare a diet based on diets and hunger strikes, and reduce sports activities to a minimum. Taking medications under the supervision of a doctor.

An increase, as well as a decrease, in the level of creatinine in the blood has quite serious consequences if you do not pay attention. Therefore, try to check with your doctor during blood tests to see if there are any abnormalities.