Urine examination

Urine is an easily available biological fluid, which provides valuable information about the state of the organism and its metabolism. Urine examination is one of the basic clinical and biochemical procedures that significantly contribute to the diagnosis, monitoring of the disease and treatment results. Urine analysis uses a range of methods, from the simplest color and clotting tube reactions to sophisticated and automated methods such as flow cytometry or immunochemical analysis. Thanks to diagnostic strips, basic examinations can be performed not only in the laboratory, but directly in surgeries or at the patient's bedside.

Urine collection
An important prerequisite for valid urine analysis results is the correct procedure for its collection and collection.

First morning urine
The first morning urine is best for most urine tests. It is recommended that urine collection be preceded by a supine position of at least eight hours. Morning urine is more concentrated and acidic. It is especially suitable for chemical examination of urine. Urine collected later is already affected by fluid intake, food and exercise.

Urine is usually obtained by spontaneous micturition. The actual urine collection is performed after thorough washing and drying of the external urethral orifice. Urine in a clean, dry, closable container that contains no detergent or disinfectant residues that distort the results of the chemical analysis. The middle urine flow is intended for examination. The first stream is always contaminated with cells and bacteria from around the outer urethra. Therefore, the patient urinates the first portion of urine into the toilet and captures the second stream of urine in the collection container, in which the analysis is performed.

In certain situations, urine is collected by suprapubic bladder puncture (if we want so-called sterile collection) or by bladder catheterization.

In women, we avoid examinations in the period just before menstruation until the end of menstruation. Stabilizing additives are not required for most qualitative and semi-quantitative chemical analyzes of urine by test strips. If it is not possible to perform the examination within 2 hours after collection, it is advisable to store the urine in a refrigerator or preserve it.

With prolonged storage, the composition of the urine changes.

Second morning urine
The sample is soaked 2-4 hours after the first urination. Its composition is already affected by food and fluid intake and exercise. The second morning urine is recommended mainly for quantitative determinations related to the concentration of creatinine in the urine.

Random urine sample
A random urine sample is a label for fresh urine collection without knowledge of collection time and volume, details of patient preparation are not usually known. It is possible for acute conditions. Urine analysis can be fraught with a number of errors.

Time urine collection
For quantitative analyzes and to determine the clearance of different analytes, urine should be collected at intervals. Short-term urine collection lasts 1-3 hours, long-term 12-24 hours. Urine is sometimes collected overnight (for 8 hours), eg to determine albuminuria. The accuracy of the collection is very important for the test results. The accuracy of urine collection can be roughly checked by determining the creatinine concentration in the urine.

Urine is collected in well-cleaned containers stored in a cool, dark place, or with the addition of a preservative.

Collection can be started at any time during the day by emptying the bladder and recording the time. However, with a 24-hour collection, the best time in the morning is between 6 and 7 o'clock. At the beginning of the urine collection, the patient must urinate; this portion is not yet collected. From that moment on, all the urine is collected. The patient should be instructed to urinate in the collection container before going on the stool. Urine collection is completed in exactly 24 hours by urinating the entire contents of the bladder into a collection container.

Urine volume is measured at the end of the urine collection, the urine is mixed thoroughly, and at least 5 ml of an average sample is usually delivered to the laboratory with the exact time of the start and end of the collection (to the nearest minute) and the exact volume of urine collected.

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