Proteinuria is a phenomenon in which the protein is detected in the urine, which indicates the possibility of kidney damage, serves as a factor in the development of heart diseases, blood vessels, and lymphatic vessels.
What is protein in the urine( proteinuria)
Detection of protein in urine does not always indicate a disease. This phenomenon is typical even for absolutely healthy people, in urine which can be determined protein. Overcooling, exercise, eating protein foods leads to the appearance in the urine of a protein that disappears without any treatment.
During screening, a protein is detected in 17% of practically healthy people, but only 2% of this number of people is positive for the analysis of the kidney disease.
The function of preventing the loss of body protein molecules is performed by the kidneys.
Urinary filtration is performed by two renal systems:
- renal glomeruli - do not miss large molecules, but do not retain albumins, globulins are a fine fraction of protein molecules;
- renal tubules - adsorb proteins filtered by glomerulus, return back to the circulatory system.
Albumin( about 49%), mucoproteins, globulins are found in the urine, of which about 20% account for the share of immunoglobulins.
Globulins are whey proteins in a large molecular mass that are produced in the immune system and the liver. Most of them are synthesized by the immune system, refers to immunoglobulins or antibodies.
Albumins are a fraction of proteins that first appear in the urine even with minor renal lesions. A certain amount of albumin is also found in healthy urine, but it is so insignificant that it is not detected by laboratory diagnostics.
The lower threshold, which can be detected by laboratory diagnostics, is 0.033 g / l. If a day lost more than 150 mg of protein, then talk about proteinuria.
Symptoms of the protein in the urine
The disease with mild proteinuria occurs asymptomatically. Visually, urine that does not contain protein can not be distinguished from urine, in which there is an insignificant amount of protein. A somewhat frothy urine becomes already with a high degree of proteinuria.
It is possible to presume active excretion of protein in the urine according to the appearance of the patient only with an average or severe degree of the disease due to the appearance of swelling of the extremities, face, abdomen.
In the early stages of the disease, the indirect signs of proteinuria may be symptoms:
- changes in urine color;
- of increasing weakness;
- lack of appetite;
- nausea, vomiting;
- bone pain;
- drowsiness, dizziness;
- elevated temperature.
The appearance of such symptoms can not be ignored, especially during pregnancy. This may mean a slight deviation from the norm, or it may be a symptom of developing gestosis, pre-eclampsia.
Diagnosis
Quantitative assessment of protein loss is not an easy task, several laboratory tests are used to achieve a more complete picture of the patient's condition.
Difficulties in choosing a method for detecting excess protein in the urine are explained by:
- with a low protein concentration, which requires high-precision instruments to recognize;
- by the composition of urine, which complicates the task, since it contains substances that distort the result.
How to prepare for the
The greatest information allows you to get an analysis of the first morning portion of urine, which is collected after awakening.
On the eve of the analysis, the following conditions must be observed:
- not to consume spicy, fried, protein foods, alcohol;
- to exclude the use of diuretics for 48 hours;
- restrict physical activity;
- carefully observe the rules of personal hygiene.
Morning urine is the most informative, as it is in the bladder for a long time, less dependent on food intake.
Analyze the amount of protein in the urine can be by random portion, which is taken at any time, but such an analysis is less informative, the probability of error is higher.
Qualitative diagnostic methods for
The qualitative determination of proteinuria is based on the protein property of denaturing under the influence of physical or chemical factors. Qualitative methods refer to screening, allowing to establish the presence of protein in the urine, but not giving the opportunity to accurately assess the degree of proteinuria.
Samples are used:
- with boiling;
- with sulfosalicylic acid;
- with nitric acid, Larionova reagent at the ring Geller's test.
A sample with sulfosalicylic acid is performed by comparing a control urine sample with an experimental sample, in which 7-8 drops of 20% sulfosalicylic acid are added to urine. The conclusion about the presence of protein is made from the intensity of opalescent turbidity that appears in the tube during the reaction.
The Geller sample is often used with 50% nitric acid. The sensitivity of the method is 0.033 g / l. With this protein concentration in a test tube with a urine sample and a reagent, a white threadlike ring appears in the test for 2-3 minutes after the beginning of the experiment, the formation of which indicates the presence of protein.
Semi-quantitative
Semiquantitative methods include:
- method for determining the protein in the urine by test strips;
- method of Brandberg-Roberts-Stolnikov.
