Proteinuria. Clinical significance of detecting total protein in urine

Proteinuria is the excretion of protein in the urine in quantities exceeding normal values. This is the most common sign of kidney damage. Normally, no more than 50 mg of protein, consisting of filtered plasma low-molecular proteins, is excreted into the urine per day.

• Defeat renal tubules(interstitial nephritis, tubulopathies) leads to impaired reabsorption of filtered protein and its appearance in the urine.
• Hemodynamic factors - the speed and volume of capillary blood flow, the balance of hydrostatic and oncotic pressure are also important for the appearance of proteinuria. The permeability of the capillary wall increases, contributing to proteinuria, both with a decrease in the speed of blood flow in the capillaries, and with glomerular hyperperfusion and intraglomerular hypertension. The possible role of hemodynamic changes should be taken into account when assessing proteinuria, especially transient proteinuria, and in patients with circulatory failure.

Symptoms and diagnosis of proteinuria

In connection with diseases Proteinuria is divided into functional and pathological.

Functional proteinuria observed in patients with healthy kidneys. Functional proteinuria is low (up to 1 g/day), usually transient, isolated (there are no other signs of kidney damage), rarely combined with erythrocyturia, leukocyturia, cylindruria. There are several types of functional proteinuria:

• Orthostatic. Occurs in young people 13-20 years old, does not exceed 1 g/day, disappears in the supine position. This type proteinuria is diagnosed using orthostatic test- the patient collects the first morning portion of urine without getting out of bed, then performs a small physical activity (walking up the stairs), after which he collects the second portion of urine for analysis. The absence of protein in the first portion and the presence of urine in the second portion indicate orthostatic proteinuria.
• Feverish (up to 1-2 g/day). It is observed during febrile conditions, more often in children and the elderly, disappears when body temperature normalizes, it is based on an increase in glomerular filtration.
• Tension proteinuria (marching). It occurs after severe physical stress, is detected in the first portion of urine, and disappears with normal physical activity. It is based on the redistribution of blood flow with relative ischemia of the proximal tubules.
• Proteinuria in obesity. Associated with the development of intraglomerular hypertension and hyperfiltration against the background of increased concentrations of renin and angiotensin. For weight loss and treatment ACE inhibitors may decrease and even disappear.
• Physiological proteinuria. Pregnancy can lead to its appearance, since it is accompanied by an increase in glomerular filtration without an increase in tubular reabsorption. The level should not exceed 0.3 g/day.
• Idiopathic transient. Is detected in healthy individuals during medical examination and is absent during subsequent urine tests.

Pathological proteinuria detected in kidney diseases, urinary tract, as well as when exposed to extrarenal factors.

By source Proteinuria can be prerenal, renal and postrenal.

Prerenal, or proteinuria "overflow", observed in multiple myeloma (Bence Jones proteinuria), rhabdomyolysis, Waldenström macroglobulinemia, massive intravascular hemolysis. Overflow proteinuria can range from 0.1 to 20 g/day. High proteinuria (more than 3.5 g/day) in this case is not a sign of nephrotic syndrome, since it is not accompanied by hypoalbuminemia and its other signs. To identify myeloma nephropathy, the patient needs to have his urine tested for Bence Jones protein.

Renal proteinuria According to the mechanism of occurrence, it can be glomerular and tubular.

Glomerular proteinuria is observed in most kidney diseases - glomerulonephritis (primary and with systemic diseases), renal amyloidosis, diabetic glomerulosclerosis, as well as hypertension, “stagnant” kidney.

Tubular proteinuria is observed with interstitial nephritis, pyelonephritis, congenital tubulopathies (Fanconi syndrome) and other kidney diseases with predominant damage to the tubules.

Glomerular and tubular proteinuria are differentiated by the presence of α1-microglobulin and a quantitative comparison of the level of albumin and β2-microglobulin in the urine, which normally ranges from 50:1 to 200:1. An albumin to β2-microglobulin ratio of 10:1 and α1-microglobulin indicate tubular proteinuria. With glomerular proteinuria, this ratio will exceed 1000:1.

Postrenal proteinuria has extrarenal origin, develops in the presence of bacterial inflammatory process in the urinary system (pyelonephritis) due to increased exudation of plasma proteins into the urine.

By composition There are selective and non-selective proteinuria.

Selective proteinuria characterized by the release of protein with low molecular weight, mainly albumin. Prognostically, it is considered more favorable than non-selective.

At non-selective proteinuria protein is released with medium and high molecular weight (α2-macroglobulins, β-lipoproteins, γ-globulins). A wide protein spectrum of non-selective proteinuria indicates severe defeat kidneys, characteristic of postrenal proteinuria.

By severity (magnitude) They distinguish microalbuminuria, low, moderate, high (nephrotic) proteinuria.

