The presence of protein in the urine or proteinuria does not mean that the protein is necessarily of renal origin. Consequently, the appearance of protein in the urine is not always an indication of kidney damage. The urine of a healthy person does not contain protein, or its content does not exceed 0.03 g / l (according to some authors, the urine is always a small amount, about 0.08 grams of protein, and the norm is 0.14 g / l of protein in the urine. Up to content). Albumin is usually excreted in the urine from the two major fractions of blood protein.
Due to this, in case of prolonged proteinuria, not only hypoproteinemia (low protein content in the blood) is observed, but also a decrease in the blood protein coefficient (the blood protein coefficient is the ratio of the percentage of albumin to the percentage of globulins). In the urine, primarily low-molecular-weight proteins are excreted, while excretion of high-molecular-weight proteins by the kidneys occurs only after their pre-degradation. The latter is produced by renal filtration and reabsorption (absorption) under the influence of enzymatic and other processes, so albumin is always found in the urine. Their content reaches 70 and more percent of urinary protein, while the percentage of globulin fraction is much lower and highly variable, so the presence of protein in urine, in addition to proteinuria, is also referred to as albuminuria. Globulinuria is the high content of globulin fraction in urine during albuminuria. It is also noteworthy that up to 20 protein fractions are found in the urine of healthy people. These include prealbumin, albumin, postalbumin, siderophyllin, ceruloplasmin, heptaglobin, immunoglobulins A, G, and others. Distinguish between false and true (renal) albuminuria. The latter, in turn, may be physiological, functional, and pathological. In addition to the usual protein, which consists of sulfur albumin and sulfur sulfobulin, in some cases in the urine may appear acetic acid-protein body and the so-called. Bens-Jones protein body as well.
The appearance of protein in the urine during false albuminuria is not always the result of its elimination (excretion) by the kidneys. Protein in urine may be mixed with:
- During inflammatory (catarrhal) processes from the urinary tract;
- Due to purulent processes from the renal vials;
- From the ureters
- From the bladder.
Protein in the urine may be the result of a mixture of menstrual blood or vaginal discharge. In such cases the protein content does not exceed 1%.
Is physiological albumin
Physiological albuminuria includes cases of temporary proteinuria that are not associated with disease. Such albuminuria may also develop in healthy people from foods rich in non-denatured proteins (raw eggs, boiled milk, etc.). After receiving. It is also called alimentary albuminuria. Most often physiological albuminuria develops after intense muscle tension, long journeys, sports competitions, as well as – after a cold shower and bath. Generally, the appearance of protein in the urine due to a cold is explained by a reflex disorder of the blood circulation in the kidneys. The same mechanism of proteinuria is thought to be activated under conditions of intense insolation when a strong skin reaction to insolation develops. Physiological albuminuria may occur during concussion as well as in the post-epileptic seizure period (so-called centrogenic albuminuria). The cause of physiological albuminuria is often strong emotion. The so-called Emotional albuminuria is observed, for example, in entrants and students due to strong nervous tension during exams.
Functional albuminuria refers to cases of protein production in the urine that are not even related to organic kidney disease, but are caused by certain functional disorders in the body. Functional albuminuria is primarily attributed to cyclic or, as it is called, orthostatic albuminuria. His example is also congestive and allergic albumin. Functional albuminuria is also manifested in various mental and nervous diseases. Orthostatic or adolescent albuminuria is most common in children and adolescents (7 to 15 years). At such times, it is usually difficult to determine the nature of albuminuria. This type of albuminuria is usually seen in weak, pale, children and adults with headaches. Congestion processes in the kidneys during cardiac decompensation can also lead to functional albuminuria. Albuminuria is sometimes the result of pressure on the inferior vena cava during a pathological process.