Diagnosis and medical treatment of otitis externa in the dog and cat

Otitis externa is no longer viewed as an isolated disease of the ear canal, but is a syndrome that is often a reflection of underlying dermatological disease. Causes are classified as predisposing (increase the risk of otitis); primary (directly induce otitis), secondary (contribute to otitis only in an abnormal ear or in conjunction with predisposing factors) and perpetuating (result from inflammation and pathology in ear, prevent resolution of otitis). Common primary causes include foreign bodies, hypersensitivity (particularly atopy and food allergy), keratinisation disorders (most commonly primary idiopathic seborrhoea and hypothyroidism) and earmites, particularly in cats. A systematic diagnostic procedure is required to identify causes and contributing factors. This should include history, clinical examination, otoscopy and cytology in all cases and culture and sensitivity as well as otitis media assessment and biopsy in severe and recurrent cases. Ancillary tests may be required depending on the underlying cause. Treatment consists of identifying and addressing predisposing and primary factors; cleaning the ear canal; topical therapy; systemic therapy where necessary; client education; follow-up; and preventive and maintenance therapy as required.     

Aetiology of canine otitis externa: a retrospective study of 100 cases

The objective of this retrospective study was to investigate in 100 dogs with otitis externa (OE) the possible associations between signalment, history, clinical and laboratory findings and the various primary, secondary and perpetuating causative factors of ear canal inflammation. The age of the dogs ranged from 3 months to 14 years (median: 4.75 years) and they included 45 males and 55 females. Cocker spaniels, Jura des Alpes and Brittany spaniels were significantly overrepresented among dogs with OE when compared to the hospital canine population. In the majority of the cases, OE was chronic-recurrent (63%) or bilateral (93%). Allergic dermatitis (43/100 dogs), grass awns (12/100) and otoacariasis (7/100) were the most common primary causative factors; no primary factor could be incriminated in 32 cases and more than one was found in three dogs. Malassezia spp. (66/100 dogs), cocci (38/100) and rods (22/100) were the secondary causative factors, while ear canal stenosis (38/100) and tympanic membrane perforation-otitis media (25/100) were the most important perpetuating factors. Atopic dermatitis and adverse food reactions-associated OE was more common in females and dogs with a history of pruritic skin disease, while grass awn-induced OE occurred in cocker spaniels and acute cases. Tympanic membrane perforation was less frequent in atopic dermatitis and adverse food reactions-associated OE, but more common when otoscopic and ear canal cytological examination revealed the presence of grass awns and rods, respectively. Finally, cocci overgrowth was positively associated with ear canal stenosis.     

Causes of otitis externa.

Dogs with long-standing, chronic, recurrent otitis externa often represent one of the most frustrating types of problems in daily clinical practice. The important aspect of this discussion is that the clinician may be presented with a patient in which the primary chief complaint is otitis externa but a wide variety of disease processes may be causing the problem, including various combinations of the primary, predisposing, and perpetuating causes as discussed previously. The use of a thorough history and general and dermatologic physical examinations often leads the clinician to establish a systematic approach to identify the specific underlying problems. Until this is accomplished, the recurrent nature of the otitis externa will remain as a persistent problem.     

Otitis externa. A disease of multifactorial etiology

Dogs and cats with long-standing otitis externa pose a difficult diagnostic challenge for the veterinarian, because chronically affected ears usually have the same appearance regardless of the underlying cause(s). In patients with chronic otitis externa, the disease is often caused by different combinations of primary, predisposing, and perpetuating factors. The unique therapeutic needs of each patient may be determined by careful interpretation of historical and physical findings, which should be supported by ancillary diagnostic tests.     

Surgical management of 43 cases of chronic otitis externa in the dog

: Over a seven-year period, chronic otitis externa was surgically managed in 43 dogs at the University Veterinary Hospital of University College Dublin. Lateral ear canal resection (LECR) was undertaken in nine of the 43 dogs: results were unsatisfactory, with a failure of the surgery in five of eight dogs and one dog lost to follow-up. Once end-stage otitis externa, with or without otitis media, is diagnosed, total ear canal ablation and lateral bulla osteotomy (TECA/LBO) is the best treatment option. In this series, 37 of 43 dogs underwent TECA/LBO and of the 29 dogs for which follow-up results were obtained 27 (93%) had an excellent or improved outcome to surgery. Complications following all procedures were most common in cases with a concurrent dermatopathy; therefore, definitive diagnosis and medical treatment for skin and ear disease is essential.     

