Urinalysis

With the urine, the body gets rid of excess substances such as metabolic waste, drugs and toxins. The urine is also part of a regulatory mechanism that balances fluid and electrolytes. His analysis may give indications of various disorders.

Composition of urine

The urine consists to 95% of water, it also contains metabolic (end) products such as urea, uric acid and creatinine, salts, acids, dyes, hormones and water-soluble vitamins. Urine is produced in the two kidneys, collected in the appropriate renal pelvis, and enters the urinary bladder via the two ureters. Urgency arises as soon as a certain filling state is reached there; urethral emptying can be controlled at will.

The quality of the urine and the frequency of bladder emptying depend in healthy people on the amount of fluid absorbed and lost through the skin and respiration. The kidneys initially produce about 150 liters of urine per day and ultimately reduce this amount to 1.5-2 liters, which are excreted.

The typical urinary odor is caused by uric acid and ammonia. The latter is increasingly formed when urine is longer and is responsible for the then pungent odor. The color of the urine is preserved by bile pigments, which are produced by the breakdown of the red blood cells. It varies from light to dark yellow depending on the degree of dilution.

Changes in the urine: causes

One or more of the factors described above can be altered by morbid processes such as bladder infections and kidney disease, thus helping with diagnostics. In addition, it can be searched for blood, cells, pathogens and other admixtures. In certain metabolic disorders, enzymes and hormones can be measured, in case of disorders of the kidney or bladder function, special tests can follow.

The following are typical causes for changes in urine color, amount of urine and odor:

  • Color: Certain foods such as blackberries (reddish brown) and rhubarb (lemon yellow) or medications such as antibiotics (brown) and vitamin tablets (orange) cause temporary discoloration. In case of diseases or injuries of the kidneys or urinary tract, protein, red and white blood cells or bacteria may cause turbidity or reddening. Also liver inflammation and transfusion incidents or porphyria can cause a red coloration of the urine. The Alkaptonurie, a rare metabolic disease colors the urine brown-black, in liver inflammation, it can also be dark brown to greenish and have yellow foam on shaking.
  • Quantity and odor: In renal function disorders, urine production may be limited; certain metabolic diseases, such as diabetes or medications, increase urine output and very light urine. Changes in the odor may be caused by food - after consumption of asparagus occurs in about half of people a typical smell. Strongly-smelling urine is the result of a bacterial infection, a foul smell can be caused by bladder tumors. Typical is a sour, acetone-like odor in diabetes if it is not well adjusted.

Gaining a urine sample

In general, the sample is obtained from the midstream urine, the middle urine portion of about 20-40 ml, which - without interrupting the stream of urine - is collected after the first portion has been emptied into the toilet. This is to ensure that possibly contained germs do not originate from the external genitalia, but from the urinary tract. In order to reduce the risk of contamination of the sample and thus to ensure the validity of the analysis, the person concerned should pay attention to the following points:

  • The urine must be collected in a closable, clean urine cup. Doctor or pharmacist provide this.
  • The genitals must be washed carefully before.
  • When urinating, the woman should spread her labia, the man retract his foreskin.

If in special cases the urine must be safely sterile, it can also be obtained by the doctor by means of a catheter or a direct puncture of the bladder through the abdominal wall.

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