Principles of Therapy for Otitis

Chapter 108

Principles of Therapy for Otitis

This chapter emphasizes the general principles essential to the successful diagnosis, treatment, and management of otitis. Additional information regarding specific therapeutic methods for otitis is found in other chapters within this section.

Primary Causes and Predisposing and Perpetuating Factors of Otitis

The initial goal in the management of otitis is determining the primary cause of the otic disease and controlling any predisposing and perpetuating factors. The primary cause of otitis externa must be diagnosed, treated, and controlled or the condition is likely to become chronic or recurrent, which makes the ear disease much more difficult to manage. In a retrospective study of 100 dogs with acute (37%) or chronic (63%) otitis externa, the most common primary cause of the otitis was underlying allergic disease. This may include cutaneous adverse food reaction (CAFR), atopic dermatitis, or both. This point was emphasized in another retrospective study of 130 dogs in which 10 of 16 dogs (62.5%) diagnosed with CAFR had bilateral otitis externa, a prevalence that was significantly higher than in study dogs without CAFR. In addition to allergic diseases, other primary causes of otitis externa include parasitic diseases (e.g., Otodectes cynotis infestation), keratinization disorders, juvenile cellulitis, foreign bodies, autoimmune disease, endocrine disease, otic neoplasms, and nasopharyngeal polyps.

Predisposing factors facilitate inflammation of the ear by altering the microenvironment of the ear canal, allowing for establishment of secondary infections. Once these factors are identified, as many as possible should be eliminated. Predisposing factors include otic conformation (e.g., stenotic ear canals, pendulous pinna), excessive moisture (e.g., swimming), and injury due to treatment effects. The latter can include hair plucking, trauma from the use of cotton-tipped applicators, improper antibiotic use, and application of irritant solutions.

Perpetuating factors sustain and aggravate the inflammatory process, preventing resolution of or even worsening the otitis. Bacterial and yeast infections are the most common perpetuating factors. But undoubtedly in chronic recurrent otitis externa, there also will be progressive pathologic changes such as hyperplasia or stenosis in the ear canal as well as a high probability of a concurrent otitis media. The otic examination allows assessment of the degree of hyperplasia, erythema, ulceration, and stenosis present in the ears. It is also important to palpate the ear canals to identify thickening or even calcification of the canals.

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Jul 18, 2016 | Posted by in PHARMACOLOGY, TOXICOLOGY & THERAPEUTICS | Comments Off on Principles of Therapy for Otitis

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