What is the appropriate diagnosis and treatment for a child with leukocytes (white blood cells) in their urine?

Diagnosis and Management of Leukocyturia in Children

A child with leukocytes in the urine requires immediate evaluation for urinary tract infection through proper urine collection (catheterization or suprapubic aspiration in non-toilet-trained children), urinalysis, and urine culture before initiating antibiotics. 1

Diagnostic Approach

Initial Assessment

The presence of leukocytes alone is insufficient to diagnose UTI—you must assess for accompanying symptoms:

• Fever without obvious source (especially in children 2-24 months) 2
• Dysuria, frequency, or urgency (in older children) 1
• Gross hematuria 1
• Irritability or poor feeding (in infants) 3

Critical point: Leukocytes can indicate inflammation from many non-infectious causes, so clinical correlation is essential. 1

Proper Specimen Collection

For non-toilet-trained children:

• Use catheterization or suprapubic aspiration—these have low contamination rates and confirm UTI 4
• Never rely on bag-collected specimens for diagnosis—they have only 15% positive predictive value and require catheterized confirmation 1, 5

For toilet-trained children:

• Clean-catch midstream urine after cleaning external genitalia has good diagnostic accuracy 4

Urinalysis Interpretation

Leukocyte esterase testing:

• Sensitivity: 84% in children 2
• Specificity: 91% 2
• When combined with nitrite testing, sensitivity increases to 93% with 96% specificity 1

Key interpretation points:

• Positive leukocyte esterase + symptoms = proceed to culture before antibiotics 2, 1
• Negative leukocyte esterase + negative nitrite = effectively rules out UTI in most cases 1
• 10-50% of culture-proven UTIs have false-negative urinalysis in febrile infants <2 years, so culture is mandatory regardless of urinalysis results 1, 6

Microscopic Examination

Pyuria threshold: ≥10 WBCs/high-power field is considered positive 2, 1

Pyuria of 10-25 WBC/hpf has likelihood ratio of 18-19 for UTI when >20/hpf 5

Management Algorithm

If Symptomatic (fever, dysuria, urgency, frequency):

1. Obtain properly collected urine specimen immediately 1
2. Send for culture and antimicrobial susceptibility testing before starting antibiotics 1, 5
3. If child appears ill, toxic, or has high fever/systemic symptoms, start empiric antibiotics immediately after obtaining culture 5

First-line empiric options:

• Trimethoprim-sulfamethoxazole (higher cure rates than amoxicillin due to E. coli resistance) 3
• Nitrofurantoin 100mg twice daily for 5-7 days (if age-appropriate and CrCl ≥30 mL/min) 5
• Cephalosporins (cefazolin or cefuroxime for suspected E. coli, 94-98% sensitive) 5

If Asymptomatic:

Do not treat asymptomatic bacteriuria with pyuria—this provides no clinical benefit and promotes antibiotic resistance 1

Special Considerations for Children

Age-Specific Factors:

Infants 2-24 months with fever:

• All require urine evaluation (except circumcised boys >12 months) 3
• Uncircumcised male infants have substantially higher bacteriuria rate (36% vs 1.6% in circumcised) 2
• Culture is mandatory even with negative urinalysis 1, 6

Young infants:

• Have particularly poor nitrite sensitivity due to frequent voiding and short bladder dwell time 6
• Nitrite sensitivity only 19-48% despite 98-100% specificity 1

Imaging Recommendations:

Ultrasound of urinary tract is advised within 24 hours to exclude obstructive uropathy in children with febrile UTI 4

Further imaging (VCUG, renal cortical scan) should be considered:

• If symptoms recur or persist 5
• To evaluate for vesicoureteral reflux depending on sex, age, and clinical presentation 4
• In children with recurrent UTIs 3

Critical Pitfalls to Avoid

1. Do not rule out UTI based solely on negative nitrites—this would miss 47-61% of true infections 5
2. Do not treat based on urinalysis alone without culture—you need culture confirmation to distinguish true UTI from asymptomatic bacteriuria 5
3. Do not accept bag-collected specimens for definitive diagnosis—positive results require catheterized confirmation 1, 5
4. Do not ignore pyuria in febrile infants <2 years—obtain culture regardless of other urinalysis findings 1, 6
5. Do not delay culture collection—always obtain before starting antibiotics 1, 5

Follow-Up Considerations

Address constipation and bladder/bowel dysfunction in toilet-trained children to help prevent recurrent UTIs 3, 4

Prophylactic antibiotics do not reduce risk of subsequent UTIs, even in children with mild to moderate vesicoureteral reflux 3