A Practical Approach to Diagnosing and Managing Ear Disease in Dogs
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SERIES EDITOR Craig E. Griffin, DVM, DACVD Animal Dermatology Clinic, San Diego, California SERIES EDITOR Wayne S. Rosenkrantz, DVM, DACVD Animal Dermatology Clinic, Tustin, California A Practical Approach to Diagnosing and Managing Ear Disease in Dogs ❯❯ Paul Bloom, DVM, DACVD, DAVBP (Canine and Feline) Allergy, Skin and Ear Clinic For Pets Livonia, Michigan ntire books have been written on the subject of canine ear mendations for primary causes (e.g., parasiti- Edisease. Rather than attempt to present all the available cidal treatment, food trial) is beyond the scope of this article. information here, I am providing an overview of how I diag- Predisposing factors must also be addressed nose and manage ear disease in dogs. It is critical to appreciate if possible. Although predisposing factors do that ear disease is only a clinical problem (no more specific not cause ear disease, they increase the risk than pruritus)1 and that steps must be taken to prevent otitis for its development and may make success- ful treatment more difficult.1–4 Anatomic fac- externa from progressing to proliferative otitis. BOX 1 summa- tors (such as the long pendulous ears of basset rizes step-by-step approaches to specific clinical scenarios. hounds), excessive moisture in the ears (from swimming), and iatrogenic trauma (plucking Identification of Primary Causes and hairs from the ear canals) are examples of pre- At a Glance Predisposing and Perpetuating Factors disposing factors. Identification and treatment of the primary Perpetuating factors do not cause otitis Identification of (underlying) cause(s) of ear disease are impor- externa, but clinicians often consider them to Primary Causes and tant to determining the appropriate manage- be the reasons for disease when the problem Predisposing and ment approach.1–4 The most common primary is that the primary cause has not been identi- Perpetuating Factors causes of otitis externa are: fied or treated. Even if the primary cause is Page E1 eliminated, perpetuating factors may cause Specific Scenarios: Hypersensitivities (atopy and cutaneous ad - the ear disease to continue. Examples of per- Step by Step verse food reaction); unilateral ear disease petuating factors include: Page E2 may be the only clinical sign of an underly- Diagnosis ing hypersensitivity Bacteria Page E3 Parasites (Otodectes and Demodex spp) Yeast (Malassezia pachydermatis) T r e a t m e n t Foreign bodies (e.g., grass awns) Progressive pathologic changes Page E4 Autoimmune or immune-mediated diseases Otitis media (e.g., pemphigus foliaceus) Undertreatment (dose or duration)—a very common problem a Dr. Bloom discloses that he If the primary cause of otitis externa is not has received financial support from Novartis Animal Health addressed, the ear disease will likely recur; These factors must also be identified and and Pfizer Animal Health. however, a discussion of the treatment recom- treated or corrected. The treatment section of CompendiumVet.com | May 2009 | Compendium: Continuing Education for Veterinarians® E1 ©Copyright 2009 Veterinary Learning Systems. This document is used for internal purposes only. Reprinting or posting on an external website without written permission from VLS is a violation of copyright laws. BOX 1 Specific Scenarios: Step by Step Acute and/or Infrequent Otitis Externa TABLE 1 Patient Factors and Therapy Ascertain whether this is a first-time at Initial Presentation for Acute Otitis episode, a recurrence, or an unresolved previous infection (acute-on-chronic Patient Factor Therapy otitis). Unfortunately, differentiating between Only yeast present Azole (for miconazole, add 3 mL of dexamethasone sodium phosphate [4 mg/mL concentration] to 30 mL recurrence and unresolved infection is often of miconazole) difficult because of the lack of good follow- Cocci present ± rods Neomycin or gentamicin up, which emphasizes the importance of performing follow-up examinations on all Only rods present TrisEDTA + gentamicin otitis externa cases. The absence of clinical Dog is in pain Add systemic glucocorticoids ± analgesics (tramadol, 2–5 mg/kg bid–tid and/or acetaminophen with codeine signs is not synonymous with resolution [codeine, 2 mg/kg bid–tid]); do not mix systemic of disease. For dogs experiencing their first glucocorticoids and NSAIDs. episode of otitis, educate the owners about the Tympanic membrane not Add topical fluocinolone acetonide + dimethyl sulfoxide possible primary cause(s) and predisposing initially visualized (because of + oral glucocorticoids (prednisone, 0.50–0.75 mg/kg PO and perpetuating factors and outline the ear canal swelling) q12h for 10–14 days); recheck dog in 10–14 days workups that may be necessary. Eliminate