Preparation of urine and urinary sediment

Aspect

Freshly voided urine is usually clear. The terms to describe the appearance of urine are: clear, slightly cloudy, cloudy, flaky, and turbid. A turbid specimen should be clarified before microscopic examination.

Material

Standardization of the examination of the urinary sediment is recommended.
The plastic tubes used for centrifugation should allow macroscopic observation and should be strong enough not to break during centrifugation.
10 ml of urine are sufficient for chemical analysis and microscopic examination. 12 mL graduated tubes with a conical bottom (to concentrate the sediment) should be used. Smaller volumes are used for children.

Procedure

Before chemical analysis (test strips), the samples must be clear and well mixed and the volume carefully measured. Centrifuge 10 ml of urine for 5 minutes at 400 g. Decant the supernatant leaving only 0.5 mL at the bottom of the tube.

20 µL of the staining solution of Sternheimer-Malbin can be added and mixed with 0.5 mL of concentrated sediment. Drop 10 µL of the colored or uncolored suspension on a glass slide and cover with a cover slip. An exact concentration factor is crucial for a valid correlation to the urinary volume. The concentration factor between the initial volume and/or the supernatant is approximately 10 to 25. 20 µL

Next, proceed to the  microscopic examination of the sediment