What's the next step for a patient with a urine culture showing only leukocytes (white blood cells), indicating a possible non-bacterial cause of symptoms or viral infection?

Management of Urine Culture Positive Only for Leukocytes

Do not treat with antibiotics unless the patient has specific urinary symptoms (dysuria, frequency, urgency, fever, or gross hematuria), as leukocytes alone represent pyuria without confirmed bacterial infection and likely indicates either asymptomatic bacteriuria, contamination, or a non-bacterial cause. 1, 2

Immediate Clinical Assessment

The critical first step is determining whether specific urinary symptoms are present:

• Look for dysuria, urinary frequency, urgency, fever >38°C, gross hematuria, or new/worsening urinary incontinence 3, 2
• Non-specific symptoms like confusion, functional decline, or malaise alone should NOT trigger UTI treatment, especially in elderly patients 1, 2
• If the patient is asymptomatic, stop here—no further testing or treatment is indicated 3, 1

Understanding Your Result

A urine culture showing "only leukocytes" (pyuria without bacterial growth) has several possible explanations:

• Specimen contamination is the most common cause, particularly with high epithelial cell counts 2
• Asymptomatic bacteriuria with pyuria occurs in 10-50% of elderly populations and does not require treatment 1, 4
• Partially treated infection if antibiotics were recently given 4
• Non-bacterial causes including sexually transmitted infections, tuberculosis, fungal infection, urolithiasis, or interstitial cystitis 4

The absence of bacterial growth on standard culture effectively rules out typical bacterial UTI with >95% specificity 2

Management Algorithm

If Patient is Asymptomatic:

• Do not order additional cultures or initiate antibiotics 3, 1
• Asymptomatic bacteriuria with pyuria should never be treated (Grade A-I recommendation from IDSA) 3, 4
• Studies demonstrate that untreated asymptomatic bacteriuria persists 1-2 years without increased morbidity or mortality 1

If Patient Has Specific Urinary Symptoms:

1. Obtain a properly collected specimen using midstream clean-catch (cooperative patients) or in-and-out catheterization (women unable to provide clean specimens) 3, 2
2. Repeat urinalysis with microscopy to confirm pyuria (≥10 WBCs/high-power field) and check for nitrites 3, 2
3. Send urine culture with antimicrobial susceptibility testing before starting any antibiotics 2, 4
4. Consider non-bacterial causes if culture remains negative after 48 hours with persistent symptoms 4

Special Considerations for Non-Bacterial Causes:

If symptoms persist with sterile pyuria (negative culture with confirmed pyuria):

• Test for sexually transmitted infections (chlamydia, gonorrhea) in sexually active patients 4
• Consider tuberculosis testing in high-risk populations 4
• Order renal/bladder ultrasound to evaluate for stones or anatomic abnormalities 4
• Evaluate for interstitial cystitis in patients with chronic symptoms 4

When to Consider Empiric Antibiotics

Hold empiric antibiotics until a specific pathogen is identified unless the patient has: 4

• Signs of systemic infection/urosepsis (fever >38.3°C, rigors, hypotension, hemodynamic instability) 2, 4
• Suspected pyelonephritis with flank pain and high fever 4
• Immunocompromised status with concerning symptoms 4

Even in these scenarios, always obtain culture before starting antibiotics 2, 4

Critical Pitfalls to Avoid

• Do not treat based on cloudy or malodorous urine alone—these observations do not indicate infection in elderly patients 4
• Do not assume confusion or delirium in elderly patients indicates UTI without specific urinary symptoms 1, 2
• Do not continue antibiotics if started empirically once culture returns negative—this provides no benefit and promotes resistance 2
• Do not dismiss this as "just asymptomatic bacteriuria" if symptoms are present—the presence of symptoms with pyuria indicates true inflammation requiring investigation 4

Special Population Considerations

Catheterized Patients:

• Pyuria and bacteriuria are nearly universal in chronic catheterization and should not be treated if asymptomatic 1, 2
• Change long-term catheters before collecting specimens if urosepsis is suspected 3, 4

Elderly/Long-Term Care Residents:

• Evaluate only with acute onset of specific UTI-associated symptoms 3, 2
• The presence of pyuria has extremely low predictive value due to 10-50% prevalence of asymptomatic bacteriuria 1, 2

Febrile Infants:

• Always obtain both urinalysis and culture before antibiotics, as 10-50% of UTIs have false-negative urinalysis 2

The Bottom Line

Research demonstrates that 64% of hospitalized patients with asymptomatic bacteriuria receive inappropriate antimicrobial therapy, accounting for substantial unnecessary antibiotic use 5. Your result of leukocytes without bacterial growth does not justify antibiotic treatment unless accompanied by specific urinary symptoms. If symptoms are present, proper specimen collection and culture are essential before treatment decisions. If symptoms persist with negative cultures, investigate non-bacterial causes rather than empirically treating with standard UTI antibiotics.