What is the first-line treatment for a child with a urinary tract infection (UTI)?

First-Line Treatment for Pediatric UTI

For most children with urinary tract infections, oral antibiotics for 7-14 days are the first-line treatment, with cephalosporins, amoxicillin-clavulanate, or trimethoprim-sulfamethoxazole as the preferred agents, chosen based on local resistance patterns. 1, 2, 3

Initial Antibiotic Selection

Oral therapy is appropriate for the majority of children unless they meet specific criteria for parenteral treatment 1, 2:

• First-line oral options include:
  • Cephalosporins (cefixime, cefpodoxime, cefprozil, cefuroxime axetil, cephalexin) 1, 2, 3
  • Amoxicillin-clavulanate at 40-45 mg/kg/day divided every 12 hours 1, 3
  • Trimethoprim-sulfamethoxazole at 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours in two divided doses 1, 4

Reserve parenteral therapy for 1, 2:

• Children appearing "toxic" or seriously ill
• Inability to retain oral medications
• Uncertain compliance with oral therapy
• Age <3 months (especially neonates <28 days who require hospitalization) 1

For parenteral treatment, use ceftriaxone 50 mg/kg IV/IM every 24 hours 1

Treatment Duration

The total course should be 7-14 days for febrile UTI/pyelonephritis, with 10 days being the most commonly recommended duration 1, 2, 3. Shorter courses of 1-3 days are inferior and should be avoided for febrile UTIs 1, 2, 3.

For uncomplicated cystitis (non-febrile UTI), 7-10 days is appropriate, though shorter courses of 3-5 days may be comparable in children >2 years 1.

Critical Selection Considerations

Always consider local antibiotic resistance patterns when selecting empiric therapy 1, 2, 3:

• Use trimethoprim-sulfamethoxazole only if local E. coli resistance is <10% for pyelonephritis 1
• Adjust antibiotics based on culture and sensitivity results when available 1, 3

Avoid nitrofurantoin for febrile UTIs as it does not achieve adequate serum/parenchymal concentrations to treat pyelonephritis 1, 2, 3. Nitrofurantoin should only be used for uncomplicated cystitis 1.

Age-Specific Algorithms

Neonates (<28 days) 1, 5:

• Require hospitalization and parenteral therapy
• Use ampicillin + aminoglycoside or third-generation cephalosporin
• Complete 14 days total therapy

Infants 28 days to 3 months 1, 5:

• If clinically ill: hospitalize with parenteral third-generation cephalosporin or gentamicin
• If well-appearing: may use outpatient parenteral ceftriaxone until afebrile for 24 hours, then complete 14 days with oral antibiotics

Children >3 months 1, 2, 3:

• Most can be treated with oral antibiotics from the start
• Use parenteral therapy only if meeting criteria above

Monitoring and Follow-Up

Expect clinical improvement within 24-48 hours of starting appropriate antibiotics 1, 2. If fever persists beyond 48 hours, reevaluate for treatment failure, antibiotic resistance, or anatomic abnormalities 1.

Obtain urine culture before starting antibiotics to guide therapy adjustments and confirm diagnosis 1.

Imaging Recommendations

For children <2 years with first febrile UTI, obtain renal and bladder ultrasound (RBUS) to detect anatomic abnormalities 1, 6.

Voiding cystourethrography (VCUG) is NOT routinely recommended after first UTI but should be performed after a second febrile UTI or if RBUS shows hydronephrosis, scarring, or findings suggesting high-grade vesicoureteral reflux 1, 6.

Common Pitfalls to Avoid

• Never use nitrofurantoin for febrile UTIs/pyelonephritis 1, 2, 3
• Never treat for less than 7 days for febrile UTI 1, 2
• Never fail to obtain urine culture before starting antibiotics 1
• Never treat asymptomatic bacteriuria, as this may lead to resistant organisms 1, 3
• Never ignore local resistance patterns when selecting empiric therapy 1, 2
• Never delay treatment as early antimicrobial therapy (within 48 hours) reduces risk of renal scarring by >50% 1