The urinary sediment was introduced into clinical practice in the late 1830s in Paris at La Charité hospital by François Rayer and his pupil Eugène Napoléon Vigla. By the end of the 19th century, all the main particles had been identified and the main urine profiles had been described. However, in the subsequent century, the 20th century, the urinary sediment examination knew only a progressive decline with only very few exceptions. One was the original and important work of Thomas Addis in the 1920s and the other was the publication, in 1982, of a paper by Fairley and Birch on the utility of urinary erythrocyte morphology evaluation by phase contrast microscopy in patients with hematuria.
Methodological aspects are very important for urine sediment. The main methodological aspects include: a correct urine collection; a standardised method for the handling of the urine; the use of a proper microscope and the use of a proper report to describe the findings.
Collection of the urine:-
According to the strategy of the single lab, we can ask the patient to supply the first or the second urine of the morning. Usually ask for the second urine, since overnight urine, due to its prolonged permanence in the bladder can favour the lysis of particles. Advise the patient to avoid strenuous physical effort in the hours preceding the test, since this may influence in various ways the findings (for instance by causing haematuria and/or cylindruria). Also advise the patient to clean the external genitalia in an ordinary way. In order to avoid contamination, the male has to uncover the glans and female to spread the labia of the vagina. For the same reason, collect midstream urine. It’s important to remember that urine collection during menstruation must be avoided because of the high probability of blood contamination. It is also important to use a proper urine container (with a capacity of at least 50 to 100 mL, an opening of at least of 5 cm to allow easy collection of urine for both men and women, a wide base to avoid accidental spillage, a cap to avoid leakage, a label for patient identification).
Standarized method for handling of urine sample:-
What about a standardized method for the handling of urine? Why is standardization of the handling of the urine important? It is important because only with a standardized method we can obtain quantitative reproducible results. Ask the patient to supply the second urine of the morning produced over a period of 2 hours; then, centrifuge a 10 mL aliquot of urine for 10 minutes at 400 G , which correspond to 2,000rpm . Then, remove with a pump a fixed volume of supernatant urine, which is 9.5 mL. Then, with a Pasteur pipette, gently but thoroughly re-suspend the sediment in the remaining 0.5 mL of urine. Then, with a precision pipette, transfer 50 mL of resuspended urine to a glass slide, which is covered with a coverslip of a fixed surface, namely 32 x 24 mm . Then, examine the samples at low and high magnification (160x and 400x) within 3 hours from urine collection. For routine practice, express the particles as lowest/highest number seen by microscopic field.
Various findings on urine microscopy:-
To know how the various Casts and Crystals appear on microscopy, download the file showing the pictures of common findings of urine microscopy. Click the link below to download the file.