Diagnosis and medical treatment of otitis externa in dogs and cats

A review of otitis externa in dogs and cats is presented. Aetiology, includes primary causes: ectoparasitoses, allergic diseases, endocrine disorders, pyodermas, trauma and irritation, contact dermatitis, auto-immune skin diseases, drug eruption, keratoseborrhoeic skin disease, tumours and pseudoneoplastic lesions, as well as secondary causes: bacteria and yeasts. Clinical aspects are variable but a practical classification distinguishes two forms: erythematoceruminous otitis externa and suppurative otitis externa. Diagnosis is made in five steps which are clinical examination, direct examination of cerumen (erythematoceruminous otitis externa) or bacterial culture and sensitivity testing (suppurative otitis externa), direct impression smears, cleaning and otoscopy, and diagnosis of underlying skin disease. Medical therapy includes cleaning of the external ear canal and local therapy (acaricides, antifungal agents, antibiotics, corticosteroids, other topical agents, the appropriate selection of an optic preparation being essential). Treatment of underlying skin disease is always necessary. Otitis externa is in fact a dermatological disease complex (like pododermatitis). Although local secondary infections (bacterial and fungal) must be managed in every case, there are grounds for including otitis externa in a larger frame.     

Topical ear treatment – options,indications and limitations of current therapy

Topical otic products form an integral part of the overall management of otitis externa. With an ever increasing array of ear drops and cleaners to choose from, appropriate selection of therapy can be difficult. The investigation of all cases of otitis externa should consider primary and secondary causes and predisposing and perpetuating factors. This article considers topical therapy under these same broad headings and discusses, through literature review, the various properties of the components of the ear cleaning solutions and drops.     

Surgical Management of Rabbit Ear Disease

Clinical signs associated with otic disease in rabbits (Oryctolagus cuniculus) are very similar to those demonstrated in dogs and cats. The surgical treatment options to resolve diseases involving the rabbit ear are also comparable with those used for canine and feline species. However, there are key anatomic and physiologic differences that must be accounted for to perform proper surgical treatment on a rabbit that has been diagnosed with ear disease. This article describes the diagnostic and treatment options for otitis externa, otitis media, and otitis interna, with an emphasis on surgical procedures and the important distinctive otic features of the rabbit patient. The ventral bulla osteotomy procedure is recommended for management of otitis media in rabbits without otitis externa. In rabbits with pathology in the external ear canal and the middle ear, total ear canal ablation and lateral bulla osteotomy should be performed. This combined procedure will allow the surgeon to address pathology in both sites, with the ultimate goal of resolution of the underlying disease etiology. Lateral ear canal resection is only appropriate in rabbits with otitis externa without otitis media; however, this surgical procedure may not resolve the otitis externa. If this is a concern, a total ear canal ablation should be done because it offers a greater chance of success.     

Surgical management of otitis externa

The surgical management of otitis externa is discussed in conjunction with failed medical management, primary causes, and proper case selection. The techniques of lateral ear canal resection and vertical ear canal ablation are described in detail.     

Morphologic measurements of the external horizontal ear canal of dogs

Microscopic anatomy of the horizontal part of the external ear canal was evaluated in 24 dogs. Sixteen dogs were from breeds known to have a predisposition to otitis externa. The remaining 8 dogs were from breeds that do not have a predisposition to otitis externa. Dogs were separated into groups according to predisposition to otitis externa: group 1-predisposed dogs without otic inflammation, group 2-predisposed dogs with otic inflammation, and group 3-nonpredisposed dogs without otic inflammation. Qualitative microscopic evaluation of distribution of hair follicles revealed hair within proximal, middle, and distal regions of the horizontal ear canal in all breeds. The degree of keratinization was directly proportional to the presence of otic inflammation and was excessive in group-2 dogs. Quality of sebaceous glands within the horizontal ear canal was similar among dogs with and without otitis externa, whereas the quantity of apocrine tubular glands was significantly increased (P less than 0.05) in dogs with otitis. Quantity of apocrine tubular glands was also greater in group-1 dogs than in group-3 dogs. Thickness of the soft tissue in the external ear canal increased in direct proportion to the progression of disease and was greatest in the proximal region of the affected ear canal. Soft tissue located caudally between nonopposing ends of the annular cartilage, within the proximal region of the horizontal ear canal, contained few glands and hair follicles in dogs without otitis externa. In dogs with otitis externa, this region was infiltrated by distended apocrine tubular glands.     