Microalbuminuria- excretion in urine of minimal albumin, only slightly exceeding the physiological norm (from 30 to 300-500 mg/day). Microalbuminuria is the first early symptom of diabetic nephropathy, kidney damage caused by arterial hypertension, kidney transplant rejection. Therefore, categories of patients with such indicators should be prescribed a 24-hour urine test for microalbuminuria in the absence of changes in the general urine test.

Low(up to 1 g/day) and moderate(from 1 to 3 g/day) are observed in various diseases of the kidneys and urinary tract (glomerulonephritis, pyelonephritis, nephrolithiasis, kidney tumors, tuberculosis, etc.). The amount of proteinuria depends on the degree of kidney damage and the severity of the inflammatory process in the urinary tract.

At high (nephrotic) proteinuria protein loss is more than 3.5 g/day. The presence of high proteinuria combined with hypoalbuminemia is a sign of nephrotic syndrome.

It should be remembered that the protein concentration in single portions of urine varies throughout the day. For a more accurate idea of ​​the severity of proteinuria, daily urine is examined (daily proteinuria).

It is difficult to determine daily proteinuria at home; you will need to take at least a test. Based on its results, one can not only judge the presence or absence of a symptom, but also make assumptions regarding concomitant pathologies, as well as determine a set of diagnostic and therapeutic measures. However, maybe functional phenomenon and do not require treatment.

The formation of proteinuria in the human body

In the process of performing its main task, a small amount of protein is filtered from the bloodstream. This is how it appears in primary urine.

Next, the mechanism of protein reabsorption in the renal tubules is triggered. The result of the functioning of healthy kidneys and the absence of excess proteins in the blood plasma is the presence of a small amount of protein in secondary urine (the fluid that is excreted from the body).

A laboratory test of urine does not detect proteins at this concentration, or gives a result of 0.033 g/l.

Exceeding this value is called proteinuria - the content of protein in urine in large quantities. This condition is a reason for further diagnosis in order to identify the causes of the disorder.

Types of proteinuria - physiological and pathological forms

Depending on the source of protein in urine, one can distinguish following types violations:

1. Renal(renal) - in which excess protein is formed due to defects in glomerular filtration (glomerular or glomerular proteinuria), or when reabsorption in the tubules is impaired (tubular or tubular).
2. Prerenal– occurs when there is an inadequately high formation of protein compounds in the blood plasma. Healthy kidney tubules are not able to absorb such amounts of protein. May also occur when artificial introduction albumin on the background.
3. Postrenal– caused by inflammation of the lower organs genitourinary system. The protein enters the urine that comes out of the kidney filter (hence the name - literally “after the kidneys”).
4. Secretory– characterized by the release of a number of specific proteins and antigens against the background of certain diseases.

All of the listed mechanisms of protein getting into the urine are characteristic of a pathological process in the body, therefore such proteinuria is called pathological.

Functional proteinuria is most often an episodic phenomenon, not accompanied by diseases of the kidneys or genitourinary system. These include the following forms of violation:

1. Orthostatic(lordotic, postural) - the appearance of protein in the urine in children, adolescents or young people of asthenic physique (often against the background lumbar lordosis) after a long walk or being in a static vertical position.
2. Nutritional– after eating protein foods.
3. Proteinuria tension(working, marching) – occurs under conditions of extensive physical activity (for example, among athletes or military personnel).
4. Feverish– occurs as a result of increased decay processes in the body or damage to the kidney filter when body temperature rises above 38 degrees.
5. Palpation– may appear against the background of prolonged and intense palpation of the abdominal area.
6. Emotional– diagnosed during severe stress or acts as its consequence. This can include the transient form, also associated with shock changes in the body due to hypothermia or heat stroke.
7. Stagnant– a phenomenon accompanying abnormally slow blood flow in the kidneys or oxygen starvation body in case of heart failure.
8. Centrogenic– occurs with concussions or epilepsy.

The appearance of proteins in the urine in functional forms can be explained by mechanisms similar to pathological forms. The only difference is the transitory nature and quantitative indicators.

It is worth noting that the last two functional forms are often combined under the name of extrarenal proteinuria, which is also included in the list of pathological forms.

Norms of daily proteinuria

Based on the abundance of only the main types of functional forms, it can be assumed that a one-time excess of the amount of protein in the urine is not always necessary and is clearly not sufficient to identify a stable trend. Therefore, it is more correct to use the results of the analysis.

If there is a row physiological reasons daily norm may also be exceeded by healthy people, to make a diagnosis, it is necessary to take into account the patient’s complaints, as well as other quantitative indicators of urine analysis (red blood cells,).

General norm daily protein for adults – 0.15 g/day, and according to other reference data – 0.2 g/day (200 mg/day) or a lower value – 0.1 g/day.

These figures, however, are only valid for 10-15% of the population; the vast majority excrete only 40-50 mg of protein in urine.

During pregnancy, the volume of blood flow in the kidneys increases, and the amount of filtered blood increases accordingly. This is taken into account when calculating protein norms. Non-pathological indicator in pregnant women is less than 0.3 g/day (150-300 mg/day).

