Today's Veterinary Practice

MAY-JUN 2017

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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62 DERMATOLOGY DETAILS PEER REVIEWED usually because primary causes or perpetuating factors have not been adequately addressed. Predisposing Factors Predisposing factors alone do not cause otitis externa, but they facilitate inflammation by permitting the external ear canal microenvironment to be altered, thereby allowing pathogenic or opportunistic bacteria or yeast to become established. 1,2 In conjunction with primary or secondary causes, these factors become a significant problem. It is important to eliminate as many of these factors as possible while realizing that some, such as ear conformation, cannot be changed. Perpetuating Factors Perpetuating factors sustain and aggravate the inflammatory process and prevent resolution of, or worsen existing, otitis externa. 1,2 Once present, they accentuate or permit the development of secondary causes, such as infection, by providing favorable environments and microscopic niches. In many cases, perpetuating factors prevent the resolution of otitis externa when treatments are directed only at primary and secondary causes. These factors may be subtle at first but can develop into the most severe component of chronic ear disease. They are not disease specific and are most commonly seen in chronic cases. Perpetuating factors are the most common reasons for surgical intervention. IMPORTANT DIAGNOSTIC STEPS History A detailed and complete history is essential to help investigate the underlying cause and associated factors. Otic Examination The ear examination allows the clinician to evaluate the amount and type of exudate in the ear canals; estimate the amount of otic inflammation; identify hyperplasia (along with palpation of the horizontal and vertical ear canals), masses, and foreign bodies; and determine the status of the tympanic membrane (eg, changes in structure or rupture). These findings help in determining whether medical management or surgery (total ear canal ablation with or without bulla osteotomy) is the best treatment. If the patient's ears are painful, sedation or general anesthesia may be necessary before otoscopic examination. Regular (ie, handheld) otoscopes should have a strong light and power source. If available, fiberoptic video-enhanced otoscopy (eg, video- otoscope [ Figure 3 ]) is extremely helpful in improving diagnosis and therapy because it not only allows visualization of fine details that may not be seen with regular otoscopes but also facilitates proper flushing of the ears, determination of disease extent, and discovery of indications for additional diagnostics and treatment (eg, myringotomy, otitis media). However, because of the expense to purchase and maintain this equipment, referral to a dermatologist may be necessary. Physical Examination Performing a complete physical examination, including a detailed dermatologic examination, can help in identifying an underlying or primary cause. In patients with otitis media and/or otitis interna, concurrent neurologic abnormalities (eg, facial paralysis, nystagmus, ataxia, head tilt) may be present; therefore, a detailed neurologic examination is indicated. Otic Cytology Otic cytology establishes whether an infection is present in the ears and assists with the selection FIGURE 3. Video otoscopic examination.

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