What investigations should be ordered for an 11-year-old with preauricular swelling and ear pain that started after swimming, with no discharge, and has not responded to two different antibiotics?

Investigations for Preauricular Swelling and Ear Pain in an 11-Year-Old After Swimming

For an 11-year-old with persistent preauricular swelling and ear pain that started after swimming and has not responded to two courses of antibiotics, a CT scan of the temporal bone is the most appropriate initial imaging investigation to rule out complications and identify the underlying cause. 1

Initial Assessment and Investigations

1. Otoscopic examination:

   • Assess for external auditory canal (EAC) obstruction or debris
   • Evaluate tympanic membrane integrity
   • Look for granulation tissue or signs of infection

2. Imaging studies:

   • CT scan of the temporal bone: First-line imaging to evaluate for:
     • Preauricular sinus infection/abscess 2
     • Extension of infection beyond the ear canal 1
     • Possible cholesteatoma 3
     • Soft tissue involvement

3. Laboratory tests:

   • Culture of any drainage: To identify causative organisms (commonly Pseudomonas aeruginosa or Staphylococcus aureus) 1, 4
   • Complete blood count: To assess for systemic infection

Differential Diagnosis to Consider

The preauricular swelling with ear pain that started after swimming and has not responded to antibiotics suggests several possibilities:

1. Preauricular sinus with infection/abscess: Common congenital abnormality that can become infected, especially after water exposure 2, 5

2. Necrotizing otitis externa: Given the prolonged course and failure of antibiotics 1, 4

3. Cholesteatoma with facial extension: Can cause preauricular swelling and may not respond to standard antibiotics 3

4. Parotid gland infection: Can present with preauricular swelling 6

Management Plan

Based on the findings from investigations:

1. If preauricular sinus abscess is confirmed:

   • Surgical excision is the definitive treatment (81% of cases require this) 5
   • Complete excision of the pit and sinus tract provides the only definitive cure 7, 2

2. If otitis externa is confirmed:

   • Topical therapy: Fluoroquinolone ear drops (ciprofloxacin 0.2% or ofloxacin 0.3%) 4
   • Aural toilet: To remove debris that may be blocking medication delivery 4
   • Pain management: Acetaminophen or NSAIDs 4

3. If extension beyond the ear canal is identified:

   • Systemic antibiotics targeting Pseudomonas and Staphylococcus 1, 4
   • Possible surgical intervention if abscess formation is present 3

Important Considerations

• The history of swimming suggests water exposure as a trigger, which commonly converts the normal acidic environment of the EAC to an alkaline one, predisposing to infection 1

• Failure of two courses of antibiotics indicates either:

  • Inappropriate antibiotic selection
  • Inadequate drug delivery due to canal obstruction
  • Presence of resistant organisms
  • Underlying anatomical abnormality (like preauricular sinus)

• Recurrent or persistent infections in the preauricular area after swimming strongly suggest a preauricular sinus, which has a prevalence of 4.4-9.3% in some populations 5

Follow-up Plan

• Reassessment within 48-72 hours if no improvement with new treatment 4
• If surgical excision is performed for a preauricular sinus, follow-up to monitor for recurrence (recurrence rates range from 9-42%) 2
• Consider auditory testing if preauricular sinus is confirmed, as 3-10% of cases may be associated with hearing abnormalities 2

This approach prioritizes identifying the underlying cause of the persistent preauricular swelling and ear pain to guide appropriate treatment and prevent complications.