Urinalysis is a comprehensive study, during which the general properties of urine, its physico-chemical characteristics are determined, and sediment microscopy is performed. Urinalysis refers to routine methods, is carried out during preventive examinations, as well as as part of a comprehensive diagnosis of diseases of various profiles, in particular, pathologies of the urinary system. The research finds application in general therapeutic practice, in pediatrics, urology, nephrology, surgery and other fields of medicine. A biomaterial is an average portion of urine collected in the morning after waking up. The study is carried out by organoleptic methods, methods of “dry chemistry” and microscopy. Normally, the urine is transparent, without a sharp smell and impurities, single blood cells and cylinders are acceptable. The analysis is performed in 1 day.
Urinalysis is one of the most common methods of laboratory diagnostics. It is used for preventive examinations of large groups of people, for the initial treatment of patients for medical care, for monitoring diseases of various etiologies. The connection between changes in urine characteristics and the development of diseases was first noted by Hippocrates. Ancient sources of Indian and Chinese medicine have preserved information about the importance of studying this biological fluid in identifying various pathologies, in particular, diabetes mellitus. For a long time, urine analysis was based on a visual comparison of the physical characteristics of a sample of a sick person with a healthy sample as a reference.
A leap in the development of laboratory diagnostics, including in the study of urine, occurred in the XVII-XVIII centuries. At that time, the first microscope, colorimeter was invented, a cell of a living organism was discovered and studied, knowledge in related fields was accumulated: chemistry, engineering, biology. In the first half of the XIX century, microscopic studies of urine sediment were performed for the first time in clinical and laboratory conditions, diagnostic tables and methodological manuals for laboratory assistants were created on their basis. Soon colorimetry began to be actively used in practice. From the middle of the XX century to the present, the development of laboratory diagnostics, including urinalysis, is on the way to improving the quality of research: the sensitivity of tests increases, their reproducibility. Thanks to the development of technologies, automated and semi-automated analyzers are being introduced into practice, which reduces time and labor costs when performing research.
To date, the general analysis of urine is used in almost all areas of medicine. Its results are used in general therapeutic and pediatric practice, in urology, nephrology, gastroenterology, cardiology, neuropathology, surgery, endocrinology, obstetrics and gynecology. The analysis includes tests of several groups. Organoleptic examination involves the determination of daily diuresis, color, odor, foaming and transparency. When performing physico-chemical tests, the density and acidity of urine are evaluated, when conducting biochemical tests – the amount of protein, glucose, ketones, bilirubin, bile acids. Microscopy of sediment is aimed at detecting erythrocytes, leukocytes, epithelial cells, cylinders, salts, bacteria. Based on the results of urinalysis, the doctor concludes about the patient’s health status. Often, the obtained indicators are interpreted in combination with the data of general and biochemical blood tests.
Urinalysis is performed as part of a comprehensive diagnosis during preventive examinations. It is prescribed during occupational examinations, during pregnancy monitoring, during the passage of a medical commission for military service, etc. The range of indications for urinalysis is very wide, the study is carried out during the primary diagnosis and monitoring of infections, diseases of the gastrointestinal tract, cardiovascular and respiratory systems, and metabolic pathologies. Its results are used to control acute conditions – after intoxication, injuries, burns, complications of diseases with bleeding, inflammation, perforation of the walls of organs.
A special indication for the general analysis of urine are pathologies of the kidneys and urinary tract. The results make it possible to differentiate various diseases of this group, evaluate the effectiveness of treatment, identify exacerbation, and make a prognosis. The basis for the appointment of the study are specific symptoms: the transparency and / or color of urine changes, the frequency of urination is disturbed, they become difficult, often painful, swelling, pain in the lower abdomen and lower back appear, the temperature rises. If deviations are determined in the test results, then additional studies are assigned to establish the diagnosis. In order to monitor kidney function, the study is indicated when taking nephrotoxic drugs.