Total ear canal ablation combining bulla osteotomy and curettage in dogs with chronic otitis externa and media

Ear canal ablation combining bulla osteotomy and curettage was performed on 44 dogs (n = 72 ears). Indications for the procedure included one or more of the following: chronic nonresponsive otitis externa and/or media (n = 71), tumor in the horizontal portion of the ear canal (n = 1), failed lateral ear resection (n = 11), ossified auricular cartilages secondary to chronic otitis externa (n = 22), failed previous total ear canal ablation (n = 1), and otitis interna (n = 1). In 40 dogs, the surgery was successful in alleviating all clinical signs of otitis externa and media. During the immediate postoperative period, 2 dogs died of causes unrelated to otitis. Complications related to the surgery developed in 9 of the surviving 42 dogs. Ultimately, 95% (40 of the surviving 42) of the dogs were cured by use of this procedure. Surgery successfully resolved the original problems in 97% (66 of 68) of the surgically treated ears of these dogs.     

Chronic Otitis Externa and Otitis Media Treated by Total Ear Canal Ablation and Ventral Bulla Osteotomy in Thirteen Dogs

Ventral bulla osteotomy was combined with total ear canal ablation for the treatment of chronic otitis externa and otitis media in 13 dogs (14 ears) that had been refractory to medical and surgical treatments. Resolution of disease occurred in 11 dogs (12 ears). One dog with unilateral disease underwent a second operation before achieving a good result. One dog was euthanatized for persistent unilateral disease after three surgical procedures. The recurrence of disease in these two dogs (15%) was associated with remnants of ear canal integument within the osseous horizontal canal or tympanic bulla. Facial paralysis occurred in four dogs (31%) and there were no complications in eight dogs (62%). This technique shows no advantage over lateral bulla osteotomy combined with total ear canal ablation for the treatment of chronic otitis externa and otitis media.     

Breed variations in histopathologic features of chronic severe otitis externa in dogs: 80 cases (1995-2001)

OBJECTIVE: To compare pathologic changes of the horizontal ear canal associated with chronic severe otitis externa between Cocker Spaniels and dogs of other breeds. DESIGN: Retrospective study. ANIMALS: 80 dogs with severe otitis externa that required total ear canal ablation with lateral bulla osteotomy. PROCEDURE: Medical records were reviewed for breed, sex, and age at time of surgery. Histologic specimens from the horizontal ear canal were evaluated by a single examiner for overall tissue response pattern and scored for sebaceous gland hyperplasia, ceruminous gland hyperplasia, ceruminous gland ectasia, fibrosis, pigment-laden macrophages, and osseous metaplasia. RESULTS: 48 of 80 (60%) dogs were Cocker Spaniels. Thirty-five of 48 (72.9%) Cocker Spaniels had a predominately ceruminous tissue response pattern; only 9 of 32 (28.1 %) dogs of other breeds had the same pattern. Other breeds most commonly had a pattern dominated by fibrosis (n = 13 [40.6%]); fibrosis was the predominant pattern in only 4 of 48 (8.3%) Cocker Spaniels. Discriminant analysis and K-means clustering of 4 histopathologic criteria correctly classified 75% of the dogs as Cocker Spaniels or all other breeds. CONCLUSIONS AND CLINICAL RELEVANCE: Cocker Spaniels are at increased risk for chronic severe otitis externa requiring total ear canal ablation with lateral bulla osteotomy, indicating that earlier and more aggressive management of the primary otitis externa and secondary inflammation is warranted in this breed. Cocker Spaniels with chronic severe otitis externa have distinct differences in pathologic characteristics of the horizontal ear canal, compared with other breeds.     

