What is the likely diagnosis for thick yellow‑green otorrhea from the left ear that dries to a brown crust?

Diagnosis: Acute Otitis Externa (Swimmer's Ear)

The thick yellow-green drainage from the left inner ear that dries to a brown crust is most consistent with acute otitis externa (AOE), a bacterial infection of the external auditory canal typically caused by Pseudomonas aeruginosa or Staphylococcus aureus. 1

Clinical Presentation

• Purulent otorrhea (thick yellow-green discharge) is a hallmark sign of acute otitis externa, representing inflammatory exudate containing bacteria, white blood cells, and cellular debris 1
• The brown dried crust forms when the purulent discharge dries on the external ear, a common finding in AOE 1
• Intense tragal or pinna tenderness should be present if this is AOE—this is the key distinguishing feature from middle ear disease 1

Critical Differential Diagnoses to Exclude

Chronic Suppurative Otitis Media (CSOM)

• CSOM presents with painless otorrhea through a tympanic membrane perforation, without the intense tragal tenderness seen in AOE 2, 1
• Pseudomonas aeruginosa is also the most common pathogen in CSOM, causing persistent purulent discharge 3
• Otoscopy will reveal a visible perforation in the tympanic membrane if CSOM is present 2, 4

Acute Otitis Media with Tympanostomy Tubes

• This causes painless otorrhea initially, without tragal tenderness 2
• The presence of visible tubes on otoscopy confirms this diagnosis 2

Fungal Otitis Externa (Otomycosis)

• White fuzzy exudate with pruritus suggests Aspergillus infection 1, 5
• A creamy discharge suggests Candida 5
• Yellow-green purulent discharge is more consistent with bacterial infection 1

Essential Physical Examination Findings

• Assess for tragal and pinna tenderness—intense tenderness disproportionate to visual findings confirms AOE 1
• Otoscopy must evaluate:
  • Canal edema, erythema, and purulent debris 1
  • Tympanic membrane integrity and mobility (pneumatic otoscopy when possible) 2, 1
  • Presence of perforation or tympanostomy tubes 2, 1
• Look for extension beyond the canal—periauricular cellulitis or swelling indicates complicated infection requiring systemic antibiotics 1
• Assess for modifying factors: diabetes, immunocompromised state, prior ear surgery, or radiation 2, 1

Treatment Algorithm

Step 1: Aural Toilet (Essential Pre-Treatment)

• Remove all debris, cerumen, and inflammatory material before any medication—drops cannot penetrate debris to reach infected tissue 1
• Use gentle suction, dry mopping, or irrigation with body-temperature water, saline, or hydrogen peroxide 1
• If the patient is diabetic or immunocompromised, use only atraumatic suction under microscopic guidance—avoid irrigation, which can precipitate necrotizing otitis externa 1, 6

Step 2: Topical Antimicrobial Therapy (First-Line)

• When tympanic membrane integrity is uncertain or compromised, use only non-ototoxic fluoroquinolone drops (ofloxacin 0.3% or ciprofloxacin 0.2%) 1
• When the tympanic membrane is intact, any FDA-approved topical preparation is acceptable—all achieve 65-90% clinical cure rates within 7-10 days 1
• Avoid aminoglycoside-containing drops (e.g., neomycin/polymyxin B) when tympanic membrane integrity is uncertain due to ototoxicity risk 1
• Prescribe for a minimum of 7 days even if symptoms resolve earlier, to prevent relapse 1

Step 3: Pain Management

• Assess pain severity and prescribe appropriate analgesics 1
• Mild-to-moderate pain: acetaminophen 650-1000 mg every 6 hours or ibuprofen 400-600 mg every 6 hours 1
• Severe pain: short-term opioid-containing analgesics for the initial 48-72 hours 1
• Pain typically improves within 48-72 hours of starting topical therapy 1

Step 4: When to Add Systemic Antibiotics

Oral antibiotics should NOT be used for uncomplicated AOE 1

Reserve systemic antibiotics for:

• Extension of infection beyond the ear canal (periauricular cellulitis or swelling) 1
• Diabetes mellitus or immunocompromised state 1, 6
• Severe canal edema preventing adequate topical drug delivery despite wick placement 1
• Failure to improve after 48-72 hours of appropriate topical therapy 1

When indicated, use fluoroquinolones (e.g., ciprofloxacin 500 mg twice daily) to cover Pseudomonas aeruginosa and Staphylococcus aureus, which cause approximately 98% of cases 1

Step 5: Reassessment

• Reassess within 48-72 hours if no improvement occurs 1
• Common causes of treatment failure include:
  • Inadequate drug delivery due to canal obstruction or poor adherence 1
  • Allergic contact dermatitis from topical agents (especially neomycin) 1
  • Fungal co-infection (otomycosis) 1, 5
  • Incorrect diagnosis (CSOM, necrotizing otitis externa) 1, 6

Special Considerations for High-Risk Patients

If the Patient Has Diabetes or Is Immunocompromised

• Monitor carefully for necrotizing (malignant) otitis externa—persistent severe pain, granulation tissue, or cranial nerve involvement requires urgent ENT referral and prolonged parenteral antibiotics 6
• Consider systemic antibiotics even for seemingly uncomplicated cases 1, 6
• Higher susceptibility to fungal infections—if white fuzzy exudate with pruritus is present, treat with topical antifungals (clotrimazole 1% solution 2-3 times daily for 7-10 days) and thorough debridement 1, 5

Critical Pitfalls to Avoid

• Prescribing oral antibiotics for uncomplicated AOE—20-40% of patients inappropriately receive them, achieving only 30-67% cure rates versus 77-96% with topical therapy 1
• Using ototoxic preparations when tympanic membrane integrity is compromised 1
• Skipping aural toilet before drop administration—medication cannot penetrate debris 1
• Irrigating the ear canal in diabetic or immunocompromised patients—this can precipitate necrotizing otitis externa 1, 6
• Missing fungal infections, especially in diabetic patients or those who fail to respond to antibacterial therapy 1, 5

Patient Instructions

• Keep the ear dry during treatment—cover the canal with an earplug or petroleum jelly-coated cotton before showering 1
• Avoid swimming and water exposure until infection resolves 1
• Do not insert cotton swabs or any objects into the ear canal 1
• Have someone else administer the drops if possible—only 40% of patients self-administer correctly 1
• Warm the bottle in hands for 1-2 minutes, lie with affected ear upward, fill the canal completely, maintain position for 3-5 minutes, and apply gentle tragal pumping 1
• Complete the full 7-day course even if symptoms resolve early 1
• Return for reassessment if symptoms don't improve within 48-72 hours or persist beyond 2 weeks 1