The limitations of the general urinalysis include its low specificity. The deviation of certain indicators is characteristic of several diseases or conditions at once. Sometimes, based on the results of the analysis and clinical manifestations, the doctor manages to establish a diagnosis, sometimes more accurate data is required, additional tests are prescribed (urine analysis according to Nechiporenko, two-glass sample, Rehberg test, etc.). Despite this, the study is widespread in medical practice, since the studied indicators reflect the peculiarities of the functioning of most organs and systems of the body, and the analysis procedure itself does not require large time and labor costs.
Preparation and collection of urine
When performing a general urine test, the average portion of the material collected in the morning is examined. 2 days before the analysis, it is necessary to cancel the intake of diuretics, 1 day before – exclude alcohol, products with dyes, high salt content from the diet, and also limit physical activity. If at the time of the study the patient is taking any medications, then their effect on the indicators of the general urinalysis should be discussed with a doctor. Urine collection is performed in the morning. Immediately after waking up, it is necessary to thoroughly wash and wipe the external genitals. Women cannot collect urine independently during menstrual bleeding and 1-2 days after it, the procedure can be performed on an outpatient basis using a catheter. Also, the collection of biomaterial is prohibited for several days after invasive procedures on the bladder.
For general analysis, an average portion of morning urine is collected in a sterile container, the first and last portions are sent to the toilet. The biomaterial can be stored for no more than 1.5 hours in a container with a closed lid. In the laboratory, the study is carried out in several stages. First, with the help of organoleptic methods, that is, with the help of sensory organs, the physical properties of urine are evaluated – the features of color and smell, transparency are determined. A urometer measures the specific gravity of urine. Biochemical research is carried out by methods of “dry chemistry– – using test strips: a urine sample is applied to them, and then a qualitative and semi-quantitative assessment of the result is made using photometers. For microscopic examination, the preparation is prepared on a slide, the number of blood cells, cylinders, epithelial cells is counted, the presence of salts is determined. The analysis is performed within 1 working day.
When performing a general analysis, the urine color is normal from straw yellow to yellow, the sample is transparent, without a sharp smell. Density from 1003 to 1030 g / l, pH (acidity) from 5 to 7 units. The protein concentration should not exceed 0.140 g / l, glucose, bilirubin, ketone bodies, nitrites are not detected, trace values of urobilinogen are possible. Microscopic examination is normal in the field of vision:
- in men – up to 3 leukocytes, in women and children – up to 5-6 leukocytes;
- up to 2 red blood cells;
- in men – up to 3 cells of the squamous epithelium, in women – up to 5 cells of the squamous epithelium;
- no more than 1 transitional epithelial cell;
- renal epithelial cells are not detected;
- cylinders are not defined;
- bacterial cells are not detected;
- salt crystals are not detected.
Physiological factors can lead to some distortion of the results of the general urine analysis and their deviation from the norm: intense physical activity, emotional stress, excessive consumption of liquids, salty food, alcoholic beverages, coffee. So, physical exercises and experiencing strong emotions on the eve of collecting urine lead to the appearance of cylinders in it, an increase in the number of red blood cells. When following a protein diet, excess proteins are excreted through the kidneys – protein is detected in the urine. A diet with a predominance of animal food leads to an increase in the acidity of urine, and a plant-milk diet leads to an increase in alkalinity. Some foods, such as beets or carrots, change the color of urine, and an increase in the volume of fluid consumed affects its specific gravity.
Deviations from the norm
Urinalysis is one of the most popular studies in clinical practice. Its main advantages are cost-effectiveness and high information content. Due to this, the analysis is prescribed during mass preventive examinations, during initial visits of patients to doctors, upon admission to the hospital. The results are used to assess the general condition, diagnose diseases, and evaluate the effectiveness of therapeutic measures. With the final data of the study, it is worth contacting your doctor. Most often they are a therapist, pediatrician, nephrologist or urologist.