PEER REVIEWED Externa Series: Part 1 DIAGNOSIS OF Ashley Bourgeois, DVm Wayne rosenkrantz, DVm, Diplomate ACVD Animal Dermatology Clinic, tustin, California

This article—the first of a 2-part series—discusses diagnosis of otitis externa. Topical therapy for treatment of otitis externa will be discussed in the November/December 2014 issue of Today’s Veterinary Practice (tvpjournal.com).

titis externa is a prevalent complaint in patients ary causes, such as bacterial or yeast overgrowth, typically presented to small animal practices. This inflam- become chronic issues. matory disease of the external canal and/or Opinna can have an acute or chronic presentation. Perpetuating Factors Management of otitis externa depends on identifying and Perpetuating factors are changes in anatomy and physi- treating predisposing and perpetuating factors, as well as ology of the ear that occur in response to otitis externa. primary and secondary causes (Table 1). They are most commonly seen in chronic cases and are not disease specific. These factors can accentuate develop- FACTORS & CAUSES ment of secondary infections by providing environments Predisposing Factors and microscopic niches that favor their persistence. Predisposing factors alone do not cause otitis externa, but In severe cases, perpetuating factors can ultimately pre- increase risk for development and persistence of chronic vent the resolution of otitis externa by leading to irrevers- infection. These factors work in conjunction with primary ible changes of the . They are the most common or secondary causes, allowing otitis externa to become a reason that otitis externa fails to respond to medical ther- significant problem. apy and, ultimately, requires surgical intervention.

Primary Causes DIAGNOSTIC TESTING Primary causes of otitis externa are the inciting agent or Diagnostic testing begins with a minimum database of: etiology that directly damages the ear canal’s epithelium, • Detailed history resulting in subsequent inflammation. To prevent recur- • Physical examination rent episodes of otitis externa, it is critical that a primary • Ear canal cytology. cause be diagnosed and managed. Cytology Secondary Causes Cytologic examination of ear canal discharge provides a Secondary causes of otitis externa do not create pathol- brief overview of the aural environment, providing a foun- ogy in a healthy ear; instead, they incite disease in dation for therapeutic decisions and advanced diagnos- affected by a primary cause or predisposing factor. If the tics.1,2 It is also the primary tool in identifying bacterial or inciting cause or factor is inadequately controlled, second- yeast overgrowth.

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TABLE 1. Common Predisposing Factors, Primary & Secondary Causes, & Perpetuating Factors of Otitis Externa PERPETUATING PREDISPOSING FACTORS PRIMARY CAUSES SECONDARY CAUSES FACTORS • abnormal external ear canal • atopic dermatitis (Figures 1 • Yeast overgrowth • Ear canal/pinna fibrosis and pinna conformation, and 2) (Figures 1 and 2) and stenosis (Figure 7) such as congenital stenosis • food allergy (Figures 3 and 4) • bacterial overgrowth • Calcification of tissues • Excessive moisture within • Epithelialization disorders, such (Figures 3 through 6) • neoplasia (polyps, ear canal as seborrhea (Figures 5 and 6) tumors, cysts) (Figure 8) • adverse effects from pre- • Metabolic disorders, such as vious treatments, such as hypothyroidism topical reactions • neoplasia

1 2

7

Figure 1. Atopic dermatitis with Malassezia otitis externa Figure 2. Malassezia cytology from dog in Figure 1

3 4

8

Figure 3. Adverse food reaction with mixed bacterial otitis externa Figure 4. Mixed bacterial cytology from dog in Figure 3

5 6

Figure 7. Chronic proliferative otitis externa due to atopic dermatitis Figure 8. Ceruminous gland cyst causing obstructive otitis externa Figure 5. Seborrhea with Pseudomonas otitis externa in cocker spaniel Figure 6. Pseudomonas cytology from dog in Figure 5

