Clinical analysis of urine is a widely used and widespread study that can be performed in health care facilities, including the office of a local (family) GP, in emergency rooms, medical laboratories, and even at home.
General urine analysis, abbreviated as OAM, is an affordable and inexpensive, but quite informative method for diagnosing various pathological conditions and diseases. Some doctors even call OAM “cheap kidney biopsy” because of the large amount of information that can be obtained about their health or other internal organs with this simple test.
Urine is evaluated according to its appearance (macroscopically): color, transparency / turbidity, smell - and microscopically (molecular properties, quantitative and qualitative ratio of chemical elements in it, sediment research).
Direction for analysis
OAM is prescribed by doctors for a number of reasons, including:
- During a routine medical examination: annual physical examination, preoperative examination, at the initial admission to the clinic, for monitoring kidney diseases, diabetes, hypertension (high blood pressure), liver diseases, etc.
- To evaluate individual symptoms: abdominal pain, painful urination (dysuria), lower back pain, fever, blood in the urine (hematuria) and other urological symptoms.
- When diagnosing internal pathologies: bacterial cystitis and nephritis, kidney stones (nephrolithiasis), uncontrolled diabetes mellitus (type 2), kidney disease, myositis (muscle inflammation), protein in the urine (proteinuria), screening for drug excretion and inflammation kidney (glomerulonephritis).
- To monitor disease progression and treatment dynamics (response to therapy).
- When determining pregnancy.
The decrypted result of a urinalysis can identify diseases that go unnoticed, since they do not cause obvious clinical signs (visible symptoms). Such diseases include: diabetes mellitus, interstitial and hypertonic glomerulonephritis and chronic genitourinary infections.
The most economical urine screening device is a paper or plastic indicator strip. The measuring system of dry microchemistry has been available for many years and allows for clinical analysis of urine within a couple of minutes. Now we will dwell in more detail on each of the existing research methods and the interpretation of urine tests in the table.
Methods of collecting urine
To perform the test, it is necessary to collect a urine sample from the patient in a special container. Usually a small volume of liquid is required (about 30-60 ml). The study can be carried out both in a conventional medical center and in a laboratory. There are several methods of collecting material:
- Arbitrary collection at any time of the day without special preparation to prevent contamination (clogging) of the material. The collected urine can be weakly concentrated, isotonic, or hypertonic (depending on the amount of salts dissolved in it) and may include white blood cells (white blood cells), bacteria, and squamous epithelium as contaminants (impurities). In females, the sample may contain vaginal discharge, bloody inclusions during the menstrual cycle, as well as Trichomonas and yeast.
- Urine solution collected early in the morning on an empty stomach. Usually, such a portion is hypertonic (highly concentrated) and reflects the function of the kidneys to slow down the formation of urine at night (dehydration after sleep). If you stop taking food and water after 6 pm, then the next morning the density of urine in the norm may exceed 1.025.
- Clean, middle urine is collected after rinsing the external urethra. To do this, any cotton fabric moistened with 0.9% isotonic saline is suitable. The average portion is the one in which the first stream of urine is passed, and the last half of the stream of urine is collected in the container. The first jets are used to flush the urinary tract from contaminants.
- The introduction of a urological catheter into the cavity of the bladder through the lumen of the urethra is carried out only as a last resort, when the patient is in a coma or unconscious. Since this procedure has a high risk of infection, injury to the urethra and the bladder wall, which leads to iatrogenic (due to the doctor’s fault) drift of pathogenic microbes or bloody, painful urination.
- Transabdominal aspiration of the bladder (cystocentesis). In this case, the needle is inserted into the cavity, piercing the abdominal wall, and the necessary portion is taken into the syringe. Subject to all the rules of asepsis / antiseptics, the resulting urine is almost sterile from microorganisms. Cystocentesis is highly used in decoding urinalysis in children.
Macroscopic indicators of urine
There are several of them. When deciphering the result of urine analysis (the norm is in the table at the end of the article), its visual component is first evaluated, that is, what is visible to the naked eye. Normal, fresh urine has all possible shades of yellow and amber colors with pronounced transparency. The physiological volume of daily urine varies from 700 ml to 2 liters.
Opalescence (turbidity) appears with excessive cellular material or with abundant protein content in the urine. Turbidity of the urine is also visible in violation of the terms and methods of storing the material at different temperature conditions, the longer the urine is stored, the more it crystallizes and precipitates salts.
Redness with a brownish tinge indicates an admixture of food or drug dyes, the presence of hemoglobin or myoglobin. Blood in the urine is also one of the main causes of not only its redness, but also turbidity.
The therapist can simply perform an express test with a strip at the reception. It only takes a few minutes. And at the same time, the doctor can send one middle part of the urine to the laboratory for cultural research (sowing urine). To decipher the result of a urine test of this test, it will take several working days. The results of the sowing will show the attending physician which specific bacteria caused the infection, and to which antibiotics this type of microorganism is sensitive and resistant.
This test should also be accompanied by other types of studies. Additional tests and clinical evaluation are often necessary to objectively decipher the analysis of urine in adults and elderly patients and, ultimately, for making a diagnosis. For example, UTI (urinary tract infection) is usually diagnosed according to the table of norms for decoding urinalysis in adults. However, a culture test is more often performed as a control test to identify specific microbes and confirm the diagnosis.
