Pediatric Urinary Tract Infection: Evaluation, Treatment, and Imaging
Diagnostic Approach
Obtain urine by catheterization or suprapubic aspiration in non-toilet-trained children before starting antibiotics; bag specimens should never be used for culture. 1, 2 In toilet-trained children, collect a midstream clean-catch specimen for both urinalysis and culture. 2
When to Suspect UTI
- Febrile infants 2-24 months with no obvious source of fever should be evaluated for UTI, particularly if they have risk factors: non-black race, temperature ≥39°C (102.2°F), fever >24 hours, or absence of another infection source. 1
- Older children presenting with dysuria, urinary frequency, hematuria, abdominal pain, back pain, or new daytime incontinence warrant evaluation. 3
Diagnostic Criteria
UTI diagnosis requires BOTH pyuria (≥5 WBC/HPF on centrifuged specimen or positive leukocyte esterase) AND ≥50,000 CFU/mL of a single uropathogen on culture. 1, 2, 4 The threshold was reduced from 100,000 CFU/mL based on reexamination of evidence showing that 50,000 CFU/mL from a properly collected specimen is diagnostic. 1
Critical Diagnostic Pitfall
A negative urinalysis does not rule out UTI in young infants. Leukocyte esterase sensitivity drops to only 46-69% in infants ≤90 days old. 5 If clinical suspicion is high in a febrile infant, obtain culture regardless of urinalysis results. 6
Antimicrobial Therapy
Start oral antibiotics immediately after obtaining urine culture for children who are not toxic-appearing and can tolerate oral intake; oral and parenteral routes are equally effective. 1, 2
First-Line Oral Antibiotics
- Amoxicillin-clavulanate 40-45 mg/kg/day divided every 12 hours 2
- Cephalosporins: cefixime 8 mg/kg once daily, cephalexin 50-100 mg/kg/day divided into 4 doses, or cefpodoxime 2, 4
- Trimethoprim-sulfamethoxazole ONLY if local E. coli resistance is <10% for febrile UTI or <20% for cystitis 2, 4
Do NOT use amoxicillin monotherapy empirically—global surveillance shows 75% (range 45-100%) of E. coli urinary isolates are resistant, making it unreliable. 2 The WHO removed amoxicillin from first-line recommendations in 2021 based on this data. 2
Parenteral Therapy Indications
Reserve IV/IM therapy for: 1, 2
- Toxic appearance
- Unable to retain oral intake
- Age <3 months (requires hospitalization)
- Uncertain compliance
Ceftriaxone 50 mg/kg IV/IM every 24 hours is the standard parenteral choice. 2 Neonates ≤28 days require ampicillin + gentamicin or third-generation cephalosporin for 14 days total. 2
Treatment Duration
- Febrile UTI/pyelonephritis: 7-14 days (10 days most common) 1, 2, 4
- Non-febrile UTI/cystitis: 7-10 days 2, 4
Courses shorter than 7 days are inferior for febrile UTIs and should never be used. 1, 2 The committee identified optimal duration as an area needing further research but found clear evidence against short courses. 1
Critical Antibiotic Pitfalls
- Never use nitrofurantoin for febrile UTI—it does not achieve adequate serum/parenchymal concentrations to treat pyelonephritis. 2, 4
- Adjust antibiotics based on culture results when available, considering local resistance patterns. 2, 4
- Early treatment within 48 hours reduces renal scarring risk by >50%. 2
Imaging Recommendations
Renal and Bladder Ultrasound (RBUS)
All febrile infants <2 years with first UTI should undergo RBUS to detect anatomic abnormalities. 1, 2, 4 The American College of Radiology rates this 7-9/9 ("usually appropriate"). 2 RBUS involves no radiation and is the safest initial imaging. 2
For children >2 years with first uncomplicated UTI, routine imaging is NOT indicated. 2, 4 Order RBUS only if: 2, 4
- Poor response to antibiotics within 48 hours
- Septic or seriously ill appearance
- Non-E. coli organism cultured
- Elevated creatinine
- Obstructive urine stream
Voiding Cystourethrography (VCUG)
VCUG is NOT recommended routinely after first UTI. 1, 2, 4 This represents the biggest change from previous guidelines. 1 The RIVUR trial showed prophylaxis reduces recurrent UTI by 50% in children with VUR but does not reduce renal scarring, indicating early VUR detection after first UTI does not improve long-term outcomes. 2
- RBUS reveals hydronephrosis, scarring, or findings suggesting high-grade VUR or obstructive uropathy
- Second febrile UTI occurs
- Fever persists >48 hours on appropriate therapy
- Age <2 months (especially boys)—higher VUR prevalence
DMSA Scan
Do NOT order DMSA scan acutely or immediately post-treatment. 2 Reserve DMSA renal cortical scintigraphy for 4-6 months after infection to assess for renal scarring in selected cases (known VUR, recurrent UTI). 2 The American College of Radiology rates acute DMSA 3/9 ("usually not appropriate"). 2
Follow-Up Strategy
Clinical reassessment within 1-2 days is critical to confirm fever resolution and clinical improvement. 2 This early follow-up detects treatment failure before complications develop. 2
No routine scheduled visits are necessary after successful treatment of first uncomplicated UTI. 2, 4 Instead, instruct parents to seek prompt evaluation (ideally within 48 hours) for any future febrile illness to detect recurrent UTI early. 1, 2, 4
When Fever Persists
If fever continues beyond 48 hours on appropriate antibiotics: 2
- Reevaluate diagnosis
- Consider antibiotic resistance
- Evaluate for anatomic abnormalities or abscess
- Consider RBUS if not yet obtained
After Second Febrile UTI
Obtain VCUG after a second febrile UTI—risk of grade IV-V VUR increases to approximately 18%. 2, 4
Common Pitfalls to Avoid
- Using bag specimens for culture (70% specificity = 85% false-positive rate) 2
- Failing to obtain culture before antibiotics—this is the only opportunity for definitive diagnosis 2, 4
- Using nitrofurantoin for febrile UTI/pyelonephritis 2, 4
- Treating for <7 days for febrile UTI 1, 2
- Ordering routine VCUG after first UTI 1, 2, 4
- Ordering routine imaging for non-febrile first UTI in children >2 years 2, 4
- Treating asymptomatic bacteriuria—it is the host inflammatory response (fever + pyuria) that causes scarring, not bacteriuria alone 1
- Delaying treatment—early therapy reduces scarring risk 2
Age-Specific Considerations
Neonates ≤28 Days
- Require hospitalization and parenteral therapy (ampicillin + gentamicin or third-generation cephalosporin) 2
- Complete 14 days total therapy 2
- Higher risk of bacteremia and complications 2
Infants 29 Days to 3 Months
- Consider hospitalization if toxic-appearing 2
- Ceftriaxone 50 mg/kg IV/IM every 24 hours for parenteral therapy 2
- Well-appearing infants may receive oral therapy (cefixime or cephalexin) 2