Endoscopic examination of the external and middle ear for chronic and severe ear infections

There are few things as frustrating as dealing with a dog with either persistent or recurrent otitis externa.

In the vast majority of cases, bacteria are not the primary problem and, more specifically, the bacteria cultured from the external ear canal are probably not implicated in most chronic cases.

Undiagnosed rupture of the eardrum is the most common cause of chronic otitis externa

Even when the eardrum has healed over, most of the bacteria responsible for perpetuating the problem 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.

It is very difficult to assess the integrity of the eardrum in an infected or inflamed ear with a conventional otoscope. The light is often not strong enough to transilluminate the ear drum and when instruments are used through a conventional otoscope, the view of the examiner is often obliterated.

We have seen many cases in our clinic where it has been assumed that the ear drum is intact when in fact the membrane is either perforated or diseased.

Oto-endoscopy

The unit we use is a fiberoptic otoendoscope. The external ear canal and tympanic membrane are brightly illuminated and magnified permitting a more accurate assessment of the ear drum.

If otitis media is suspected but the tympanic membrane has healed, we can perform a myringotomy via the operating channel; collect samples of exudate from the middle ear and then flush the middle ear using suction. In many cases it is also possible to tell at an early stage if the eardrum epithelial growth centre has been compromised, and whether surgery is indicated rather than medical approaches.

The endoscope is also invaluable for collecting biopsy material from polyps and neoplasia in the external and middle ear and while the patient is anaesthetised the ears can be flushed, foreign objects, debris or parasites may be retrieved with grasping forceps.

With an attachable dual port adaptor, suction and saline may be used simultaneously to completely clean the ear.

Determining underlying causes

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.

Only when the correct underlying cause has been identified and managed will the condition be readily controlled.

If you have a patient with recurrent bacterial or yeast ear infections that you suspect are caused by underlying allergies then referral for allergy testing is worthwhile sooner rather than later.

Once the external ear canal has significantly narrowed from fibrous hyperplasia, medical approaches may no longer be an option.