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Initial cytology should be performed prior to bacterial culture and sensitivity (C/S) testing because bacterial C/S & External Ear Canal Bacterial is not recommended if only yeast overgrowth is noted. See Spectrums In Practice: External Ear Canal Cytology for a stepwise The spectrum of bacteria and their sensitivity pat- approach to cytologic sample collection. terns seen in the middle ear (which is lined with cili- ated columnar epithelium) and external ear canal (which is lined with epidermis) may differ due to In Practice: External Ear Canal Cytology variations in cellular composition. In a study by 1. Carefully insert an applicator tip in the ear canal Cole and colleagues, different strains of Pseudo- and, near the junction of the vertical and horizon- monas species, based on sensitivity pattern, were tal canals, collect material for cytologic examina- cultured from each location.3 Other studies have tion. shown different strains of a bacterial species from 2. Collect deeper, and generally more representa- a single sampling site.4,5 tive, samples by passing an ear loop or pediatric feeding tube through an otoscopic cone. 3. Transfer samples onto a glass slide, heat fix, and DIAGNOSTIC IMAGING stain with Diff-Quik. Otoscopy 4. When examining samples under the microscope, note the: In addition to detailed history, physical examination, and • number of bacteria and yeast per oil immer- ear canal cytology, otoscopy is part of a diagnostic mini- sion field (100×) mum database, and can diagnose several conditions that • Presence or absence of inflammatory cells. create deeper ear canal disease (Table 2). must have a strong light and power source, com- bined with at least 10× magnification that allows focusing within the normal length of the ear canal. Avoid using a bat- Culture & Sensitivity tery-operated that has significantly lost power and Indications for C/S include: light, which results in a diminished view of the deep ear canal. • Suppurative inflammation (including that with bacterial Either a traditional diagnostic otoscope or surgical oto- rods, cocci, or no visible organisms) revealed during ini- scope head may be used. The benefits of surgical otoscopes tial cytology include, in certain cases: • Lack of response to appropriate topical and systemic • Enhanced manipulation and angulation within the ear antibiotic therapy canal • Systemic therapy required for or deeper, • Passage of tubes or other instruments into the ear canal soft-tissue infections of ear canal with concurrent visualization. • Resistant strains of bacteria suspected. Resistant bacteria should be suspected if: • History of chronic topical therapy Table 2. Diagnostic Imaging for Ear Disease • Rods observed on cytology IMAGING EAR DISEASE/CONDITION • Bacteria persistent on cytologic examination despite MODALITY EVALUATED appropriate therapy (ie, suspect methicillin-resistant Otoscopy Identifies: Staphylococcus pseudintermedius). • Canal proliferation, masses, foreign Ideally, topical or systemic antibiotic therapy should be dis- bodies continued 3 to 5 days prior to acquisition of culture samples. • ruptured tympanic membrane • Changes in integrity and density of Laboratory Submission tympanic membrane When preparing the sample for submission, include any • large bulging pars flaccida, suggesting pertinent information regarding the organisms seen on primary secretory otitis media (seen cytology and a representative cytology slide. in cavalier King Charles spaniels)8 In addition, if rods are observed on cytology—suggest- Radiography Detects bony involvement of bullae; ing the presence of Pseudomonas species—additional anti- has limited value in soft tissue chang- biotic sensitivities should be requested with bacterial cul- es, especially in acute cases Computed Aids in differentiation of bony lesions ture, including: axial in the bullae from soft tissue reactions • Polymyxin B tomography • Ticarcillin Magnetic Aids in visualizing middle and inner • Third-generation cephalosporin. resonance ear and detects presence of fluids, Once the laboratory report is in hand, in addition to sus- imaging such as endolymph within the cochlea ceptibility, it is important to review the reported minimum and semicircular canals inhibitory concentration, which helps direct the choice or Ultrasonography Detects fluid within the tympanic bullae dose of antibiotic required.

