What does the presence of few bacteria and epithelial cells in the urinalysis indicate?

Interpretation of Few Bacteria and Epithelial Cells in Urinalysis

The presence of few bacteria and epithelial cells in urinalysis most likely represents contamination rather than a true urinary tract infection (UTI), especially when not accompanied by significant pyuria. 1, 2

Understanding Urinalysis Components

• Epithelial cells in urine samples typically indicate contamination from the urethra or external genitalia during collection, as they are not normally present in properly collected specimens 1
• The presence of bacteria without significant pyuria (white blood cells) is usually attributable to external contamination, asymptomatic bacteriuria, or rarely, very early infection before inflammation begins 1
• According to the American Academy of Pediatrics guidelines, true UTI requires both bacteriuria and pyuria, as pyuria represents the host's inflammatory response 1

Diagnostic Thresholds for UTI

• For a diagnosis of UTI, clinicians should look for:
  • Significant bacteriuria (≥50,000 CFU/mL of a single uropathogen) 1, 3
  • Evidence of pyuria (≥10 WBCs/mm³ on enhanced urinalysis or ≥5 WBCs/HPF on centrifuged specimen) 1
  • Positive leukocyte esterase and/or nitrite test 1
• Low bacterial counts with few epithelial cells but without significant pyuria fall below diagnostic thresholds for UTI 3, 2

Collection Method Considerations

• The method of urine collection significantly impacts interpretation:
  • Bag-collected specimens have high contamination rates (12-83%) 1
  • Clean-catch specimens have contamination rates of 0-29% 1
  • Catheterization or suprapubic aspiration provide the most reliable specimens 1
• Specimens with epithelial cells are more likely to represent contamination, especially when obtained via non-invasive collection methods 1

Clinical Decision Making

• When few bacteria and epithelial cells are present without significant pyuria:
  • This likely represents contamination rather than infection 1, 2
  • No treatment is typically required in asymptomatic individuals 2
  • Consider repeat specimen collection using a more reliable method if symptoms suggest UTI 1, 2

Special Considerations

• In symptomatic patients with dysuria, frequency, or urgency despite negative urinalysis:
  • Consider repeat testing with proper collection technique 2, 4
  • Evaluate for other causes of urinary symptoms 2
• In febrile infants, the presence of both bacteriuria and pyuria is required for UTI diagnosis, as asymptomatic bacteriuria can occur in 0.7% of afebrile girls 1
• Bacteria can occasionally adhere to bladder epithelium without causing significant pyuria, potentially explaining some recurrent UTI symptoms with negative cultures 5, 6

Common Pitfalls to Avoid

• Treating based on the presence of bacteria alone without considering pyuria can lead to unnecessary antibiotic use 1, 2
• Ignoring specimen quality markers (epithelial cells) may result in overdiagnosis of UTI 2
• Failing to recognize that multiple organisms typically indicate contamination rather than infection 3, 2
• Delaying specimen processing can lead to falsely elevated bacterial counts due to bacterial growth at room temperature 3