From the Guidelines
The presence of epithelial cells in urine is a significant indicator of urinary tract health, and their interpretation should be considered in the context of other urinalysis findings, such as protein, blood, or bacteria in the urine, as suggested by recent studies 1. When evaluating the significance of epithelial cells in urine, it is essential to consider the type and quantity of cells present.
- Urine normally contains a few squamous epithelial cells from the urethra, which are shed during normal cell turnover.
- However, increased numbers of epithelial cells may indicate inflammation or infection in the urinary tract.
- Specifically, finding renal tubular epithelial cells suggests kidney damage, while transitional epithelial cells may indicate bladder or ureter inflammation. The underlying mechanism involves damaged or inflamed tissues shedding more cells than usual into the urine, and recent research has highlighted the importance of extracellular vesicles (EVs) in understanding kidney diseases and their potential use as biomarkers and therapeutic agents 1. According to a recent study published in Kidney International, EVs derived from epithelial cell culture models of the nephron depicted similar EV signatures to uEVs of healthy donors, suggesting that the epithelial cells directly in contact with the primary urine contribute the majority of uEVs 1. In clinical practice, the presence of epithelial cells in urine should be interpreted with caution, considering the potential for contamination during collection, and the need for additional testing or monitoring depending on symptoms and other urinary findings, as emphasized by the Minimal Information for Studies of Extracellular Vesicles (MISEV) 2023 guidelines 1.
From the Research
Significance of Epithelial Cells in Urine
- Epithelial cells in urine can be used as models for genetic kidney diseases, particularly podocytes and proximal tubular epithelial cells (PTECs) 2
- The presence of renal epithelial cells in urine sediment can be a valuable noninvasive method to get information about disease activity or disease type, and can be used as a follow-up after a biopsy in an outpatient setting 3
- Urinary renal tubular epithelial cells and casts can be predictors of renal outcomes in patients with biopsy-proven diabetic nephropathy, with their presence being associated with more severe kidney injury and worse renal outcomes 4
Clinical Relevance of Epithelial Cells
- The correct identification of epithelial cell subtypes, particularly renal tubular epithelial cells (RTECs), can be useful for clinical diagnosis and treatment 5
- Podocalyxin-positive glomerular epithelial cells in urine have been found to correlate with a positive outcome in FSGS patients, suggesting a potential prognostic value for proteinuria development and kidney function 6
Diagnostic and Prognostic Value
- Epithelial cells in urine can provide valuable information about kidney disease activity and type, and can be used to monitor disease progression and response to treatment 3, 4, 6
- The presence of specific epithelial cell types, such as podocytes and PTECs, can be used to diagnose and monitor genetic kidney diseases 2