Who is studying the information
Deciphering the results of a urinalysis, as a rule, is based on the study of all components of the test and comparing it with clinical signs and physical examination. Decryption is carried out by the attending physician who prescribed the examination. Nevertheless, independent study of the results is also acceptable.
Urinalysis with a test strip
An express test is a paper strip with indicator marks soaked in chemicals that change color in the presence of certain components of urine in a certain concentration. The intensity of staining depends on the concentration of these substances. The strip is immersed in a urine sample and after a few seconds it is removed and compared with the color scale on the package to decode the urinalysis.
pH
Filtered plasma through the renal glomeruli acquires an acidic environment ranging from 7.6 to 5.8 in the final urine. If the acid-base state of the blood is different, then the pH of the urine can vary from 4.4 to 8.1. Deviations of this parameter from 7.5 are carried out in the descending collecting ducts and the collecting channel of the kidneys.
Specific gravity
The specific gravity (or density) of urine is determined by the presence of substances dissolved in it, represented by particles of various sizes, from small ions to larger proteins. Urine osmolarity measures the total amount of solute, regardless of size. The most common method is to lower the freezing point of urine. A refractometer measures the change in direction of the light path (refraction) based on the concentration and size of particles in a liquid. Larger elements, such as glucose and albumin, will change the refraction to a greater extent. Measurement of the specific gravity of the express test strip is approximate, so you should not completely trust this indicator as a result of the analysis.
Normal specific gravity is considered in the reference value from 1.004 to 1.036, in the absence of renal pathologies. Since the specific gravity of primary urine in the Bowman capsule is from 1.004 to 1.008, a decrease in it indicates a high level of fluid, and an increase in dehydration.
If in the absence of food intake for 8-10 hours and water for 2 hours before taking the analysis, the density of urine is lower than 1.020, this means that the filtering ability of the kidneys decreases, which happens with generalized renal failure or renal diabetes. In the later stages of the disease, the density of urine becomes from 1.005 to 1.008.
If, when decoding the analysis of urine in adults according to the table, its specific gravity is more than 1.037, or the shelf life of urine is violated, it contains a large amount of glucose impurities. During excretory intravenous urography, when a contrast medium is injected into a vein, its density also changes.
Protein (Protein)
Semi-quantitative screening of urine for the protein content in it should be carried out using laboratory equipment, since the test strip often gives a falsely high protein score. Normal normal protein excretion in adults does not exceed 150 mg per day or 10 mg / 100 ml in one sample. More than 150 mg per day is defined as proteinuria. Proteinuria> 3.5 g per day is a very serious condition - nephrotic syndrome.
Glucose (Glucose)
Normally, less than 0.1% glucose is present in urine (<130 mg / 24 hours). Glucosuria (excess sugar in the urine) generally means diabetes. In this case, a test strip test is considered a reliable determination of glucosuria.
Ketone bodies
Ketone bodies (acetone, acetoacetic acid, beta-hydroxybutyric acid) appear in the urine as a result of diabetic ketosis or with prolonged starvation. Easily detected using a conventional rapid test. Normally, ketone bodies should not be in the urine.
Nitrogen (Nitrite)
A positive nitrite test indicates that a significant amount of nitrogen-forming bacteria is present in the urine. Gram-negative bacilli, such as E. coli (E. coli), are more likely to give a positive result.
White blood cells (WBC - white blood cells)
A positive reaction to white blood cells is due to the presence of white blood cells in the urine (pyuria, white blood cells). This reaction also indicates an active inflammatory process or infection. A negative result is deciphered by the low probability of infection.
Microscopic analysis of urine
A precipitate is prepared from the obtained urine sample, and then a small and large magnification study is performed using a microscope. This method can detect epithelial cells, crystals of kidney and urinary stones, bacteria, blood cells and other objects.
Red blood cells (RBC - red blood cells)
Hematuria - the presence of an abnormal number of red blood cells in the urine due to damage to the renal glomeruli, tumors of the urinary tract, kidney injuries, urinary stones, kidney infections, acute tubular necrosis, UTI, nephrotoxins and physical stress. Theoretically, normally, not a single red blood cell should be found in urine sediment, but sometimes it is found in small numbers in healthy people.
Epithelial cells
In chronic nephrosis, the total amount of renal and urinary epithelium is deposited on the bottom of the urine. Physiologically acceptable low epithelium content.
Leukocyte casts in urine sediment are most characteristic of acute inflammation of the renal pelvis, but are also detected with glomerulonephritis, since they are formed only in the kidneys.
In the terminal (last) stage of renal failure, any urinary inclusions are practically absent, since the remaining small living kidney cells cannot produce concentrated urine.
Crystals
Ordinary crystals are visible in the urine sediment even in the absence of urolithiasis, they include: calcium oxalates, tripelfosphates and amorphous phosphates.
Atypical crystals include cystine formations in the analysis of urine of newborn children, which indicate congenital liver failure, and tyrosine crystals in a child indicate a serious liver disease.
Interpretation of Results
The table below shows the decryption of the general analysis of urine is normal.
So the test indicators are deciphered when they are normal.