easily diagnosed primary TABLE 2 causes (e.g., foreign bodies, parasites, Patient Factors and Therapy masses) and perform a thorough otoscopic at Recheck for Acute Otitis examination, including evaluation of the Patient Factor Therapy tympanic membrane. Tympanic membrane visible and Discontinue prednisone; continue other therapy Diagnose and treat secondary infection(s) swelling resolved and inflammation. My first line of treatment Tympanic membrane not visible Perform ear lavage, using a standard otoscope or, for inflammation is a topical glucocorticoid but swelling resolved preferably, a fiber-enhanced video otoscope with patient under general anesthesia ointment; I base other treatment choices on the patient factors outlined in TABLE 1. Tympanic membrane not visible Continue prednisone for another 10–14 days and recheck and swelling not resolved If the ear canals are still narrowed at recheck, Recheck the patient after 7–14 days of consider referring patient to a dermatologist before treatment. This is critical in the proper contemplating ear ablation management of ear disease (TABLE 2). Continue treatment for 7–14 days beyond resolution of clinical signs. TABLE 3 Patient Factors and Therapy at Presentation for Chronic Otitis Chronic Otitis (Recurrent and/or Patient Factor Therapy Unresolved) Only yeast present Depending on what products have already been used, switch to 1% clotrimazole, 1% miconazole, or Follow the steps outlined for acute otitis compounded 2% ketoconazole lotion externa. Add topical steroids either by mixing dexamethasone Identify and treat the primary cause, any sodium phosphate to a final concentration of 0.1% predisposing factors (if possible), and with current product or by concurrent use of a product containing fluocinolone acetonide perpetuating factors. If drops are dispensed Cleanse ear Treatment (TABLE 3) should last for a minimum of 30 days. In patients with severe ear inflammation, use a mild cleanser Cocci ± rods TrisEDTA (with or without 0.15% chlorhexidine) + either Chronic Pseudomonas Infections gentamicin or polymyxin B (depending on which antibiotics have already been used). Note: I rarely use These infections are especially challenging, and fluoroquinolones in these cases unless the infection a discussion of the required therapy is beyond fails to respond to therapy. This means a follow-up the scope of this article. examination is essential. E2 Compendium: Continuing Education for Veterinarians® | May 2009 | CompendiumVet.com this article generally addresses perpetuating To avoid missing abnormalities, the otic factors; however, if the primary cause is not examination should be performed systemati- identified and managed, treatment of the per- cally, beginning with the pinna. Any alope- petuating cause will not eliminate ear disease. cia, erythema, ulceration, crusting, scaling, or swelling should be noted and the ear canals Diagnosis palpated to identify pain, calcification, or History thickening. External ear disease is a form of skin disease, Because the presence of pain can limit and, as with any skin problem, a detailed his- proper evaluation of the ear canal, the dog tory must be gathered. History taking for an should be evaluated for pain and sedated as otic problem is similar to that for any general needed before the otoscopic examination is medicine problem. Two key points to discuss performed. The presence, degree, and loca- with the pet owner are the age of the dog tion of inflammation, ulceration, and prolifera- when ear disease first appeared and whether tive changes of the ear canals should be noted. the dog has been treated for skin or ear dis- Likewise, it should be noted whether the tym- ease in the past. panic membrane is visible and, if so, whether Owners should be questioned about the it appears normal. A ruptured or abnormal first episode of ear disease in the dog’s life (bulging, necrotic, or thickened) tympanic and not just when the current episode was first membrane may indicate the presence of otitis noticed. Determining the dog’s age at onset media2,3,5; however, the tympanic membrane helps narrow the possible primary causes of may thicken in cases of chronic otitis externa otitis externa. For example, if the first epi- without the presence of otitis media. If the QuickNotes sode developed when the dog was between tympanic membrane cannot be visualized, an 6 months and 5 years of age, atopic dermati- attempt should be made to identify the reason. If the primary cause tis or cutaneous adverse food reactions would Potential causes include a ruptured membrane, of ear disease is not be a likely cause; however, if the dog was swelling or debris in the ear canal, or a false identified and man- older than 7 years when it first developed oti- middle ear (a condition in which the tympanic aged, treatment of tis