Norms for children can be presented in table form:

Some deviation from the norm (increasingly) can be observed in children in the first week of life.

For any type of functional proteinuria quantitative indicator rarely exceeds 2 g/day, and more often – 1 g/day. Similar values ​​can be observed in some pathologies; here it is important to carry out additional research and examination of the patient. The exception is pregnant women, whose daily value is more than 0.3 g/day, which already makes it possible to suspect the presence of pregnancy complications with a high probability.

Causes of protein in urine

It is convenient to consider the general list of diseases, a sign of which is the presence of protein in the urine, in accordance with the pathological forms. The prerenal form of proteinuria can occur against the background of:

• some types of systemic and regional hemoblastoses - malignant changes in hematopoietic and lymphatic tissue (including multiple myeloma);
• diseases connective tissue– disorders of an allergic nature, in which various (from 2) body systems are affected;
• rhabdomyolysis - a condition characterized by destruction muscle tissue And sharp increase blood concentrations of myoglobin protein;
• macroglobulinemia - a disease in which malignantly modified plasma cells begin to secrete a viscous protein - macroglobulin;
• hemolytic anemia – accompanied by the breakdown of red blood cells and the release of a large amount of hemoglobin protein into the blood (may occur due to poisoning with specific poisons);
• transfusion of incompatible blood or taking medications (sulfonamides);
• the presence in the body of metastases or tumors localized in the abdominal cavity;
• poisoning;
• epileptic seizure or traumatic brain injury, including those accompanied by cerebral hemorrhage.

The causes of the renal form are directly renal pathologies:

• – characterized by damage to the glomerular apparatus of the kidneys, and in some cases, death of tubular tissue;
• – impaired renal function that occurs against the background of changes in the metabolism of fats and carbohydrates with high blood pressure;
• hypertensive – “wrinkling” of the kidney tissue as a result of vascular damage due to high blood pressure;
• renal neoplasms;
• – deposition of protein complexes – amyloids – in the kidneys;
• inflammatory kidney diseases, in particular interstitial nephritis - inflammation of the connective tissue of the tubules.

Postrenal proteinuria may be a symptom of:

• inflammatory diseases of the lower genitourinary system – Bladder, urethra, genitals;
• bleeding from the urethra;
• benign neoplasms of the bladder () and urinary tract.

In all of these (postrenal) cases, the epithelial cells of the mucous membrane are damaged. Their destruction releases proteins, which are found in urine.

Proteinuria in children can also develop due to a number of the listed reasons. In this case, the occurrence of excess protein against the background of:

• hemolytic disease of newborns is a type of hemoblastosis, the specificity of which is the incompatibility of the blood of the mother and the fetus. Pathology can begin to develop even in the intrauterine period of the embryo’s life;
• fasting or eating disorder;
• excess vitamin D;
• allergies.

An increase in the amount of protein in urine during pregnancy may also have a number of additional reasons:

• nephropathy of pregnancy;
• toxicosis (in the first trimester) – violation water-salt balance against the background of dehydration, leading to changes in overall metabolism;
• gestosis (preeclampsia) is a complicated pregnancy, accompanied by hypertension, cramps, edema, proteinuria. The condition is usually diagnosed in the 2nd and 3rd trimester.

Symptoms accompanying this disease

Common signs that urinary protein loss is occurring include:

• edematous manifestations, in particular morning swelling century;
• the appearance of whitish foam or dirty white flakes on the surface of urine.

Differentiated signs may include both symptoms of loss of a certain type of protein compounds, and symptoms of the underlying cause of proteinuria. Among the first:

• general decrease in immunity;
• anemic manifestations;
• tendency to bleed;
• weakness, decreased muscle tone;
• hypothyroidism

The second includes mainly signs indicating the presence of renal pathologies:

• pain in the kidneys, including;
• discomfort when urinating;
• increased blood pressure;
• high fever, chills, muscle pain;
• weakness, dry skin;
• change in the color, consistency or smell of urine;
• diuresis disorders.

However, the main source of information for making a diagnosis and determining the cause of excess protein is laboratory tests.

Method of diagnosing the disease

After a one-time detection of proteinuria as a result general analysis urine should be differentiated between functional and pathological form. This may require:

• collecting patient complaints, determining the presence of factors that can provoke an episodic increase in protein levels;
• orthostatic test - performed in children and adolescents.

If there is a suspicion of concomitant pathology, then they are assigned:

• daily protein analysis;
• tests for specific proteins (Bence-Jones);
• examination by a urologist or gynecologist;
• , genital organs (if indicated).

• general and biochemical blood tests.

Naturally, the complex of additional examinations can expand significantly, according to the fact that proteinuria can be caused by the most various diseases, acting as a primary/secondary cause of increased protein levels.