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In Practice: Ear Cleaning & Flushing Table 3. Additional Equipment for Diagnostic or 1. Patient restraint is often required for thorough oto- Therapeutic Procedures scopic examination; sedation or general anesthe- sia may be required. Use EQUIPMENT COLLECTION OF SAMPLES General anesthesia is preferred for more ag- Break up concretions • Ear curettes or loops (espe- gressive flushing procedures, as placement of and remove small cially useful for material an endotracheal tube avoids aspiration of fluids pieces of cerumen, located near the tympanic (ie, those that may pass through a ruptured tym- debris, or foreign bodies membrane) panic membrane into the middle ear, through the Collect large samples • Large forceps that can pass auditory canal, and into the posterior pharynx). for histopathology through the handheld oto- For greatest safety, inflate the endotracheal tube scope cuff and pack the pharynx with gauze, which is Collect smaller • Narrow alligator or biopsy removed prior to anesthetic recovery. samples for forceps histopathology • Smaller diameter forceps that can pass through the 2. For client education and medical documentation, FVEO port take an initial photograph prior to cleaning and Collect cytology • Long, thin needles that can then one after the procedure for comparison. samples from middle be passed through the oto- 3. Use a handheld otoscope to determine the sever- ear scope cone and reach the ity of disease and type and amount of debris in deep ear canal (eg, 22-gauge the external ear canal. spinal tap needles) 4. Use a combination of cleaning techniques to facil- itate more rapid and effective removal of debris FLUSHING OF EAR CANALS from the canals (Table 3): Initial flushing of ear • Bulb syringes and cleaning • Utilize forceps and ear curettes through a hand- canals solutions held otoscope head to remove larger debris. Flushing of ear canals • Tomcat catheters or infant • After large debris is removed, typically a bulb feeding tubes and/or tube is used for flushing, with or without Deep flushing through • Feeding tubes trimmed down ceruminolytics (see Common Ceruminolytics). handheld otoscope or to allow better manual con- • Consider FVEO for deeper cleaning and evalua- FVEO trol but long enough to reach tion of the ear canal. Deeper therapeutic flush- the deep ear canal (eg, 5F, es can be especially beneficial in cases of otitis 8F, and 10F) externa with biofilm-producing organisms, such Aggressive, deep ear • Intravenous tubing and as Pseudomonas species ( ), in which Figure 6 flushing procedures 3-way stopcocks 9 manual removal of debris is essential. Utilize that allow consistent • FVEO units with continuous a 5F feeding tube, cut to the appropriate size fluid availability flushing and suction options for the patient, for deep flushing and suctioning through the FVEO port. THERAPEUTIC PROCEDURES 5. If necessary, aspirate a sample of debris from the Intralesional injections • Long, thin needles (see deeper ear canal, as well as the middle ear if the Myringotomy Collection of Samples) tympanic membrane is ruptured, for both cyto- Myringotomy • Tomcat catheters, if the tip is logic examination and C/S testing. Use the FVEO cut at a sharp angle port for passage of biopsy forceps or an appropri- ately modified ear curette. If you encounter any problems related to use of FVEO, refer to Table 4. Table 4. Common Problems with FVEO Use & Possible Solutions

Common Ceruminolytics PROBLEM POSSIBLE SOLUTION Ceruminolytics help break down larger pieces of waxy debris, such as ceruminoliths, and are gen- Lens fogging Remove the probe and clean tip tle and soothing to the epithelium of the ear canal. Use defogging solution • Squalene Warm probe tip in water • Urea peroxide Obstruction of lens Wipe the lens with a cotton ball • Carbamide peroxide with debris soaked in 70% isopropyl alcohol • Hexamethyl tetracosane or a defogging solution • Dioctyl sodium/calcium sulfosuccinate Decreased magnifica- Flush with water or saline during • triethanolamine polypeptide elite condensate tion & visualization use

