Urinalysis (urinalysis): examination procedure

Various methods are available for examining urine. Test strips are a quick form of urine testing. Other investigations require laboratory analysis of the urine. Sometimes, a urine culture needs to be done. There are also different functional tests for urine testing. In the following, we present the various examination methods.

Urine Strip Rapid Test

The dipstick urine test is a quick, easy-to-perform test that uses a chemical reaction. This allows the most essential substances in the urine to be detected:

• white blood cells (leukocytes): in case of inflammation
• Protein: Diabetes, inflammation or other damage to the kidneys (e.g. from medication or high blood pressure ), tumours
• Blood: Inflammation or injury to the kidneys or urinary tract, tumours
• Glucose, Ketones: Diabetes
• Nitrite: sign of urinary tract infection
• pH value:  This can be used to determine the acidity. Its fluctuations can be caused by diet but also by metabolic disorders or cancer.

The finger-length test strip is briefly dipped into the urine so that all test fields are wet. These are coated with different substances that react with the urine and change their colour. The discolouration is compared with a particular colour scale after waiting 1 to 2 minutes. The urine strip rapid test is also part of the check-ups during pregnancy.

Urine test by laboratory diagnosis

Further analysis in the laboratory is carried out depending on the findings and the suspected diagnosis. Other tests, such as blood tests or ultrasounds, are usually carried out simultaneously, sometimes also tests to assess kidney and bladder function.

On the one hand, the urine sample is looked at under the microscope; on the other hand, the presence and amount of certain substances can be determined. If there is a suspicion of an infection of the kidney or bladder, a “urine culture” can be created.

• Admixtures under the microscope: After centrifugation, the solid components accumulate (urine sediment) and can be examined under a microscope. Scattered tissue cells from the mucous membrane of the urinary tract and a few white and red blood cells or mucous threads are not of concern. However, if more significant amounts of protein cylinders, urine crystals, pus or pathogens are found, there is a suspicion of a disease of the kidneys or the urinary tract. Abnormal cells, for example, from a malignant tumour, can also be identified under the microscope (cytological examination).
• Urine culture: A coated slide is dipped in the fresh urine, placed in an associated container, and sent to the microbiology laboratory. If germs are included, bacterial colonies appear about 24 hours later; their number is estimated using a comparison table. In the next step, the pathogens can be precisely identified, and it can be determined which antibiotics are effective. Germs are not only found in an infection of the kidneys or urinary tract but can also indicate a tumour.
• Urine analysis for certain substances:  Water-soluble substances are usually excreted in the urine. For example, electrolytes (such as  sodium ,  potassium , calcium), drug active ingredients, poisons, doping agents or hormones and their breakdown products can be determined in the urine. Their quantity then allows conclusions to be drawn about an enzyme defect (for example porphyria) or a hormonal disorder.

Urinalysis through functional tests

If there is a suspicion that kidney or bladder function is impaired, a number of special tests are available.

• 24-hour urine collection:  The patient collects all the urine that he or she passes over 24 hours in a special collection container. This can then  be used to determine creatinine  , a substance that allows conclusions to be drawn about the functioning of the kidneys.
• Specific gravity of urine:  This involves using a specific measuring cylinder to determine the mass of urine per unit volume, which depends on the amount of substances dissolved in the urine. Deviations from the normal value are often signs of kidney failure.
• Urodynamics: This generic term includes a series of examinations that can be used to check bladder functions. They are used, for example, when patients cannot hold their water ( urinary incontinence ). Among other things, the amount of urine that flows through the bladder within a certain period, the pressure in the bladder and whether there is still urine in it after emptying are determined.