What is the recommended evaluation and empiric treatment for a urinary tract infection in a female child?

Evaluation and Empiric Treatment of UTI in Female Children

For female children with suspected UTI, obtain a properly collected urine specimen (catheterized if <2 years or non-toilet-trained, clean-catch if older) for culture before starting antibiotics, then initiate oral therapy with amoxicillin-clavulanate, a cephalosporin, or trimethoprim-sulfamethoxazole (only if local E. coli resistance <10-20%) for 7-14 days for febrile UTI or 7-10 days for uncomplicated cystitis. 1, 2

Diagnostic Approach

Urine Collection Method

• Non-toilet-trained or <2 years: Obtain urine by catheterization or suprapubic aspiration—bag specimens should never be used for culture due to 85% false-positive rates 1, 2
• Toilet-trained children: Midstream clean-catch specimen is acceptable 1
• Critical: Collect specimen before starting antibiotics to ensure accurate culture results 1, 2

Diagnostic Criteria

• 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 2
• Combined negative dipstick for leukocyte esterase and nitrite with negative microscopy provides 95-98% negative predictive value 2
• Positive nitrite has 98-100% specificity for UTI 2

Empiric Antibiotic Selection

First-Line Oral Options (Age-Specific)

For febrile UTI/pyelonephritis:

• Amoxicillin-clavulanate 40-45 mg/kg/day divided every 12 hours 2
• Cephalosporins: Cefixime 8 mg/kg/day once daily, cephalexin 50-100 mg/kg/day divided into 4 doses, or cefpodoxime 1, 2
• Trimethoprim-sulfamethoxazole: Only if local E. coli resistance <10% 1, 2

For uncomplicated cystitis (non-febrile):

• Nitrofurantoin is preferred as it spares broader-spectrum agents 2
• Never use nitrofurantoin for febrile UTI as it doesn't achieve adequate serum/parenchymal concentrations to treat pyelonephritis 1, 2

Parenteral Therapy Indications

Reserve IV antibiotics for children who:

• Appear toxic or septic 1
• Cannot retain oral intake 1
• Are <3 months old 2
• Have uncertain compliance 2

Parenteral option: Ceftriaxone 50 mg/kg IV/IM every 24 hours 1, 2

Critical Resistance Considerations

• Amoxicillin monotherapy is contraindicated: WHO removed it from empiric recommendations due to 75% (range 45-100%) global E. coli resistance 2
• Trimethoprim-sulfamethoxazole resistance: E. coli resistance reaches 19-63% in some studies; use only when local resistance <10% for pyelonephritis or <20% for cystitis 1, 2
• Always adjust therapy based on culture and sensitivity results when available 1, 2

Treatment Duration

By Clinical Presentation

• Febrile UTI/pyelonephritis: 7-14 days total (10 days most common) 1, 2
• Uncomplicated cystitis (non-febrile): 7-10 days 2
• Courses <7 days are inferior for febrile UTIs and should be avoided 1, 2

Age-Specific Considerations

• Neonates (<28 days): Require hospitalization and 14 days of parenteral therapy (ampicillin + aminoglycoside or third-generation cephalosporin) 2
• Infants 29 days-3 months: May use oral therapy if well-appearing and stable, but consider parenteral option 2

Imaging Recommendations

First Febrile UTI

Age <2 months:

• Renal/bladder ultrasound: 9/9 rating (usually appropriate) 3
• VCUG: 6/9 rating (may be appropriate), especially in boys 3

Age 2 months-6 years:

• Renal/bladder ultrasound: 7/9 rating (usually appropriate) 3
• VCUG: 4/9 rating (may be appropriate)—not routine after first UTI 3
• VCUG indicated if ultrasound shows hydronephrosis, scarring, or findings suggesting high-grade VUR/obstruction 3

Age >6 years:

• Renal/bladder ultrasound: 5/9 rating (disagreement among experts)—generally not required for uncomplicated first UTI 3, 1
• VCUG: 3/9 rating (usually not appropriate) 3

First Non-Febrile UTI (Cystitis)

• No routine imaging required for uncomplicated cystitis at any age 2
• Imaging only indicated for recurrent UTI, atypical presentation, or poor response to therapy 3, 1

Indications for Imaging Regardless of Age

Obtain renal/bladder ultrasound if:

• Poor response to antibiotics within 48 hours 3, 1
• Septic or seriously ill appearance 3, 1
• Poor urine stream 3
• Elevated creatinine 3, 1
• Non-E. coli organism 3, 1
• Recurrent UTI 3, 1

VCUG Timing

• Not routinely after first UTI 3, 1
• Perform after second febrile UTI 3, 1
• Consider if ultrasound abnormal or fever persists >48 hours on appropriate therapy 3, 1

DMSA Scan

• Not appropriate for immediate post-treatment evaluation (3/9 rating) 3
• Reserve for 4-6 months after infection to assess for renal scarring 3
• May be appropriate for follow-up of children with VUR to detect new scarring, especially after febrile UTI 3

Follow-Up Strategy

Short-Term (1-2 Days)

• Clinical reassessment within 24-48 hours is critical to confirm fever resolution and clinical improvement 1, 2
• If fever persists >48 hours despite appropriate therapy, reevaluate for antibiotic resistance, anatomic abnormality, or abscess 1, 2

Long-Term

• No routine scheduled visits after successful treatment of uncomplicated first UTI 1, 2
• Instruct parents to seek prompt evaluation (within 48 hours) for any future febrile illness to detect recurrent UTI early 1, 2

After Second UTI

• Obtain VCUG to evaluate for vesicoureteral reflux 1

Antibiotic Prophylaxis

Not routinely recommended after first UTI 2

Consider selectively for:

• Recurrent febrile UTIs (≥2 episodes) 1, 2
• High-grade VUR (grades III-V) with recurrent infections 1
• Bowel/bladder dysfunction with VUR 2

Evidence: RIVUR trial showed prophylaxis reduced recurrent UTI by ~50% in children with VUR but did not reduce renal scarring 1, 2

Critical Pitfalls to Avoid

• Do not delay antibiotic treatment if febrile UTI is suspected—early treatment (within 48 hours) reduces renal scarring risk by >50% 1, 2
• Do not use nitrofurantoin for febrile UTI as it lacks adequate tissue penetration for pyelonephritis 1, 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 the only opportunity for definitive diagnosis 1, 2
• Do not treat asymptomatic bacteriuria—may be harmful and lead to resistant organisms 1
• Do not order routine imaging for first uncomplicated cystitis or for children >6 years with first uncomplicated febrile UTI 3, 1, 2
• Do not use amoxicillin monotherapy empirically due to 75% global E. coli resistance 2

When to Refer

Refer to pediatric nephrology/urology for:

• Recurrent febrile UTIs (≥2 episodes) 1
• Abnormal renal ultrasound showing hydronephrosis, scarring, or structural abnormalities 1
• Poor response to appropriate antibiotics within 48 hours 1
• Non-E. coli organisms or suspected complicated infection 1

Long-Term Complications

• Approximately 15% of children develop renal scarring after first UTI 1, 4
• Renal scarring can lead to hypertension (5% of cases) and chronic kidney disease (3.5% of ESRD cases) 1, 4
• Early treatment and prevention of recurrent UTI lower the risk of scarring 1, 5