What imaging studies are recommended for a 15-year-old male with a Urinary Tract Infection (UTI)?

Imaging Recommendations for UTI in a 15-Year-Old Male

For a 15-year-old male with a urinary tract infection (UTI), ultrasound of the kidneys and bladder is the only imaging study typically recommended, as routine imaging beyond this is not indicated for a first UTI in this age group.

Initial Imaging Approach

• Ultrasound of the kidneys and bladder is the primary imaging modality for adolescents with UTI, though even this may not be necessary for a first uncomplicated UTI in a patient over 6 years of age 1
• The incidence of new-onset UTI in children >6 years is low and often associated with behavioral abnormalities, dysfunctional elimination syndrome, or initiation of sexual intercourse in adolescents 1
• Males are less commonly affected by UTI in this age group compared to females 1
• The likelihood of detecting previously unknown underlying renal anomalies is low in adolescents with first-time UTI 1

Evidence-Based Recommendations by Age Group

• The ACR Appropriateness Criteria specifically addresses different age groups:
  • For children <2 months: More conservative imaging approach is needed due to higher risk of sepsis and renal anomalies 1
  • For children 2 months to 6 years: Ultrasound is usually appropriate for first febrile UTI 1
  • For children >6 years (including 15-year-olds): There is usually no need for imaging to guide treatment for a first febrile UTI with good response to treatment 1

When Additional Imaging May Be Warranted

Additional imaging should be considered in the following circumstances:

• Atypical or complicated UTI presentation, including:

  • Poor response to antibiotics within 48 hours 1
  • Sepsis 1
  • Poor urine stream 1
  • Elevated creatinine 1
  • Non-E. coli UTI 1
  • Recurrent UTI 1

• If any of these conditions are present, consider:

  • Voiding cystourethrography (VCUG) or nuclear medicine cystography to evaluate for vesicoureteral reflux (VUR) 1
  • DMSA renal scan to evaluate for pyelonephritis or renal scarring in recurrent cases 1

Limitations of Ultrasound

• Ultrasound alone has limited sensitivity for detecting:
  • Vesicoureteral reflux (VUR) 1, 2
  • Renal parenchymal abnormalities 1, 2
  • Pyelonephritis (detects only about 25% of acute cases) 1
  • Renal scarring (detects only about 40% of cases) 1
• One study showed ultrasound sensitivity of 66.7%, specificity of 37.5%, with a negative predictive value of 81.8% 2

Advanced Imaging Considerations

• CT is generally not indicated for uncomplicated UTI in adolescents 1
• CT may be appropriate for evaluating complications such as renal abscess or xanthogranulomatous pyelonephritis 1
• MRI is not routinely used in UTI evaluation due to high cost, limited availability, and lack of evidence supporting its use in this context 1

Clinical Pitfalls to Avoid

• Avoid unnecessary radiation exposure from VCUG or CT in adolescents with first uncomplicated UTI 1
• Don't assume all UTIs in adolescent males require extensive imaging workup - this age group has lower prevalence of anatomic abnormalities compared to infants 1
• Remember that normal ultrasound findings don't completely exclude the possibility of VUR or renal scarring due to the limited sensitivity of ultrasound 1, 2
• Consider that UTI in adolescent males is less common than in females and may warrant investigation for underlying causes if recurrent 1