Microscopy Solutions for Urinalysis

Urine is a key indicator for many diseases such as urinary tract infections, kidney disease and
diabetes. And, normally it’s easy to obtain. That’s why, the examination of urine is part of each clinical laboratory routine to analyze whether there are abnormalities.

After a visual analysis of color, smell and appearance of a fresh urine sample, usually a chemical analysis is performed using so called dipsticks. In case of abnormal findings on the visual or chemical analysis, a microscopic analysis is typically performed on urine sediment to visualize solid components such as blood cells, epithelial cells, microorganisms and pathogens.

Urine sediment is normally examined with a transmitted light microscope with brightfield or phase contrast. To visualize crystals, polarization contrast can be helpful, too. The sediment is first examined with low magnification to identify most crystals, casts, squamous cells, and other large objects. Next, examination is carried out at high magnification to identify crystals, cells, and bacteria.
 

Urine is traditionally examined with upright light microscopes. In general, brightfield microscopes are the instrument of choice. However, urinalysis guidelines also recommend the use of microscopes equipped with phase contrast and polarized light filters to identify urine particles like dysmorphic erythrocytes and casts (phase contrast) as well as lipids and crystals (polarized light). LED illumination increases the quality of sample visualization. Standard objectives for routine urinary sediment are a 10x for casts and a 40x for cells and other smaller structures, resulting in a 100x or 400x magnification (when used with 10x eyepieces). 400x is also fine to visualize bacteria. In order to get a more detailed observation of bacterial morphology, such as shape, size, and cellular structures, 1000x magnification can be helpful. However, at a higher magnification, it can be increasingly difficult to keep them in focus as they move.