How to prepare for the test

No special measures are required, but some nuances are worth considering:

• You must notify your doctor about taking any medications on an ongoing basis and, if necessary, agree with him on the advisability of their use on the day of the test;
• do not change drinking regime, both before and during it;
• do not eat unusual foods, follow your usual diet;
• exclude alcoholic drinks;
• the day before the test, you should stop taking vitamin C;
• avoid physical and nervous overload;
• If possible, provide the body with adequate sleep.

How to take a daily protein test correctly

To obtain an adequate analysis result, the patient will need to follow the following algorithm:

1. Prepare (purchase) in advance for collecting the daily volume of urine.
2. There is no need to collect the first portion of morning urine.
3. Now, with each urination, urine should be added to the container, recording the time of each diuresis. Store the collected volume only in the refrigerator.
4. You need to collect all urine, including the first morning portion the day after the start of collection (to get urine output for the day).
5. After completing the collection, record the resulting volume of liquid;
6. Mix the urine and pour from 30 to 200 ml into a separate sterile container.
7. Submit the container to the laboratory, adding a recorded graph of diuresis, as well as indicating the final volume of fluid received, your height and weight.

Minor proteinuria can be corrected at home using the following measures:

• minimizing physical and emotional stress;
• making changes to your diet - consume less heavy proteins (fatty meat and fish, mushrooms, legumes) and salt, while increasing the amount of fiber - steamed vegetables, fruits, cereals, bread and fermented milk products, milk and vegetable soups.

Diet for increased content Protein also involves avoiding alcoholic beverages and cooking food with a small amount of fat - boiling or steaming.

There are many known folk remedies that help reduce the amount of protein in the urine, here are some of them:

• infusions of seeds or roots of parsley, birch buds, bearberry;
• (grains, not flakes), corn grains or fir bark;
• decoction of pumpkin seeds instead of tea;
• teas and;
• infusions of linden and lemon zest.

Recipes for decoctions of herbs, tree bark and grains for drinking:

1. Brew a teaspoon of chopped parsley seeds with boiling water and leave for several hours. Take several sips throughout the day.
2. Pour boiling water over two tablespoons of birch buds and leave for 1-2 hours. Take 50 ml 3 times a day.
3. Boil 4 tablespoons of corn kernels in water (about 0.5 liters) until softened. Then strain and drink throughout the day. The decoction should not be stored for longer than a day.
4. Boil 5 tablespoons of oat grains in a liter of water until softened; take the decoction in the same way as corn decoction.

During pregnancy, the diet does not lose its relevance, as does the use of folk remedies. But taking chemical medications should be strictly as prescribed by the doctor (although this recommendation should not be neglected even in the absence of pregnancy).

It is important to understand that at home you can only fight a functional disorder or one that is just beginning to develop. In case of massive deviations from the norm as a result of urine analysis and severe symptoms, the listed measures can act as an addition to the main drug therapy.

But the latter can be represented by drugs of various groups:

• latest generation statins - for treatment diabetes mellitus and vascular atherosclerosis (some statins, however, may themselves promote proteinuria);
• ACE inhibitors and angiotensin blockers - used for heart pathologies, in particular arterial hypertension;
• calcium channel blockers - often used to treat the combination of hypertension and diabetes mellitus;
• antitumor drugs – used in the presence of benign or malignant neoplasms;
• antibiotics and – are prescribed in the presence of an inflammatory process and/or the presence of infections;
• anticoagulants – have a complex effect in acute glomerulonephritis and renal failure;
• non-hormonal immunosuppressants (cytostatics) – suppress inflammatory autoimmune process with glomerulonephritis or nephrotic syndrome due to high blood pressure;
• complex or narrowly targeted means to reduce swelling;
• hormonal drugs (corticosteroids) - have anti-allergic and anti-inflammatory effects, but can increase blood pressure.

Treatment of severe proteinuria, also complicated serious illness, may require effort and significant time investment. Therefore, even with the occasional appearance of protein in the urine, one should not neglect the diagnosis and use of “homemade” therapeutic measures in order to prevent the development of pathologies of the kidneys and the body as a whole.

Proteinuria is a condition in which an amount of protein that is significantly higher than normal is excreted in urine. This is not independent nosological unit– this is a peculiar symptom, which in most clinical situations indicates the progression of kidney pathologies. Normally, up to 50 mg of protein is excreted in urine in one day.

It is impossible to detect proteinuria on your own. An increased concentration of this substance in urine can only be detected through laboratory tests. It is worth noting that this state It can occur equally in both adults and children. Proteinuria during pregnancy is also possible.

Etiology

The reasons for the progression of proteinuria in patients are quite varied. But it is worth noting the fact that they are the same in both adults and children. As a rule, the main cause of proteinuria is pathologies of the kidneys and the urinary system as a whole.

Proteinuria progresses against the background of such ailments:

• - one of the most common reasons proteinuria;
• myeloma;
• tubular proteinuria;
• renal vessels;
• glomerular proteinuria;
• acute tubular necrosis;
• diabetic glomerulosclerosis;
• potassium kidney;
• congestive kidney;
• myoglobinuria;
• hemoglobinuria.