The method of determination by the Brandberg-Roberts-Stol'nikov method is based on the Geller ring method, but allows more accurate estimation of the amount of protein. When the test is carried out using this technique, several urine dilutions achieve the appearance of a threadlike protein ring in the time interval between 2-3 minutes from the beginning of testing.
In practice, the test strip method with the dye-applied bromophenol blue as an indicator is used. The disadvantage of the test strips is selective sensitivity to albumin, which leads to a distortion of the result in the case of a rise in the urine concentration of globulins or other proteins.
The disadvantages of the method are also the relatively low sensitivity of the test to the protein. React to the presence of protein in the urine test strip begins with a protein concentration exceeding 0.15 g / l.
Quantitative estimation methods
Quantitative estimation methods can be divided conditionally into:
- turbidimetric;
- colorimetric.
Turbidimetric methods
The methods are based on the property of proteins to reduce the solubility by the binding agent to form an insoluble compound.
Agents that cause protein binding can be:
- sulfosalicylic acid;
- trichloroacetic acid;
- benzethonium chloride.
Affect the evaluation of the intake of medications the day before, before the tests on these methods can not be taken:
- antibiotics;
- sulfonamides;
- iodine-containing preparations.
The method is available at cost, which allows it to be widely used for screening. But more accurate results can be obtained with the help of more expensive colorimetric methods.
Colorimetric methods
Sensitive methods that accurately determine the concentration of protein in the urine include colorimetric techniques.
Do it with high accuracy allow:
- biuret reaction;
- Lowry's technique;
- staining techniques, which use dyes that form complexes with urine proteins that differ from the sample visually.
Biuret reaction
The method refers to reliable, high sensitivity, allowing to determine in urine albumin, globulins, paraproteins. It is used as the main way to clarify the controversial results of the analyzes, as well as the daily protein in the urine in patients with nephrological departments of hospitals.
Lowry's method
Still more accurate results are achieved by Lowry's method, which is based on the biuret reaction, as well as the reaction of Folin, which recognizes tryptophan and tyrosine in protein molecules.
To avoid possible errors, the urine sample is purified by dialysis from amino acids, uric acid. Errors are possible with the use of salicylates, tetracyclines, chlorpromazine.
Painting Techniques
The most accurate method for determining protein is based on its ability to bind to dyes, of which:
- ponso;
- coomassie brilliant blue;
- pyrogallic red.
Daily proteinuria
During the day, the amount of protein excreted in the urine changes. To more objectively assess the loss of protein in the urine, introduce the concept of daily protein in the urine. This value is measured in g / day.
For a quick assessment of the daily protein in the urine, the amount of protein and creatinine is determined in a single portion of urine, then the protein / creatinine ratio is taken as the protein loss per day.
This method excludes possible errors that may occur during the collection of daily urine.
Decoding of the results of
Qualitative tests more often than quantitative tests give false positive or false negative results. Errors arise in connection with taking medication, eating habits, physical exertion on the eve of the analysis.
Sulfosalicylic acid test
The decoding of this quality test is based on a visual assessment of turbidity in a test tube when comparing the test result with a control test:
- a weakly positive reaction is estimated as +;
- positive ++;
- sharply positive +++.
Geller assay
Geller's ring test more accurately assesses the presence of protein in the urine, but does not allow quantitative assessment of protein in the urine. Like the test with sulfosalicylic acid, Heller's test gives only an approximate idea of the protein content in urine.
Test of Brandberg-Roberts-Stolnikov
The method allows to assess the degree of proteinuria quantitatively, but too laborious, inaccurate, as with a strong dilution the accuracy of the evaluation is reduced.
To calculate the protein, multiply the urinary dilution by 0.033 g / l:
| Amount of urine( ml) | Volume of water( ml) | Breeding | Protein content( g / l) |
|---|---|---|---|
| 1 | 1 | 1: 2 | 0,066 |
| 1 | 2 | 1: 3 | 0.132 |
| 1 | 4 | 1: 5 | 0.165 |
| 1 | 5 | 1: 5 | 0.198 |
| 1 | 6 | 1: 7 | 0.231 |
| 1 | 7 | 1: 8 | 0.264 |
| 1 | 8 | 1: 9 | 0.297 |
| 1 | 9 | 1:10 | 0.33 |
Testing the test strip
Testing does not require special conditions, this procedure is easy to do at home. To do this, the test strip should be lowered into the urine for 2 minutes.
