PROTEINURIA (proteinuria; + Greek uron wetting proteins) — release of protein with urine. In diagnostic practice the term is used in value of a symptom and corresponds to detection of protein in urine in concentration 0,033 °/00 and above, i.e. available to definition by usual laboratory methods (see. Brandberga-Robertsa-Stolnikova method ). The term «proteinuria» is more exact, than the term «albuminuria» used earlier in the same value since as a part of the protein secreted with urine there are its various fractions.
At almost healthy adults per day in primary urine 30 — 50 g of protein which almost reabsorbirutsya completely in proximal renal tubules are filtered, and in the daily volume of final urine its maximum quantity does not exceed 150 mg (no more than 30 mg usually contain). At a research of urine (see) in polyacrylamide gel in it prealbumins, albumine, post-albumine, transferrin, globulins are found. At an immunoelectrophoretic research (see. Immunoelectrophoresis ) the concentrated urine a number of the proteins similar in the antigenic relation is allocated to serum proteins: prealbumin, albumine, an alfa1-acid glycoprotein, alfa1-antitrypsin, ceruloplasmin, transferrin, immunoglobulins and other proteins, in particular uromukoid, the pretsipitatsionny line to-rogo passes through all zone of alfa1-globulins.
Penetration of various proteins into urine depends as on a condition of the glomerular filter and proximal renal tubules, and on the molecular weight of protein, its charge and a form. So, the myoglobin (see) having the relative molecular mass 17 500 is filtered for 75%, and hemoglobin (relative molecular mass apprx. 65 000) — for 3% (see. Haemoglobinuria , Myoglobinuria ). With - D - ceruloplasmin (relative molecular mass 125 000) is almost not filtered. At the same time C-C - the ceruloplasmin having high relative molecular mass (143 000) is filtered almost completely.
The item can incidentally come to light at almost healthy faces in connection with the use of protein-rich food, especially large amount of crude ovalbumin (alimentary P.), after bathing in a cold water, big physical activity, including after the long marches (so-called mid-flight P.).
At patol. processes and P.'s conditions it can be connected with damage of kidneys (renal P.) or to have an extrarenal origin (prerenalny and prerenal P.).
To proximate causes extrarenal Item. belong: 1) emergence and strengthening in blood of the low-molecular proteins which are easily filtered in balls of kidneys (prerenalny P.) that is observed at diseases of blood, hemolysis, a multiple myeloma, extensive injuries of the muscles which are followed by a myoglobinuria, burns after intensive insolation (proteinuria solaris); 2) release of protein from the breaking-up leukocytes, epithelial and other cells in uric ways (prerenal P.) at their inflammation, tumors, a spermatorrhea, etc. — so-called accidental P.; 3) disturbances of a renal hemodynamics which hold a specific place among P.'s reasons since also dysfunction of nephrons participates in an origin of the last along with extrarenal factors quite often (e.g., their ischemic damage at hypertensive crises). Most often such P. is observed at heart failure (so-called congestive P.) and other states which are followed by build-up of pressure in renal veins, in particular at a lumbar lordosis (so-called lordotic P.). In the majority of these cases of P. arises or accrues in the conditions of an ortostaz.
If P. comes to light only after long standing, it call orthostatic. As independent allocate orthostatic P., quite often observable at adynamic young faces (as a rule, in the presence of a lordosis) and passing with age. For identification of inspected by orthostatic P. ask to empty a bladder in the morning right after a dream and in an hour, without getting up; protein is defined the last portion of urine and in urine, collected then after hour stay in an ortostaza. Results of a puncture biopsy of kidneys (see) show that orthostatic P. can be display of their pathology. In doubtful cases the Item needs careful inspection of persons with orthostatic.
Item of pregnant women, arising at some women in the last three months of pregnancy, it is also usually connected with build-up of pressure in renal veins and predictively it is favorable. It should be distinguished from a nephropathy of pregnant women (see) — the late toxicosis of pregnancy which is followed by damage of kidneys.
As a symptom of a disease of kidneys P. is known since R. Brayt's researches. At the end of 19 — the beginning of 20 centuries the question of primacy of a proteinuria was discussed, to-ruyu many researchers considered as the reason, but not a consequence of a disease of kidneys. This point of view in an essential measure was confirmed at a multiple myeloma, at a cut damage of kidneys is most often connected with adjournment of precipitated calcium superphosphates of myelome proteins in renal tubules though also the immunocomplex nephropathy proceeding as a glomerulonephritis is possible.
Renal Item. pathogenetic it is connected preferential or with disturbance of permeability for protein of membranes of balls of kidneys (glomerular P.) that is observed at fever, toxic injuries and other diseases of kidneys, or with disturbance of a reabsorption of protein in proximal renal tubules (canalicular P.), a cut prevails in P.'s genesis at some fermentopatiya, intersticial nephrite, toxic nefropatiya. The canalicular proteinuria is usually insignificant also a nizkomolekulyarna. At very heavy damages of nephrons to P.'s origin also release of protein in urine through walls of renal tubules plays a role. At the majority of diseases of kidneys, including at a glomerulonephritis, poisoning with salts of heavy metals, etc., glomerular and canalicular factors of an origin of P. are combined.
