Ear infections (otitis externa) in dogs were the most common reason for veterinary visits in 2015, according to Veterinary Pet Insurance. The second most common reason for visits was skin allergies, which is a common primary cause of otitis externa.
Otitis externa can be extremely frustrating for owners and veterinarians alike, especially in the case of chronic otitis externa. Fortunately, there are several new otic formulations available to help with infectious otitis externa and also with owner compliance. These newer medications are long-acting and applied infrequently, once a week to once every 3 weeks. They are also water soluble, which helps them penetrate deeper into the ear canal and also makes removing them easier than removing lanolin-based products if the patient experiences contact reactions.
Chronic otitis externa is usually a result of either the infection not being treated completely or the underlying cause not being addressed. With continued inflammation, the ears will progress to fibrosis and ultimately calcification. The lumen of the ear canals will also become extremely stenotic, which prevents medications from passing into the horizontal ear canal and reaching the tympanic membrane.
Advanced imaging, such as CT, can provide a large amount of information in these chronic otitis externa cases. Sometimes there is otitis media, a neoplastic tumor within the ear canal causing an obstruction, a focal stenosis and the rest of the canal is normal, and sometimes the lumen is completely nonexistent through the tympanic membrane. CT will also reveal how much calcification is present. Thus, advanced imaging is absolutely necessary in chronic otitis externa cases.
If there is significant fibrosis and stenosis without calcification, systemic corticosteroids can help to open the ear canal and reverse the changes. Unfortunately, when calcification occurs, surgery is the best option and could require complete removal of the ear canals. This surgery can be expensive, but it may help the patient feel more comfortable. It is a salvage procedure, and the patient will most likely experience hearing loss after the surgery. Unless the underlying primary factor—allergies, endocrine disease, immune-mediated diseases—is addressed, there will still be inflammation at the surgical site and complications will occur.
Some patients are not able to go through this extensive surgery for various reasons, and laser can be successful in removing the redundant tissue and help to subsequently resolve the infection.
Figure 1 (on the left) shows an external ear canal that was completely stenotic from the entrance of the external ear canal to the tympanic membrane. The owner chose not to have a total ear canal ablation with bulla osteotomy on the patient; instead, we performed multiple laser procedures to open up the ear canal, making the patient more comfortable.
The results are seen in Figure 2 (on the right) after one procedure. The underlying primary factor still needs to be addressed in these cases or the stenosis will recur. However, laser surgery through the video otoscope is a viable alternative to surgery.
Intralesional injections of triamcinolone have also been performed to decrease inflammation. The anti-fibrotic effects of triamcinolone can help decrease the changes that are seen with chronic otitis externa. This can be extremely painful though, and deep sedation is necessary for this procedure.
If the patient is not able to undergo anesthesia or sedation for either procedure, addressing the infection with routine cleaning and pulse topical therapy is the best option. This will be a lifelong therapy, but it can keep the patient more comfortable. But again, addressing the underlying primary factor is needed.
—Jason Pieper, DVM, DACVD