What are the diagnostic criteria for Otitis Externa (inflammation of the external ear canal)?

From the Guidelines

Otitis externa is diagnosed through a combination of clinical history and physical examination, with diagnostic criteria including ear canal edema, erythema, discharge, debris, and tenderness, as outlined in the clinical practice guideline by the American Academy of Otolaryngology—Head and Neck Surgery Foundation 1. The diagnosis is made when a patient presents with ear pain, often accompanied by itching, discharge, and sometimes hearing loss, along with visible inflammation of the external ear canal.

• During examination, the healthcare provider will use an otoscope to visualize the ear canal, looking for redness, swelling, discharge, and debris.
• Gentle manipulation of the tragus or pinna typically elicits pain in otitis externa, which helps differentiate it from otitis media.
• The tympanic membrane should be assessed for integrity, though it may be difficult to visualize if significant canal edema is present. In severe cases, fever and regional lymphadenopathy may be present.
• Laboratory tests are generally unnecessary unless the infection appears complicated or fails to respond to initial treatment.
• Cultures may be obtained in cases of recurrent or resistant infections to identify specific pathogens, particularly if fungal infection is suspected, as fungal involvement is distinctly uncommon in primary AOE but may be more common in chronic otitis externa or after treatment of AOE with topical or systemic antibiotics 1. Imaging studies are rarely needed but may be considered if complications such as malignant otitis externa are suspected, particularly in diabetic or immunocompromised patients, as they are susceptible to otomycosis and necrotizing otitis externa, which may present similar to AOE but require different management 1.

From the Research

Otitis Externa Diagnosis

• Otitis externa is usually treated empirically with topical neomycin/polymyxin B/hydrocortisone 2
• The predominant pathogens associated with this infection are Pseudomonas aeruginosa and Staphylococcus aureus 2, 3
• Acute otitis externa presents with the rapid onset of ear canal inflammation, resulting in otalgia, itching, canal edema, canal erythema, and otorrhea, and often occurs following swimming or minor trauma from inappropriate cleaning 3
• Tenderness with movement of the tragus or pinna is a classic finding 3

Diagnostic Procedures

• Otoscopic evaluation of the external ear canal and tympanic membrane is the first diagnostic procedure that should be performed in animals presented with otitis externa 4
• The purpose of the otoscopic examination is to address the otitis by evaluating the condition of the ear, looking for any masses or foreign bodies; noting the presence, consistency, and color of any exudate; and evaluating the patency of the tympanic membrane 4

Treatment Options

• Topical antimicrobials or antibiotics such as acetic acid, aminoglycosides, polymyxin B, and quinolones are the treatment of choice in uncomplicated cases 3
• Neomycin/polymyxin B/hydrocortisone preparations are a reasonable first-line therapy when the tympanic membrane is intact 3
• Ciprofloxacin otic solution 0.2% was found to be noninferior to polymyxin B-neomycin-hydrocortisone in the treatment of acute diffuse otitis externa 5
• The clinical cure rate for patients with baseline cultures showing P. aeruginosa was 87.5% in the ciprofloxacin group and 78.6% in the polymyxin B-neomycin-hydrocortisone group 5