Proteinuria can also be caused by. Often it appears in the background. The reasons for increased protein concentration in urine in children and adults include the presence of a malignant lesion is vital important organs(heart, brain, lungs, etc.).

Varieties

Depending on the connection with pathologies:

• functional proteinuria;
• pathological

Depending on the source:

• postrenal;
• renal It is divided into tubular and glomerular;
• prerenal or congested.

Depending on the composition:

• selective proteinuria;
• non-selective.

Depending on the severity:

• microalbuminuria;
• low;
• moderate;
• high.

Functional proteinuria can occur in patients with completely healthy kidneys. If it develops, the protein concentration in urine increases above normal by 50 mg (in total, 1 gram of protein is excreted in the urine per day). In this case, the increase in protein is isolated or transient in nature and is rarely combined with cylindruria, erythrocyturia, and leukocyturia.

Types of functional proteinuria:

• orthostatic proteinuria. It is most often detected in people aged 13 to 20 years. It is rarely diagnosed in children. With orthostatic proteinuria, an increase in protein concentration in urine up to 1 gram per day is observed. What's remarkable is this symptom disappears when lying down;
• febrile. An increase in protein above normal is observed during feverish conditions. This is usually observed in children and the elderly. As soon as the body temperature drops to normal indicators, the level of protein in the urine also returns to normal;
• tense. It occurs rarely in children. It usually appears during increased physical activity and disappears as soon as the load returns to normal;
• increase in protein with;
• physiological. Usually observed in women during pregnancy;
• idiopathic transient.

Symptoms

Proteinuria in itself is a symptom of some pathological conditions in children and adults. Its presence can be detected through laboratory diagnostics. It is quite difficult to independently determine whether you have this condition, since the symptoms are scarce.

The following symptoms may indicate the development of proteinuria:

• swelling of the eyelids (especially in morning time). This sign more often observed in children;
• a specific whitish “foam” appears in the urine;
• in urine you can notice sediment or “flakes” that have a white or grayish color.

If you notice such signs in yourself, you should immediately go to medical institution for an appointment with a nephrologist or urologist for complex diagnostics. It is important to remember that proteinuria is not a disease, but a sign indicating that some pathology is developing in the human body.

Diagnostics

During diagnostics, it is important not only to identify increased concentration protein in urine, but also to identify the real reason this. The doctor will need to clarify which one Standard plan diagnostics:

• inspection;
• history taking and symptom assessment;
• Rehberg's test;
• urine analysis according to Nechiporenko;
• bacterial culture of urine;
• and urinary tract;
• daily proteinuria.

Therapeutic measures

Treatment will be prescribed only after the doctor identifies the true cause of the increase in protein concentration in urine. After all, it is not proteinuria that needs to be treated, but the illness that provoked it. Therefore, the patient’s treatment plan includes the following pharmaceuticals:

• anticoagulants;
• antibiotics. They are added to the treatment plan if an infectious focus is detected;
• antihypertensive drugs are used to correct blood pressure;
• preparations containing active substances, reducing swelling;
• anti-inflammatory drugs;
• antitumor drugs are used to treat tumor processes benign and malignant.

The treatment plan also necessarily includes diet therapy. It is based on the following principles:

• The diet must include pumpkin, steamed vegetables, beets, and fruits;
• should be excluded from daily ration foods containing protein;
• reduce the amount of salt consumed;
• consume more milk and dairy products.

Pathology treatment is carried out in inpatient conditions, to medical specialists could monitor the patient's condition. If necessary, the treatment plan can be adjusted. Many patients prefer the means traditional medicine, because they consider them more natural and safe. But it is worth remembering that for the treatment of any ailment, they can be taken only after agreement with your doctor. Self-medication is unacceptable.

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Normally, in the urine of healthy people, protein is present in minimal quantities - in the form of traces (no more than 0.033 g/l), which cannot be detected using qualitative methods. More high content protein in the urine is assessed as proteinuria.

Proteinuria is the appearance of protein in the urine in quantities at which qualitative reactions to protein become positive.

Depending on the protein content in the urine, there are:

• mild proteinuria - up to 1 g/l;
• moderate proteinuria - 2-4 g/l;
• significant proteinuria - more than 4 g/l.

Proteinuria occurs when protein filters from the blood into the kidneys or protein attaches to urine in the urinary tract. Depending on the reason there are the following types proteinuria:

1. Renal (renal):

• functional;
• organic.

1. Extrarenal (extrarenal).

Renal (renal) proteinuria occurs as a result of increased permeability of the renal filter due to damage (organic) and without damage (functional) to the kidneys.

Functional proteinuria occurs due to an increase in the permeability of the renal filter in response to strong external irritation or a slowdown in the passage of blood in the glomeruli.

