Tufts University School of Veterinary Medicine, Dermatology Service, Walpole, MA, USA; Bizvet, Inc., Westborough, MA, USA
©2005 Lowell Ackerman D.V.M. No portion of this material may be reproduced without the written consent of author.
There are few things as frustrating as dealing with a dog with chronically inflamed ears. They're swollen, they're painful, and owner and pet are just looking for some long-term relief. That shouldn't be to tough, but despite a plethora of ointments, drops, and flushes available, and the most expensive antibiotics money can buy (often several of them in succession), managing these cases can be a nightmare.
Importantly, antibiotics are not the sole answer. In the vast majority of cases, bacteria are not the primary problem and, more specifically, the bacteria cultured from the outer ear are probably not the ones secondarily involved in most chronic cases. Undiagnosed rupture of the eardrum is the number one cause of chronic otitis externa. Even when the eardrum has healed over, most of the bacteria responsible for keeping the problem ongoing originate from the middle ear and, in roughly 85% of cases, these are not the same bacterial species isolated from swabs of the external ear canal.
My preferred approach to dealing with chronic ears is to first examine cytology specimens taken from the external ear canal to determine the extent of involvement of bacteria, yeasts, and inflammatory cells, and then examine all aspects of the eardrum itself via otoendoscopy. The unit I use is a fiberoptic otoendoscope to actually clearly visualize the tympanum and surrounding tissues. If otitis media is suspected but the eardrum has healed over, there is an operating channel on the unit to take biopsies, or to perform a myringotomy and take samples from the middle ear. In many cases it is also possible to tell at an early stage if the eardrum epithelial growth center has been compromised, and whether surgery is indicated rather than medical approaches. Photographs can also be taken with the unit, and this is great for promoting owner compliance.
While otoendoscopy has evolved into a great tool for diagnosing ear canal problems, it is important to realize that in almost all cases there is an underlying problem (e.g., allergy, keratinization disorders, hypothyroidism, etc.) that also needs to be addressed. In almost no cases are bacteria the primary problem, so repeat cultures, and playing antibiotic roulette is rarely an effective long-term strategy. It's also worthwhile to begin the diagnostic process sooner rather than later. Once the ear canal has significantly narrowed from fibrous hyperplasia, medical approaches may no longer be an option.
There are lots of different causes for otitis and, while it may seem surprising, true bacterial causes are actually rare. While bacteria and yeast are frequent complicating factors for ear problems, the most common underlying causes are inhalant allergies, adverse food reactions, metabolic problems, and immune-mediated conditions. Only when the correct underlying cause has been identified and managed will the condition be readily controlled.
We are indeed fortunate that modern medicine has provided technology to more completely evaluate the ear canal than was previously possible. A standard otoscope works fine in people, but dogs and cats have a vertical then a horizontal ear canal, making it almost impossible to visualize the eardrum of the awake animal in most cases. Since undiagnosed rupture of the eardrum is the most common cause for chronic relapsing otitis, this was a real problem. Now otoendoscopy allows a fiberoptic endoscope to be placed in the ear canal, which provides startlingly clear images of the eardrum and surrounding tissues in dogs and cats. Why not just take swabs from the ear for bacterial cultures? Because bacteria are rarely the primary cause of the problem, and because if the eardrum is ruptured and there is a middle ear infection, the bacteria are likely to be different from that found in the outer ear canal. Antibiotics can act as a Band-Aid for the problem, but in the vast majority of cases they provide only temporary relief. Once they are discontinued, if the underlying problem has not been corrected, the ear problem is likely to recur.