Introduction

To identify urinary sediment cells is a difficult task. Some cells have characteristic features, therefore easily identifiable. On the other hand, some cells, even with sophisticated stains, remain a challenge. The diversity of cells that one can meet is notable. Cells found in urine can belong to the reticuloendothelial system (leucocyte, macrophage) or to the epithelial system. Urinary cells can originate from the kidney or from the lower urinary tract, from the superficial lining or from a deeper source. In an adult male, cells can also originate from the prostate and the urethra.

Urine is not a favorable media for maintaining cell structures. Most cells undergo rapid changes (degeneration, rupture, vacuolization, granulation of the cytoplasm) that profoundly affect the visual aspect of the cell. These changes are more pronounced if the cell comes from the higher urinary tract because agression due to osmotic variation adds to the energy lack and other causes of morphological change. The best preserved cells are usually bladder cells, while a well preserved proximal renal tubular cell is exceptional. Some pathologies, like inflammation, metaplasia, neoplasia, are known to affect the cellular aspect.

All experienced urinary sediment microscopists have seen some cases of cells, so special, that identification was a best guess based on the sediments context. This situation, while being frustrating, should not be considered as a failure. Identification of all the figures seen in the urinary sediment is quite impossible; so,one must focus his effort on element of clinical value.