Among them are:

1. Physiological proteinuria in newborns happens quite often in the first 4-10 days after birth and is caused by the presence of a functionally fragile renal filter in the newborn, as well as, probably, by birth trauma;
2. Alimentary proteinuria - occurs after eating protein foods (egg whites);
3. Orthostatic proteinuria - more often observed in adolescents, emaciated people, asthenics with lordosis of the lower thoracic spine. Protein in the urine can appear in significant quantities during prolonged standing, severe curvature of the spine (lordosis), and also in the case of sudden change body position from lying to standing;
4. Feverish proteinuria - occurs when elevated temperature body up to 39-40 °C at infectious diseases. The causative agent of the infection and the increased temperature irritate the renal filter, leading to an increase in its permeability;
5. Proteinuria caused by nervous (emotional) and physical (marching) overloads of the body;
6. Proteinuria in pregnant women;
7. Congestive proteinuria - observed in patients with cardiac vascular diseases, with ascites, abdominal tumors (up to 10 g/l). When blood movement slows down in the vascular glomeruli of the nephron, glomerular hypoxia develops, which leads to an increase in the permeability of the renal filter. Prolonged stagnation of blood can cause organic kidney damage and lead to organic proteinuria.

So, the cause of functional renal proteinuria is an increase in the permeability of the renal filter (in particular the wall of the glomerular vessels); damage to the renal filter does not occur. Therefore, functional proteinuria is usually: mild (up to 1 g/l); are represented by low molecular weight proteins (albumin), short-term (disappear after the end of the stimulus on the renal filter).

Organic proteinuria occurs due to increased permeability of the renal filter as a result of damage to the renal parenchyma. This type of renal proteinuria is observed in acute and chronic nephritis, nephrosis, nephrosclerosis, infectious and toxic lesions kidneys, as well as in persons with congenital anatomical abnormalities of the kidneys, for example, in the case of polycystic disease, when anatomical changes cause significant organic damage to the renal tissue.

The severity of proteinuria does not always indicate the severity of damage to the renal parenchyma. Sometimes acute glomerulonephritis with high proteinuria can quickly end in recovery, and chronic glomerulonephritis with low protein content in the urine can last a long time and even cause death. Reducing proteinuria in cases of acute glomerulonephritis is mainly good sign, and in chronic forms, such a decrease is very often accompanied by a deterioration in the patient’s condition, as it may be due to functional kidney failure with a decrease in their filtration capacity, due to the death of a large number of renal glomeruli. Moderate proteinuria is recorded in acute and chronic glomerulonephritis, systemic lupus erythematosus, and renal amyloidosis. Significant proteinuria is characteristic of nephrotic syndrome.

Acute and chronic glomerulonephritis. Proteinuria occurs as a result of damage to the renal filter. In glomerulonephritis, antibodies attack the renal filter, resulting in an increase in its filtration capacity, but since tubular reabsorption is not impaired, most of the filtered protein is reabsorbed into the blood as urine passes through the tubular system. Thus, with glomerulonephritis, proteinuria is a constant phenomenon, its level is moderate (up to 5 g/l).

Nephrotic syndrome. Proteinuria occurs due to impaired tubular reabsorption of filtered protein as a result of damage to the renal tubules. Therefore, in nephrotic syndrome, proteinuria is a constant phenomenon, the level of proteinuria is significant (10-30 g/l). It is represented by albumins and globulins.

So, the pathogenesis of organic renal proteinuria is based on an increase in the permeability of the renal filter due to organic damage kidney parenchyma. Therefore, organic proteinuria is usually moderate or pronounced; long-term; combine with others pathological changes in the urine (hematuria, cylindruria, disfoliation of the renal tubular epithelium).

Extrarenal (extrarenal) proteinuria is caused by protein impurities (inflammatory exudate, destroyed cells), which is released through the urinary tract and genitals. Occurs in cystitis, urethritis, prostatitis, vulvovaginitis, urolithiasis and tumors urinary tract. The amount of protein in extrarenal proteinuria is insignificant (up to 1 g/l).

Extrarenal proteinuria is usually combined with other pathological changes in the urine (leukocyturia or pyuria and bacteriuria).

IN Lately In the domestic literature, the question is often discussed: what is considered proteinuria? If earlier proteinuria was simply called the detection of protein in urine using conventional qualitative or quantitative methods, the sensitivity and specificity of which were not very high, now, given the increasing introduction into practice of more sensitive and specific methods, proteinuria is said to be when the level of protein in the urine exceeds the norm . The concept of normal protein in urine also varies - which is due to the use of both old and new methods for determining protein in urine, which differ in sensitivity and specificity. Some authors, taking into account the presence of protein in the urine of a healthy person, understand the term proteinuria as generally the excretion of protein in the urine and, for simplicity, divide proteinuria into physiological and pathological, which is now also being debated. Usually under the term proteinuria refers to an increase in protein content in the urine.

