Can a child have a urinary tract infection (UTI) if the urine routine shows no bacteria but pus cells are present?

Can a Child Have a UTI with Pus Cells Present but No Bacteria on Urinalysis?

Yes, a child can have a UTI even when bacteria are not visible on urinalysis but pus cells are present, though this scenario requires careful interpretation and should prompt urine culture to establish the diagnosis. 1, 2

Diagnostic Requirements for UTI

The American Academy of Pediatrics establishes that both urinalysis suggesting infection (pyuria and/or bacteriuria) AND a positive urine culture with ≥50,000 CFU/mL are required to confirm UTI in febrile infants and children. 1, 2

Key Principle: Neither Finding Alone is Sufficient

• Pyuria without bacteriuria is insufficient to diagnose UTI because it is nonspecific and occurs in non-infectious conditions such as Kawasaki disease, chemical urethritis, or streptococcal infections. 1
• Bacteriuria without pyuria typically represents external contamination or asymptomatic bacteriuria rather than true infection. 1, 2
• The presence of both findings together signals true UTI, as the host inflammatory response (pyuria) is what causes renal scarring, not just the presence of organisms. 1

Why Bacteria May Not Be Visible Despite Infection

Several important scenarios explain absent bacteria on urinalysis with pyuria present:

• Early infection stage: Very early UTI may show pyuria before significant bacteriuria develops. 1
• Non-E. coli pathogens: Organisms like Klebsiella and Enterococcus are less frequently associated with visible bacteriuria but still cause true infection with pyuria. 1, 3
• Specimen timing: Fresh urine (<1 hour) is essential for accurate microscopy; delayed processing reduces bacterial visibility. 1
• Low bacterial counts: Some true UTIs present with colony counts between 10,000-50,000 CFU/mL, which may not show bacteria on microscopy but still represent infection. 1

Clinical Action When Pus Cells Present Without Bacteria

If urinalysis shows pyuria (10 pus cells in this case) without visible bacteria, you must obtain a properly collected urine culture via catheterization or suprapubic aspiration. 1, 2

Critical Collection Method Considerations

• Bag-collected specimens cannot establish UTI diagnosis even with positive culture, due to high contamination rates from perineal skin, vaginal secretions in girls, or prepuce in uncircumcised boys. 1, 2
• A positive culture from bag collection requires confirmation via catheterization or suprapubic aspiration. 1, 2
• For catheterization, discard the first few milliliters to reduce urethral flora contamination. 1, 2

Organism-Specific Patterns

Research demonstrates that pyuria may be absent or minimal in UTIs caused by certain pathogens:

• E. coli causes pyuria in 80.6% of cases. 3
• Klebsiella species cause pyuria in only 53.3% of cases. 3
• Enterococcus species cause pyuria in only 52.0% of cases. 3

This means the reverse is also true: when pyuria is present, culture is essential to identify the causative organism, as bacteria may not be microscopically visible with all uropathogens. 3

Common Pitfalls to Avoid

• Do not rely on urinalysis alone without culture confirmation—this leads to both overdiagnosis and missed infections. 2, 4
• Do not dismiss the possibility of UTI based solely on absent bacteria if pyuria is present and clinical symptoms suggest infection. 3
• Do not use bag-collected specimens for definitive diagnosis; they are only suitable for screening. 1
• Do not delay culture in symptomatic children with pyuria, even without visible bacteria. 3

Bottom Line for This Case

In a child with 10 pus cells and no bacteria visible on routine urinalysis:

1. UTI remains possible and cannot be excluded. 1, 3
2. Obtain urine culture via catheterization (not bag collection) to establish or exclude the diagnosis. 1, 2
3. Consider clinical context: fever, symptoms, and risk factors guide urgency of evaluation. 1
4. Await culture results before making treatment decisions, as pyuria alone does not confirm infection. 1, 2

The culture result showing ≥50,000 CFU/mL of a uropathogen combined with the pyuria would confirm UTI, while negative culture would suggest an alternative cause for the pyuria. 1, 5, 2