Because P.'s reasons are diverse, its diagnostic value is limited. Nevertheless assessment of this symptom in dynamics gives sometimes valuable diagnostic and predictive information, and in certain cases P. happens one of the first symptoms of a disease (e.g., at a nephropathy of pregnant women), detection to-rogo is a reason for the developed diagnostic inspection of the patient. At a wedge, P.'s assessment take into account circumstances of its emergence, constancy or frequency of manifestation, a combination to other symptoms and change of composition of urine (a hamaturia, a cylindruria, a pyuria, etc.). Also quantitative assessment of the Item matters. At lordotic, congestive and in most cases feverish P., and also at pyelonephritis concentration of protein in urine seldom exceeds 1 ‰; at a nephropathy of pregnant women, a glomerulonephritis, a nephrotic syndrome higher concentration of protein is usually noted. At the same time there is no obligatory compliance between a form of pathology and degree of P., napr, at a glomerulonephritis (both acute, and chronic) P. can be very expressed, but maybe absolutely be absent. There is no parallelism and between P.'s degree and weight of damage of kidneys that reduces its predictive value. It can be very considerable at a lipoid nephrosis (morfol, option of a glomerulonephritis) — a disease with the good forecast, and extremely insignificant at the heaviest terminal damages of kidneys.
Nek-roye the research of proteinaceous composition of urine in starched or polyacrylamide gel, by means of paper electrophoresis matters (see. Electrophoresis ), the immunochemical methods allowing to determine by P. as the selection or non-selective. Assessment of selectivity of P. is carried out by calculation of clearance (see) two proteins with different molecular weight — albumine or transferrin and (molecular weight 150 000). Calculate an index of selectivity on the attitude of clearance of high-molecular protein towards clearance of low-molecular protein. At non-selective proteinurias this index higher than 0,2. There are also other, more difficult methods of calculation of selectivity of P. with the graphic representation of clearance of several proteins percentage of clearance of any standard protein, napr, albumine. Carry P. caused by release of protein with a molecular weight below 80 000 to the high-selection (albumine prevails, smaller quantities contain siderophilin and an a1-glycoprotein, and clearance gamma globulinovoy to fraction it is equal to about 10% of clearance of albumine). At the low-selection P. the clearance gamma globulinovoy fractions approaches 50% of clearance of albumine (a so-called globulinuria), in urine find practically all plasma proteins. Researches at a glomerulonephritis and a nephrotic syndrome of a different etiology in general confirm opinion that to bigger weight of damage of kidneys there corresponds lower selectivity of the Item. Though such compliance is very relative, definition of selectivity of P. is tried to be used for assessment of efficiency of therapy. So, according to M. A. Ado et al. (1977), bystry (during 1 — 2 week) decrease in clearance of albumine with the subsequent decrease in clearance predictively is favorable.
Irrespective of the nature of damage of kidneys loss of a large amount of protein in connection with P. can lead to development of a nephrotic syndrome with inherent to it heavy a wedge, a picture since possibilities of compensation of losses of protein do not exceed 5.5 g of albumine a day.
The proteinuria at children
the General daily excretion of proteins with urine at the healthy child seldom reaches 150 mg and usually makes 20 — 75 mg, and in urine almost all proteins of a blood plasma, except for macroglobulins, a gaptoglobulin, ceruloplasmin and beta lipoproteins are found. According to daily change of an active reabsorption in proximal renal tubules excretion of protein in morning p day time at healthy children is lower, than in the evening and at night. In the afternoon protein in urine at healthy children by means of usual a lab. methods, as a rule, are not defined.
Tranzitorny P. happens at newborn children, especially at premature, at an insufficient maturity of renal structures. Pathological P.'s reasons generally the same, as at adults, but are available for children the distinctions in their relative frequency reflecting features of structure of renal pathology at children. The canalicular P. caused by hereditary or inborn pathology (a disease and de Tony's syndrome — Debra is slightly more often observed — Fankoni, renal a dysplasia), meets the prerenal P. connected with diseases of uric ways much less often.
More expressed P. is noted at fever, and at a number of nurseries inf. diseases it can be very considerable. At diphtheria, e.g., concentration of protein in urine in some cases reaches 20 °/00. Moderate P. (loss to 3 g of protein per day) is often observed at a glomerulonephritis and, as a rule, combined with a hamaturia and an abacterial leukocyturia. The expressed P. (loss more than 3 g, sometimes to 100 g of protein per day) is characteristic of a nephrotic syndrome of different genesis. P.'s combination to arterial hypertension demands an exception of tumoral process and anomaly of renal vessels. Existence along with P. of dysuric frustration, a leukocyturia serves as the indication to inspection for an exception of an obstructive uropathy. The item at the general dystrophy of the child with the expressed bone changes obliges to exclude that-bulopatiyu. The moderated, accidentally revealed P. with unsharp changes in draft' urine demands an exception of a renal dysplasia.
Predictive value P. at diseases of kidneys at children is as limited, as at adults. Consider that at a glomerulonephritis the resistant, accruing proteinuria (especially with a cylindruria and a hamaturia) predictively is adverse.
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V. V. Sura; M. S. Ignatova (ped.).