In a 35-year-old man with sudden severe left ear pain, mild hearing loss, recent resolved upper respiratory symptoms, and an otoscopic image showing a markedly erythematous, edematous external auditory canal, what is the most likely diagnosis?

Acute Otitis Externa

Based on the clinical presentation of severe left ear pain, recent upper respiratory infection, mild hearing loss, and an otoscopic image showing a markedly erythematous and edematous external auditory canal, the most likely diagnosis is acute otitis externa (option 4). 1, 2

Diagnostic Reasoning

The clinical picture is classic for acute otitis externa:

• Rapid onset of severe ear pain following an upper respiratory infection with congestion and rhinorrhea 1, 3
• Hearing loss in the affected ear, which occurs due to canal edema and debris 1, 3
• Erythematous, edematous external auditory canal on otoscopy 1, 2, 3
• Hallmark finding: Intense tenderness with tragus or pinna manipulation (though not explicitly stated, this should be assessed) 1, 2, 3

The recent URI likely introduced moisture and inflammation to the ear canal, creating an environment conducive to bacterial overgrowth—primarily Pseudomonas aeruginosa (20-60%) and Staphylococcus aureus (10-70%). 3, 4

Why Other Diagnoses Are Less Likely

• Bullous myringitis (option 1): Would show hemorrhagic bullae on the tympanic membrane, not diffuse canal inflammation 1
• Cholesteatoma (option 2): A chronic condition presenting with painless otorrhea and white debris behind an intact or perforated tympanic membrane, not acute severe pain 1
• Granulomatosis with polyangiitis (option 3): A systemic vasculitis that would present with constitutional symptoms, chronic ear disease, and other organ involvement—not isolated acute ear pain 1
• Ramsay Hunt syndrome (option 5): Would present with vesicular eruptions on the pinna/canal, facial paralysis, and severe pain—vesicles are the key distinguishing feature 1

Immediate Management Algorithm

Step 1: Perform Aural Toilet

Before any medication, the ear canal must be cleared of debris, cerumen, and inflammatory material to ensure drops reach infected tissue. 1, 2, 5

• Use gentle suction, dry mopping, or irrigation with body-temperature water/saline 1, 2
• Critical caveat: If the patient were diabetic or immunocompromised, use only atraumatic suction under microscopy—never irrigate, as this can trigger necrotizing otitis externa 2, 5, 3

Step 2: Select Topical Antimicrobial Therapy

Topical antibiotic drops are the definitive first-line treatment—oral antibiotics should NOT be prescribed initially. 1, 2, 3

If tympanic membrane integrity is uncertain (which it is in this case with severe canal edema):

• Use only non-ototoxic fluoroquinolones: ofloxacin 0.3% or ciprofloxacin 0.2% 1, 2, 3
• Avoid aminoglycoside-containing drops (neomycin/polymyxin B) due to ototoxicity risk 1, 2

If tympanic membrane is confirmed intact:

• Any FDA-approved preparation is acceptable (fluoroquinolones, neomycin/polymyxin B/hydrocortisone, or acetic acid 2%) 1, 2, 3
• Clinical cure rates are 65-90% within 7-10 days regardless of agent 1, 2, 5

Step 3: Ensure Proper Drop Administration

Only 40% of patients self-administer drops correctly—provide explicit instructions: 2

• Warm bottle in hands for 1-2 minutes to prevent dizziness 2
• Lie with affected ear upward 2
• Fill canal completely with drops 2
• Remain in position for 3-5 minutes (use a timer) 2
• Apply gentle tragal pumping or pinna movement to eliminate trapped air 2
• Have someone else administer drops if possible—this significantly improves adherence 2

Step 4: Prescribe Adequate Analgesia

Pain assessment and appropriate analgesics are essential—otitis externa pain is often severe and disproportionate to visual findings. 1, 2, 3

• Mild-to-moderate pain: Acetaminophen 650-1000 mg every 6 hours or ibuprofen 400-600 mg every 6 hours 2
• Severe pain (as in this case): Short-term opioid-containing analgesics for the initial 48-72 hours 2, 3
• Reassure the patient: Pain typically improves within 48-72 hours of starting topical therapy 1, 2, 5, 3

Step 5: Treatment Duration and Follow-Up

• Prescribe drops for a minimum of 7 days, even if symptoms resolve earlier, to prevent relapse 1, 2, 5
• Reassess within 48-72 hours if no improvement occurs 1, 2, 5

When to Escalate to Systemic Antibiotics

Oral antibiotics are NOT indicated for this uncomplicated case. 1, 2, 3 They achieve only 30-67% cure rates versus 77-96% with topical therapy. 2

Reserve systemic antibiotics for:

• Extension of infection beyond the ear canal (periauricular cellulitis/swelling) 1, 2, 3
• Diabetes mellitus or immunocompromised state 1, 2, 3
• Severe canal edema preventing adequate topical delivery despite wick placement 1, 2
• Failure to improve after 48-72 hours of appropriate topical therapy 1, 2, 3

When systemic therapy is indicated: Use fluoroquinolones (ciprofloxacin 500 mg twice daily) to cover P. aeruginosa and S. aureus. 2, 3

Common Pitfalls to Avoid

• Prescribing oral antibiotics for uncomplicated cases—occurs inappropriately in 20-40% of patients 2
• Skipping aural toilet before drop administration—medication cannot penetrate debris 1, 2
• Using ototoxic preparations when tympanic membrane integrity is uncertain 1, 2
• Inadequate pain management—this is a severely painful condition requiring aggressive analgesia 1, 2, 3
• Failing to provide proper drop administration instructions—most patients do this incorrectly 2

Patient Education

• Keep the ear dry during treatment—cover with petroleum jelly-coated cotton or earplug before showering 2
• Avoid swimming and water exposure until infection resolves 2
• Do not insert cotton swabs or any objects into the ear canal 2
• Complete the full 7-day course even if symptoms resolve early 2, 5
• Return for reassessment if symptoms don't improve within 48-72 hours or persist beyond 2 weeks 2