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Various sizes of otoscopic cones are required to properly of a primary cause and any perpetuating and predisposing examine ear canals based on patient size. factors is essential for complete resolution and prevention of recurrence of otitis externa. Fiberoptic Video-Enhanced Otoscopy Identification of infectious organisms through cytology Advancement of fiberoptics, improved lighting, and min- is an essential first step for initial treatment. Thorough iaturization of video cameras, combined with rigid endos- ear cleaning and flushing coupled with appropriate anti- copy, has led to development of fiberoptic video-enhanced microbials, based on C/S when necessary, enhance treat- otoscopy (FVEO). FVEO, despite its expense to purchase ment success. n and maintain, is extremely beneficial for improved diag- nostics, therapy, and client education. C/S = culture and sensitivity; CT = computed tomography; The camera within the fiberoptic tip significantly magni- FVEO = fiberoptic video-enhanced otoscopy; MRI = fies and improves visualization of the ear canal. FVEO also magnetic resonance imaging facilitates permanent recordings via picture or video of the ear canal—including debris, foreign bodies, and masses— References which can be shared with clients and other veterinarians. 1. Ginel PF, Lucena R, Rodriguez J, Ortega J. A semiquantitative cytological examination of normal and pathological samples from the external ear canal Compared with handheld otoscopy, FVEO allows: of dogs and cats. Vet Dermatol 2002; 13(3):151-156. • Thorough flushing with water or saline, providing better 2. Tater K, Scott D, Miller W, Erb H. The cytology of the external ear canal visualization and magnification in the normal dog and cat. J Vet Med A Physiol Pathol Clin Med 2003; • 50(7):370-374. Observation of fine details, such as small tears of the 3. Cole L, Kwochka K, Kowalski J, Hillier A. Microbial flora and antimicrobial tympanic membrane, consequently recognized as air susceptibility patterns of isolated pathogens from the horizontal ear canal bubbles extruding from the middle ear cavity through and middle ear in dogs with otitis media. JAVMA 1998; 212(4):534-538. the tympanic membrane. 4. Schick A, Angus JC, Coyner K. Variability of laboratory identification and antibiotic susceptibility reporting of Pseudomonas spp. isolates from dogs with chronic otitis externa. Vet Dermatol 2007; 18(2):120-126. Additional Imaging 5. Graham-Mize C, Rosser E Jr. Comparison of microbial isolates and In chronic otitis cases, the following imaging techniques susceptibility patterns from the external ear canal of dogs with otitis externa. JAAHA 2004; 40(2):102-108. may be helpful diagnostic tools. Table 2 lists these addi- 6. Rohleder J, Jones J, Duncan R, et al. Comparative performance of tional imaging modalities as well as the types of condi- radiography and computed tomography in the diagnosis of middle ear tions they can diagnose and evaluate. However, the cost disease in 31 dogs. Vet Radiol Ultrasound 2006; 47(1):45-52. 7. Doust R, King A, Hammond G, et al. Assessment of middle ear disease in and availability of these diagnostics may make them pro- the dog: A comparison of diagnostic imaging modalities. J Small Anim Pract hibitive for some clients. 2007; 48(4):188-192. Computed tomography (CT) and magnetic resonance 8. Cole LK. Primary secretory otitis media in Cavalier King Charles Spaniels. Vet Clin Small Anim Pract N Am 2012; 42(6):1137-1142. imaging (MRI) have been shown to be more reliable and 9. Pye C, Yu A, Weese J. Evaluation of biofilm production by Pseudomonas 6 accurate than radiography. CT is most commonly used aeruginosa from canine ears and the impact of biofilm on antimicrobial due to efficiency and expense; however, if soft tissue mass- susceptibility in vitro. Vet Dermatol 2013; 24(4):446-449. es or vestibular disease is suspected, MRI is more accurate. In one study, diagnosis of otitis media by CT was found to have an 86% sensitivity and 89% specificity compared with the gold standard of histopathologic diagnosis.6 Ultrasound has been used for the detection of fluid with- in the tympanic bulla, with 80% to 100% sensitivity and 74% to 100% specificity compared with the gold standard of CT.7

EAR CLEANING & FLUSHING Ashley Bourgeois, DVM, recently Cleaning and flushing the ears is critical for: completed her residency at Animal Der- • Proper visualization and examination of ear canal matology Clinic in Tustin, California. She • Determination of disease extent has served as education chair with the • Indications for additional diagnostics and case manage- American College of Veterinary Derma- ment tology (ACVD). She received her DVM from University of Missouri and com- • Determination of disease resolution. pleted a small animal internship at Purdue University. See In Practice: Ear Cleaning & Flushing (page 18) for a stepwise description of appropriate cleaning and flushing. Wayne Rosenkrantz, DVM, Dip- Typically, patients can be maintained with once to twice lomate ACVD, is co-founder of Ani- weekly flushing, but frequency of flushing should be deter- mal Dermatology Clinic. He is a clini- mined on a case-by-case basis. cal instructor for Western Veterinary Medicine College and an instructor for SUMMARY European School of Advanced Veteri- nary Studies. He is past president of the Otitis externa is a multifactorial inflammatory disease of ACVD and a board member of the World Association for the ear canals and pinnae that may become chronic. Chro- Veterinary Dermatology. He received his DVM from Uni- nicity is usually due to inadequate control of the primary versity of California—Davis. cause or the presence of a perpetuating factor. Detection

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