Diagnosing and Treating Pediatric UTI
Diagnostic Approach
Diagnosis requires both pyuria AND ≥50,000 CFU/mL of a single uropathogen on properly collected urine culture. 1, 2
Urine Collection Method
- In non-toilet-trained children, obtain urine by urethral catheterization or suprapubic aspiration—never use bag specimens for culture due to unacceptably high false-positive rates (70% specificity, 85% false-positive rate). 1, 2, 3
- In toilet-trained children, collect midstream clean-catch urine after cleaning external genitalia. 2, 4
- Always obtain urine culture BEFORE starting antibiotics—this is your only opportunity for definitive diagnosis and antibiotic adjustment. 2, 3
Urinalysis Interpretation
- Positive urinalysis includes: dipstick positive for leukocyte esterase OR nitrites, OR microscopy showing ≥10 WBC/mm³ or bacteria. 2, 3
- Urinalysis alone does not provide definitive diagnosis—culture confirmation is mandatory. 3
Clinical Presentation by Age
- Infants <2 years: Fever is the most common symptom; expect nonspecific presentations including vomiting, diarrhea, irritability, poor feeding, or foul-smelling urine. 3
- Older children: May present with dysuria, frequency, urgency, or abdominal pain. 5
- Risk factors: Uncircumcised boys (especially <6 months), girls >1 year, fever without source in children <1 year. 3
Treatment Algorithm
Initial Antibiotic Selection
For febrile UTI/pyelonephritis, start oral antibiotics immediately if the child is well-appearing and can tolerate oral intake; reserve parenteral therapy for toxic-appearing children or those unable to retain oral medications. 1, 2, 3
First-Line Oral Options:
- Amoxicillin-clavulanate: 20-40 mg/kg/day divided into 3 doses 2, 3
- Cephalosporins: Cefixime 8 mg/kg/day in 1 dose OR cephalexin 50-100 mg/kg/day in 4 doses 2
- Trimethoprim-sulfamethoxazole: 40 mg/kg sulfamethoxazole + 8 mg/kg trimethoprim per 24 hours divided every 12 hours (only if local resistance <10% for pyelonephritis) 2, 6
Parenteral Option:
- Ceftriaxone: 50-75 mg/kg IV/IM every 24 hours for toxic-appearing children, inability to retain oral intake, or age <3 months 2, 3
Treatment Duration
For febrile UTI/pyelonephritis: 7-14 days total (10 days most commonly supported). 1, 2, 3
- Do not treat for less than 7 days—shorter courses are inferior for febrile UTI. 1, 2
- For uncomplicated cystitis in children >2 years: 3-5 days may be sufficient. 2
Critical Medication Considerations
- Never use nitrofurantoin for febrile UTI/pyelonephritis—it does not achieve adequate serum/parenchymal concentrations to treat pyelonephritis. 2
- Avoid fluoroquinolones in children due to musculoskeletal safety concerns; reserve only for severe infections where benefits outweigh risks. 2
- Neonates (<28 days) require hospitalization and parenteral therapy with ampicillin + aminoglycoside or third-generation cephalosporin for 14 days total. 2
Antibiotic Adjustment
- Adjust antibiotics based on culture and sensitivity results when available (typically 48-72 hours). 1, 2
- Consider local antibiotic resistance patterns when selecting empiric therapy. 1, 2
Imaging Recommendations
Renal and Bladder Ultrasound (RBUS)
Obtain RBUS for ALL children <2 years with first febrile UTI to detect anatomic abnormalities. 1, 2, 3
- Perform after initiating treatment; patient should be well-hydrated with bladder distended. 2
- For children >2 years with first uncomplicated UTI, RBUS is NOT routinely required. 2
- Consider RBUS if fever persists >48 hours on appropriate therapy, recurrent UTIs, or non-E. coli organisms. 2
Voiding Cystourethrography (VCUG)
VCUG is NOT recommended routinely after first UTI. 1, 2
Indications for VCUG:
- RBUS shows hydronephrosis, scarring, or findings suggesting high-grade vesicoureteral reflux (VUR) or obstructive uropathy 1, 2
- After second febrile UTI 1, 2
- Fever persists >48 hours on appropriate therapy 2
- Consider in boys <2 months due to higher VUR prevalence 2
Follow-Up Strategy
Short-Term Follow-Up (1-2 Days)
Clinical reassessment within 1-2 days is critical to confirm response to antibiotics and fever resolution. 2
- If fever persists beyond 48 hours of appropriate therapy, reevaluate diagnosis and consider antibiotic resistance or anatomic abnormalities. 1, 2
- This early follow-up allows detection of treatment failure before complications develop. 2
Long-Term Follow-Up
- No routine scheduled visits after successful treatment of first uncomplicated UTI. 1, 2
- Instruct parents to seek prompt medical evaluation (within 48 hours) for any future febrile illness to detect recurrent UTI early. 2, 3
- Obtain urine specimen at onset of subsequent febrile illnesses. 3
Antibiotic Prophylaxis
Routine antibiotic prophylaxis is NOT recommended after first UTI or for children with VUR grades I-IV. 1, 2
- Data from recent studies do not support prophylaxis to prevent febrile recurrent UTI in infants without VUR or with grade I-IV VUR. 1
- Consider prophylaxis selectively only in high-risk patients (recurrent febrile UTI, high-grade VUR), weighing benefits against microbial resistance risk. 2
- The RIVUR trial showed prophylaxis reduced recurrent UTI by ~50% but did not reduce renal scarring. 2
Special Considerations
Age-Specific Concerns
- Neonates (<28 days): Require hospitalization, parenteral therapy, and 14 days total treatment. 2
- Infants 29-60 days: Ceftriaxone IV/IM is standard; oral therapy acceptable if well-appearing, stable, and feeding well. 2
- Children >2 years: Can often be managed with shorter courses (3-5 days) for uncomplicated cystitis. 2
Distinguishing Cystitis from Pyelonephritis
- In young children unable to verbalize symptoms, assess for systemic signs: fever, poor feeding, irritability, vomiting. 1
- Clinical evaluation combined with urinalysis and imaging studies are essential for differentiation. 1
- Fever is the most reliable indicator of upper tract involvement in young children. 3
Critical Pitfalls to Avoid
- Do not delay treatment—early antimicrobial therapy (within 48 hours of fever onset) reduces renal scarring risk by >50%. 2, 3
- Do not use bag specimens for culture—they have unacceptably high false-positive rates. 2, 3
- Do not use nitrofurantoin for febrile UTI—inadequate tissue penetration for pyelonephritis. 2
- Do not treat for <7 days for febrile UTI—shorter courses are inferior. 1, 2
- Do not fail to obtain culture before antibiotics—this is your only opportunity for definitive diagnosis. 2
- Do not routinely perform VCUG after first UTI—reserve for specific indications. 1, 2
When to Refer
Refer to pediatric nephrology/urology for:
- Abnormal RBUS showing hydronephrosis, scarring, or structural abnormalities 2
- Recurrent febrile UTIs (≥2 episodes) 2
- Poor response to appropriate antibiotics within 48 hours 2
- Non-E. coli organisms or suspected complicated infection 2