Squamous Cells in Urinalysis

Origin and Normal Occurrence

• Squamous epithelial cells normally line the distal urethra and the trigone area of the bladder, as well as the cervicovaginal region in women 1
• The distal third of the urethra is dominated by squamous epithelium, while the proximal two-thirds contains transitional epithelium 2, 3

Clinical Significance and Interpretation

• A significant number of squamous epithelial cells alongside >10 WBCs suggests potential sample contamination 1

Collection Method Considerations

• Collection method significantly affects contamination rates: Clean-catch specimens have a 27% contamination rate, Bag specimens have a 65-68% contamination rate, and Catheterized specimens have only a 4.7% contamination rate 1
• Proper cleansing of the perineal area before collection can reduce contamination rates from 23.9% to 7.8% 1

Recommendations for Practice

• When significant squamous epithelial cells are present alongside mixed bacterial flora, consider recollection using a more reliable method if clinical suspicion for UTI remains high 1
• Catheterization provides more reliable specimens with higher sensitivity (95%) and specificity (99%) 1
• The Bethesda System should be used for reporting urine cytology results, with appropriate follow-up for any epithelial cell abnormalities 4, 5

Special Considerations

• In HIV-infected women, more frequent cervical screening may be needed due to higher risk of squamous intraepithelial lesions 4, 5, 6
• In patients with neurogenic lower urinary tract dysfunction, the presence of squamous cells alongside hematuria may warrant cystoscopic evaluation 7