Epithelium is a layer of cells lining the cavities and surfaces of blood vessels and organs throughout the body, including mucous membranes and the urogenital tract. There are 3 types of epithelial cells that can be found in the urinary sediment: squamous epithelial cells, transitional epithelial cells and renal epithelial cells.
Urine runs through the kidneys, ureters and other elements of the urinary system, being always in contact with the epithelium. Occasionally, epithelial cells come off and can be detected by a microscopic analysis of the urinal sediment. Since the shape of epithelial cells is different in different organs, different types of epithelial cells can be detected in the urine.
Squamous Epithelial Cells. In men, squamous epithelial cells get into the urine from the lower third of the urethra and are almost never found in the urine of healthy individuals. As for women, squamous epithelial cells get into the urine from their urethra and vagina, so they are almost always found in their urine.
Squamous epithelial cells have no significant diagnostic value. It is common to find occasional epithelial cells in urine during pregnancy. However, high levels of squamous epithelial cells may also be due to urinary tract infections.
Transitional Epithelial Cells line renal pelvises, ureters, bladder, gland ducts of the prostate, and the upper part of the urethra. Single transitional epithelial cells may be found in the urine of healthy individuals.
High concentrations of transitional epithelial cells may occur due to inflammatory diseases of the urinary system.
Renal Epithelial Cells. The presence of renal cells in the urine is a sign of renal parenchyma disorders. Renal cells are not detected in the urine of healthy individuals. Single renal cells may be found in the urine of newborn babies.