In most laboratories, when testing urine “for protein,” they first use qualitative reactions that do not detect protein in the urine of a healthy person. If protein in the urine is detected by qualitative reactions, its quantitative (or semi-quantitative) determination is carried out. In this case, the features of the methods used, covering a different spectrum of uroproteins, are important. Thus, when determining protein using 3% sulfosalicylic acid, the amount of protein up to 0.03 g/l is considered normal, but when using the pyrogallol method, the limit of normal protein values ​​increases to 0.1 g/l. In this regard, the analysis form must indicate the normal protein value for the method used by the laboratory.

When determining the minimum amounts of protein, it is recommended to repeat the analysis; in doubtful cases, the daily loss of protein in urine should be determined. Normally, daily urine contains protein in small quantities. Under physiological conditions, the filtered protein is almost completely reabsorbed by the epithelium of the proximal tubules and its content in the daily amount of urine varies, according to different authors, from traces to 20 - 50, 80 - 100 mg and even up to 150 - 200 mg. Some authors believe that daily protein excretion in the amount of 30–50 mg/day is physiological norm for an adult. Others believe that urinary protein excretion should not exceed 60 mg/m2 of body surface per day, excluding the first month of life, when the amount of physiological proteinuria can be four times higher than the indicated values.

General condition The appearance of proteins in the urine of a healthy person is their fairly high concentration in the blood and molecular weight of no more than 100 - 200 kDa.

In practically healthy people, under the influence of various factors, transient proteinuria. This proteinuria is also called physiological, functional or benign, since it, unlike pathological, does not require treatment.

Physiological proteinuria

March proteinuria

Transient protein excretion in the urine in healthy people may appear after severe physical activity(long hikes, marathon running, game types sports). This is the so-called working (marching) proteinuria or tension proteinuria, observed and described by many researchers. The works of these authors, illustrating the possibility of the development of proteinuria under the influence of physical activity, indicate high degree its severity, as well as its reversibility. The genesis of such proteinuria is explained by hemolysis with hemoglobinuria and stress secretion of catecholamines with a transient disturbance of glomerular blood flow. In this case, proteinuria is detected in the first portion of urine after physical activity.

The importance of the cooling factor in the genesis of transient proteinuria was noted in healthy people under the influence of cold baths.

Albuminuria solaris

Known albuminuria solaris, which occurs when there is a pronounced reaction of the skin to insolation, as well as when the skin is irritated by certain substances, for example, when it is lubricated with iodine.

Proteinuria with increased levels of adrenaline and norepinephrine in the blood

The possibility of the appearance of proteinuria with an increase in the level of adrenaline and norepinephrine in the blood has been established, which explains the release of protein in the urine during pheochromocytoma and hypertensive crises.

Nutritional proteinuria

Highlight nutritional proteinuria, sometimes appearing after eating a large protein meal.

Centrogenic proteinuria

The possibility of occurrence has been proven centrogenic proteinuria– for epilepsy, concussion.

Emotional proteinuria

Described emotional proteinuria during exams.

Palpable proteinuria

Proteinuria of functional origin also includes the release of protein in the urine, described by some authors, during vigorous and prolonged palpation of the abdomen and kidney area ( palpable proteinuria).

Feverish proteinuria

Feverish proteinuria observed in acute febrile conditions, more often in children and the elderly. Its mechanism is poorly understood. This type of proteinuria persists during the period of increased body temperature and disappears when it decreases and normalizes. If proteinuria persists for many days or weeks after body temperature has returned to normal, the possibility of organic disease kidney - either newly emerged or already existing.

Congestive (cardiac) proteinuria

In heart disease, it is often detected stagnant, or cardiac proteinuria. As the heart failure resolves, it usually goes away.

Proteinuria of newborns

In newborns, physiological proteinuria is also observed in the first weeks of life.

Orthostatic (postural, lordotic) proteinuria

Orthostatic (postural, lordotic) proteinuria observed in 12–40% of children and adolescents, characterized by the detection of protein in the urine during prolonged standing or walking with rapid disappearance (transient variant of orthostatic proteinuria) or its decrease (persistent variant) in horizontal position. Its genesis is associated with disturbances of renal hemodynamics, developing due to lordosis, compressing the inferior vena cava in a standing position, or the release of renin (angiotensin II) in response to changes in the volume of circulating plasma during orthostasis.

Physiological proteinuria is usually insignificant - no more than 1.0 g/day.

Modern methods studies reveal a number of changes in the microstructure of the kidneys, the consequence of which is the so-called physiological proteinuria. Based on such considerations, many authors doubt the validity of identifying “functional” proteinuria.

Pathological proteinuria

Pathological proteinuria can be of renal or extrarenal origin.

Renal proteinuria

Renal proteinuria is one of the most important and persistent signs of kidney disease and may be glomerular, or glomerular, And tubular, or canalicular. When these two types are combined, it develops mixed type proteinuria.

Glomerular proteinuria

Glomerular proteinuria caused by damage to the glomerular filter, occurs with glomerulonephritis and nephropathies associated with metabolic or vascular diseases. At the same time, plasma proteins are filtered from the blood into the urine in large quantities.

