John C. Angus, DVM, Diplomate ACVD, Southern Arizona Veterinary Specialists, Tucson, Arizona.

Otitis externa is a clinically significant problem in 10% to 20% of the cat and dog population. There is usually an underlying problem, such as atopy, food allergy, or ectoparasites. Pseudomonas aeruginosa, although not the most common bacterial cause, is often the most frustrating to manage because of severity of the inflammatory response, unpredictable antimicrobial susceptibility patterns, and frequent treatment failure. There are several steps to diagnosis, and specific therapy for the primary disease is necessary for successful treatment. Anesthetized and deep ear flush is a valuable diagnostic and therapeutic tool for Pseudomonas infection. Topical medications are used after ear cleaning. Some agents are available as veterinary products, and some are mixtures prepared in the clinic. Veterinary products include Zymox, which has a triple enzyme formulation that is very well tolerated by patients, even if they have ulceration (the author recommends this if the patient is in too much pain to tolerate anything else), and Baytril Otic, which contains both enrofloxacin and sulfadiazine and seems to work best if there is a lot of debris in the ear canal. Use of systemic antibiotics is controversial, but if used, long-term treatment (6 to 12 weeks) is recommended. Pain management is appropriate. NSAIDs provide good analgesia but cannot be used with steroids.

COMMENTARY: Ear disease is frustrating, especially if the primary disease is not recognized. This overview provides many recommendations on how to diagnose the primary cause as well as how to manage the otitis. Another resource is the chapter by Dr. John Angus in Small Animal Dermatology Secrets (Campbell KL, ed. Philadelphia: Hanley & Belfus, 2004).