Epithelial cells in urine are generally of little specific diagnostic utility. Cells lining the urinary tract at any level may slough into the urine. In the case of voided samples, even cells from the genital tract can appear in the sample. Most commonly seen are non-keratinized squamous epithelial cells from the distal urethra, prepuce and/or vagina, keratinized squamous cells from the skin or vulva (upper panel at right), and transitional epithelial cells from the bladder and urethra (lower panel). Small transitional epithelial cells can be very difficult to distinguish from WBCs, because they have the same granular appearance. In general, transitional epithelial cells have more irregular borders than WBCs (which are uniformly more round). When we are unsure about the origin of the cells in urine, we can stain a urine sediment with Wright's stain (or Diff-quik) and perform a cytologic examination on the urine sediment. More information on epithelial cells in urine is in the Urine Sediment Atlas.