The results will be expressed by the number of pluses on the strip, the decoding of which is contained in the table:
| Concentration( mg / 100 mL) | 10 | 20 | 30 | 100 | 300 | 2000 |
|---|---|---|---|---|---|---|
| Designation | Not determined | traces | 1+ | 2 ++ | 3 +++ | 4 ++++ |
- Resultstesting, corresponding to a value of up to 30 mg / 100 ml correspond to physiological proteinuria.
- The values on test strips 1 + and 2 + 2 mean significant proteinuria.
- Values of 3 +++, 4 ++++ are noted in pathological proteinuria caused by kidney disease.
The test strips allow only approximately to determine the elevated protein in the urine. For accurate diagnosis they do not use, and even more so they can not say what it means.
Do not allow test strips to adequately assess the amount of protein in the urine in pregnant women. A more reliable method of evaluation is the determination of protein by daily urine.
Determination of urinary protein by test strip:
Total urinary protein
Daily urine protein serves as a more accurate diagnostic for assessment of renal functional status. For this, it is necessary to collect all the urine secreted by the kidneys per day.
Protein content in urine can be determined by the protein: creatinine ratio, the data is given in the table:
| Proteinuria grade | Causes of | Daily urine, g / day | Urine per minute mg / min |
|---|---|---|---|
| light | acute infection, uropathies, polycystosis, tubulopathy | 0, 3 - 1 | less than 20 |
| median | tubular necrosis, glomerulonephritis, amyloidosis | 1 - 3 g | from 20 to 200 |
| expressed | nephrotic syndrome | more than 3 g | more than 200 |
The values given in the table for the protein / creatinine ratio are as follows:
| Children under 2 years of age | Children after 2 years of age, adults | |
|---|---|---|
| protein / creatinine | less than 0.5 | less than 0.2 |
With loss of more than 3.5 grams of proteina day the condition is called massive proteinuria.
If a lot of protein in the urine requires a re-examination after 1 month, then 3 months later, according to the results, which establishes why the rate is exceeded.
Causes of
The causes of increased protein in the urine are its increased production in the body and disruption of the kidneys, distinguish between proteinuria:
- physiological - minor deviations from the norm are caused by physiological processes, are resolved spontaneously;
- pathological - changes are caused by a pathological process in the kidneys or other organs of the body, without treatment progresses.
Physiological Proteinuria
A slight increase in protein can be observed with abundant protein nutrition, mechanical burns, trauma accompanied by increased production of immunoglobulins.
An easy degree of proteinuria can be caused by physical exertion, psycho-emotional stress, taking certain medications.
Kidney diseases, infectious diseases are also sometimes accompanied by the appearance of a protein in the urine.
Similar conditions usually correspond to an mild degree of proteinuria, are transitory phenomena, quickly pass on their own without requiring special treatment.
Pathological proteinuria
More severe conditions, expressed proteinuria, are noted in the case of:
- glomerulonephritis;
- diabetes;
- heart disease;
- bladder cancer;
- multiple myeloma;
- infection, drug damage, polycystic kidney disease;
- high blood pressure;
- systemic lupus erythematosus;
- Goodpasture syndrome.
To cause traces of protein in the urine may be intestinal obstruction, heart failure, hyperthyroidism.
Classification of
The varieties of proteinuria classify in several ways. For a qualitative evaluation of proteins, you can use Yaroshevsky's classification.
According to the systematics of Yaroshevsky, established in 1971, proteinuria is distinguished:
- is renal - which includes infringement of glomerular filtration, isolation of tubular protein, inadequate reabsorption of proteins in tubules;
- prerenal - occurs outside the kidneys, removing from the body hemoglobin, proteins that arise in excess in the blood as a result of multiple myeloma;
- postrenal - occurs on the urinary tract after the kidneys, excretion of the protein in the destruction of urinary organs.
For the quantitative evaluation of the event, the degree of proteinuria is conventionally determined. It must be remembered that they can easily move into a heavier one without treatment.
The most severe stage of proteinuria develops with the loss of more than 3 g of protein per day. The loss of protein from 30 mg to 300 mg per day corresponds to a moderate stage or microalbuminuria. Up to 30 mg of protein in daily urine means a mild degree of proteinuria.