What is the treatment for urinary tract infections (UTIs) in infants?

Treatment of Urinary Tract Infections in Infants

For infants 2-24 months with confirmed UTI, initiate antimicrobial therapy for 7-14 days using either oral or parenteral antibiotics based on clinical appearance, with oral therapy being equally effective as parenteral in non-toxic-appearing infants. 1, 2

Immediate Treatment Decision

Start antibiotics promptly (ideally within 48 hours of fever onset) to limit renal damage and prevent scarring. 1, 3

Route of Administration Algorithm

• Oral therapy is appropriate for infants who:

  • Do not appear toxic 1, 2
  • Can retain oral fluids 4
  • Have reliable follow-up 4

• Parenteral therapy is required for infants who:

  • Appear toxic or ill 1, 2
  • Cannot retain oral intake 4
  • Are younger than 2-3 months of age 2
  • Fail to respond within 48 hours of oral therapy 2

Antibiotic Selection

Base initial choice on local antimicrobial sensitivity patterns and adjust according to culture results. 1, 3

Oral Options (First-Line)

• Amoxicillin-clavulanate: 20-40 mg/kg per day divided in 3 doses 1
• Cephalosporins: Cefixime, cefpodoxime, or cephalexin 1
• Trimethoprim-sulfamethoxazole (if local resistance patterns permit) 5

Parenteral Options

• Ceftriaxone: 75 mg/kg every 24 hours 1
• Cefotaxime: 150 mg/kg per day, divided every 6-8 hours 1
• Ampicillin plus gentamicin for infants ≤2 months 6

Critical Medication Pitfall

Never use nitrofurantoin for febrile UTI/pyelonephritis in infants, as it does not achieve adequate serum/parenchymal concentrations to treat kidney infection. 3

Treatment Duration

7-14 days total for febrile UTI/pyelonephritis. 1, 3 Shorter courses (1-3 days) are inferior and should not be used for febrile infections. 3

Diagnostic Requirements Before Treatment

Obtain urine by catheterization or suprapubic aspiration (never bag collection for culture) before starting antibiotics. 4, 2, 3 Diagnosis requires:

• Urinalysis showing pyuria and/or bacteriuria 4
• Culture with ≥50,000 CFUs/mL of a single uropathogen 4, 1

Both abnormal urinalysis AND positive culture are necessary to confirm true UTI rather than asymptomatic bacteriuria. 4

Follow-Up Protocol

Immediate (1-2 Days)

Clinical reassessment within 1-2 days is mandatory to confirm fever resolution and treatment response. 4, 3 If fever persists beyond 48 hours despite appropriate antibiotics, reevaluate for antibiotic resistance or anatomic abnormalities. 2, 3

Imaging After First Febrile UTI

Obtain renal and bladder ultrasonography after the first febrile UTI to detect anatomic abnormalities. 1, 2, 3 This should be performed even if the infant responds well to treatment. 7

Voiding cystourethrography (VCUG) is NOT routinely recommended after the first UTI. 4, 3 Perform VCUG only if:

• Ultrasound reveals hydronephrosis, scarring, or findings suggesting high-grade vesicoureteral reflux 3
• A second febrile UTI occurs 4, 3

Long-Term Monitoring

Instruct parents to seek prompt medical evaluation for any future febrile illness to ensure timely urine testing and treatment. 1, 2 No routine scheduled visits are needed after successful treatment of a first uncomplicated UTI. 3

Common Pitfalls to Avoid

• Delaying treatment beyond 48 hours increases renal scarring risk 1, 3
• Using bag specimens for culture leads to false positives (contamination rates 12-83%) and overtreatment 2, 3
• Treating for <7 days for febrile UTI results in treatment failure 3
• Failing to obtain culture before antibiotics prevents accurate diagnosis and sensitivity-guided therapy 3
• Routine VCUG after first UTI exposes infants to unnecessary radiation without proven benefit 4, 3

Antibiotic Resistance Considerations

Amoxicillin alone is no longer acceptable due to high E. coli resistance rates. 5 Always consider local resistance patterns when selecting empiric therapy, and adjust based on culture sensitivities when available. 1, 3