The dysfunction of the glomerular filter is based on various pathogenetic mechanisms:

1. toxic or inflammatory changes glomerular basement membrane (deposition of immune complexes, fibrin, cellular infiltration), causing structural disorganization of the filter;
2. changes in glomerular blood flow (vasoactive agents - renin, angiotensin II, catecholamines), affecting glomerular transcapillary pressure, convection and diffusion processes;
3. lack (deficiency) of specific glomerular glycoproteins and proteoglycans, leading to the loss of a negative charge by the filter.

Glomerular proteinuria is observed in acute and chronic glomerulonephritis, amyloidosis, diabetic glomerulosclerosis, renal vein thrombosis, congestive kidney, hypertension, nephrosclerosis.

Glomerular proteinuria can be selective or non-selective depending on the severity of damage to the glomerular filter.

Selective proteinuria

Selective proteinuria occurs with minimal (often reversible) damage to the glomerular filter (nephrotic syndrome with minimal changes), is represented by proteins with a molecular weight of no higher than 68,000 - albumin and transferrin.

Non-selective proteinuria

Non-selective proteinuria more common with more severe damage filter, is characterized by increased clearance of medium- and high-molecular plasma proteins (urine proteins also contain alpha2-globulins and gamma globulins). Nonselective proteinuria is observed in nephrotic and mixed forms glomerulonephritis, secondary glomerulonephritis.

Tubular proteinuria (tubular proteinuria)

Tubular proteinuria is associated either with the inability of the tubules to reabsorb proteins that have passed through the unchanged glomerular filter, or due to the release of protein by the epithelium of the tubules themselves.

Tubular proteinuria is observed in acute and chronic pyelonephritis, heavy metal poisoning, acute tubular necrosis, interstitial nephritis, chronic kidney transplant rejection, kalipenic nephropathy, genetic tubulopathies.

Extrarenal proteinuria

Extrarenal proteinuria occurs in the absence of a pathological process in the kidneys themselves and is divided into prerenal and postrenal.

Prerenal proteinuria

Prerenal proteinuria develops in the presence of an unusually high plasma concentration of a low molecular weight protein, which is filtered by normal glomeruli in an amount exceeding the physiological capacity of the tubules for reabsorption. A similar type of proteinuria is observed in myeloma (low molecular weight Bence Jones protein and other paraproteins appear in the blood), with severe hemolysis (due to hemoglobin), rhabdomyolysis, myopathy (due to myoglobin), monocytic leukemia (due to lysozyme).

Postrenal proteinuria

Postrenal proteinuria caused by the release of mucus and protein exudate in the urine due to inflammation of the urinary tract or bleeding. Diseases that may be accompanied by extrarenal proteinuria are urolithiasis, kidney tuberculosis, kidney or urinary tract tumors, cystitis, pyelitis, prostatitis, urethritis, vulvovaginitis. Postrenal proteinuria is often very minor and practically less important.

Proteinuria severity

Depending on the severity, mild, moderate and severe proteinuria are distinguished.

Mild proteinuria

Mild proteinuria(from 300 mg to 1 g/day) can be observed with acute infection urinary tract, obstructive uropathy and vesicoureteral reflux, tubulopathies, urolithiasis, chronic interstitial nephritis, kidney tumors, polycystic disease.

Moderate proteinuria

Moderate proteinuria(from 1 to 3 g/day) is observed in acute tubular necrosis, hepatorenal syndrome, primary and secondary glomerulonephritis (without nephrotic syndrome), proteinuric stage of amyloidosis.

Severe (pronounced) proteinuria

Under severe, or severe proteinuria define a loss of protein in the urine that exceeds 3.0 g per day or 0.1 g or more per kilogram of body weight in 24 hours. Such proteinuria is almost always associated with dysfunction of the glomerular filtration barrier in terms of protein size or charge and is observed in nephrotic syndrome.

Detection and quantitative assessment of proteinuria are important both for diagnosis and for assessing the course of the pathological process and the effectiveness of treatment. In conclusion, it should be noted that diagnostic value proteinuria is assessed in conjunction with other changes in urine.

Literature:

• L. V. Kozlovskaya, A. Yu. Nikolaev. Tutorial on clinical laboratory research methods. Moscow, Medicine, 1985
• A. V. Papayan, N. D. Savenkova "Clinical nephrology childhood", St. Petersburg, SOTIS, 1997
• Kurilyak O.A. "Protein in urine - methods of determination and normal limits ( current state Problems)"
• A. V. Kozlov, “Proteinuria: methods for its detection,” lecture, St. Petersburg, SPbMAPO, 2000.
• V. L. Emanuel, “ Laboratory diagnostics kidney diseases. Urinary syndrome", - Directory of the head of the KDL, No. 12, December 2006.
• O. V. Novoselova, M. B. Pyatigorskaya, Yu. E. Mikhailov, “Clinical aspects of identifying and assessing proteinuria”, Handbook of the head of the clinical laboratory, No. 1, January 2007.