Urine sediment

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The urine sediment or urine sediment (Latin sedimentum : sediment) is a preparation of the urine for the microscopic assessment of the solid components. If certain insoluble constituents are found in the urine sediment, this can be an indication of certain diseases of the kidneys or the urinary organs (ureter, urinary bladder). The examination of the urine sediment is easy to carry out and, as a diagnostic method, provides important orientational information within the framework of a microbiological assessment or the so-called urine status within the framework of a urine examination .
A distinction is made between organized urine sediment (urine cylinders , epithelial cells , leukocytes , erythrocytes , bacteria ) and so-called non-organized urine sediments (crystals).

Standardized implementation

A standardized method is used to precisely quantify the constituents of the urine sediment. For this purpose, 10 ml urine are centrifuged for 5 minutes at 500  g , then 9.5 ml of the supernatant are discarded and the sediment is taken up in the remaining 0.5 ml. A drop of it is placed on a slide for examination. For viewing without further preparation, the drop is covered untreated and viewed in a microscope using phase contrast . The cells in the sediment are quantified in a counting chamber . Usually, the urine sediment is also stained after it has dried on the slide in order to e.g. B. to better assess cells or bacteria. The staining method used is Giemsa staining for cells and Gram staining for bacteria.

Microbiological and cytological assessment

The detection of bacteria alone does not prove an infection of the kidney or urinary organs. The bacteria can after removal of the urine have been introduced, have increased due to inappropriate storage or transport or improper urine collection (no mid-stream urine ) of the normal bacterial colonization of the anterior urethra originate. In addition to the quantification of the bacteria (germs per ml urine), the detection of leukocytes, especially neutrophilic granulocytes ("pus cells") in the urine sediment proves an infection.

If numerous epithelial cells (especially squamous cells) of the urethra are found in the urine sediment, it can be assumed that the urine was taken improperly and further bacteriological examinations are usually not useful.

Many red blood cells (erythrocytes) in the sediment indicate possible bleeding and inflammation of the urinary bladder ( cystitis ) or the prostate ( prostatitis ). This so-called hematuria can also be found in tuberculosis or schistosomiasis .

With normal Giemsa staining one can already recognize bacteria and differentiate them based on their shape. In the event of an infection, differentiating between cocci (mostly enterococci ), diplococci (mostly Neisseria gonorrhoeae ) or rod bacteria (mostly E. coli ) provides initial information about the pathogen, which can quickly be further differentiated with a Gram stain for appropriate first therapy to select. In the case of a complicated or chronically recurrent infection, it is necessary to cultivate the pathogen. If numerous leukocytes are found in the urine sediment, but no bacteria, an examination for chlamydia is recommended.

In addition to bacteria, parasites or parasite eggs can also be detected in the urine sediment (e.g. oxyurs , pair leeches , trichomonads ).

Urine cylinders

In the presence of the Tamm-Horsfall protein , accumulations of cells, cellular fragments or organic substances (lipids, proteins, hemoglobin ) form around it as a sticky matrix . These form elongated structures known as urine cylinders or "cylinders" for short. In particular, protein cylinders indicate a pathological process in kidney tissue. Cylinders made of bacteria or granulocytes indicate a purulent inflammation of the renal pelvis ( pyelonephritis ).

Crystals

Leaving urine to stand increases the pH through the bacterial conversion of urea to ammonia . The ions and molecules dissolved in the urine form crystals , depending on their concentration, the presence of urinary colloids and the pH value , which can be detected in the urine sediment. Viewing under a polarizing microscope allows you to distinguish between the different crystals. The most commonly observed crystals consist of:

swell

  • Lothar Thomas: Labor und Diagnose , 6th Edition, Frankfurt 2005, pp. 553-560 ISBN 3-9805215-5-9

literature

  • Sabine Althof, Joachim Kindler: The urine sediment: Atlas - investigation technique - assessment . Georg Thieme Verlag, 2005 excerpts from Google Books
  • E. Mustard: microscopic examination of urine sediments. 2nd Edition. Leipzig 1909.

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