Effects of ear type and weather on the hospital prevalence of canine otitis externa

A retrospective study of 8975 dogs seen at 15 university veterinary medical teaching hospitals in North America (1975 to 1978) found that dogs with pendulous ears and heavy ear canal hair had significantly (P less than 0.01) more otitis externa than dogs with other ear types. Dogs with erect ears, regardless of the amount of ear canal hair, had less risk (P less than 0.01) of the disease than mongrel dogs. Direct evidence is available for the first time showing that monthly variations in ambient temperature, rainfall and relative humidity explain, to a large extent, the monthly variations in the hospital prevalence of canine otitis externa in different geographic regions.     

Chronic otitis externa with heat shock protein 70-positive intranuclear inclusion bodies in the ceruminous gland epithelium of a Chihuahua dog

A Chihuahua dog showed persistent itching in the right ear canal. Anti-inflammatory medicines and prednisolone were ineffective and total ear canal ablation was performed. Histological diagnosis was chronic otitis externa. Eosinophilic intranuclear inclusion bodies (Cowdry type A and full-type) were occasionally observed in the ceruminous gland epithelium. The inclusion bodies were negative for nucleic acid and ultrastructurally composed of fibrous structures (approximately 10 nm in width). Viral infection was initially suspected, but polymelase chain reaction tests did not detect the expected viral genes. Immunohistochemistry revealed that the inclusion bodies were positive for heat shock protein 70 (HSP70), suggesting that these bodies could be protein aggregates including HSP70. The etiology of this lesion has not been elucidated, but chronic inflammation may influence the cytoplasm-to-nuclear transportation of HSP70. To the best of our knowledge, this is the first report of canine chronic otitis externa with HSP70-positive intranuclear inclusion bodies.     

Inflammatory middle ear disease of the dog: the pathology of otitis media

Inflammation within the middle ear cavity was recognised in 62 of the ears of 42 dogs with chronic otitis externa and otitis media, after biopsy or necropsy of the middle ear. The pathological changes in the middle ear resembled those reported in other species or after the experimental induction of otitis media in dogs. Perforations in the tympanic membrane were rarely found; on the contrary, the membrane was often thickened. However, the question of whether a perforation in the tympanic membrane must occur before otitis externa can extend to otitis media was not resolved.     

Ulcerative otitis externa responsive to immunosuppressive therapy in two dogs

Two middle-aged dogs were presented with bilateral severe ulcerative otitis externa without previous history of disease or evidence of other skin disease. Based on the exclusion of microbial infection and other primary causes, histopathological findings and response to immunomodulatory treatment, a diagnosis of presumed immune-mediated ulcerative otitis externa was made in both cases. However, the two cases differed with regard to their histopathological characteristics and the course of the disease. This report indicates that primary ulcerative disease needs to be considered in cases of ulcerative otitis externa which are unresponsive to appropriate antimicrobial therapy.     

Measurement of body temperature by use of auricular thermometers versus rectal thermometers in dogs with otitis externa

OBJECTIVE: To compare measurements of body temperature obtained with auricular thermometers versus rectal thermometers in dogs with otitis externa. DESIGN: Prospective study. ANIMALS: 100 client-owned dogs: 50 with and 50 without clinical evidence of otitis externa. PROCEDURE: Dogs were evaluated for the presence of otitis externa on the basis of clinical signs, otoscopic examination, and cytologic evaluation of ear exudate. Auricular and rectal temperatures were obtained simultaneously in all dogs prior to and following ear examination. RESULTS: There was a high correlation between auricular and rectal temperatures in dogs with otitis externa both prior to and after ear manipulation. Significant differences were not detected in temperature measurements among dogs with different degrees of otitis externa. CONCLUSIONS AND CLINICAL RELEVANCE: Auricular temperature readings obtained by use of an auricular thermometer in dogs with otitis externa are accurate measurements of body temperature, compared with rectal temperature measurements. Temperature measurements are reliable before and after examination of the ear canal.     

Diagnosis and treatment of otitis media in dogs and cats.

Otitis externa/media is commonly found in dogs with chronic ear diseases and in cats with upper respiratory disease and polyps. Diagnosis of otitis media requires attention to history and clinical signs, but it also requires other methods of determining disease within the bulla. If the integrity of the eardrum cannot be determined, assume that there is middle ear disease and proceed accordingly. It is prudent to take necessary precautions to avoid the use of potentially ototoxic ear cleaners or topical medications in suspected otitis media cases. Therapeutic success is possible using systemic and topical treatment within the cleaned bulla. Referral to a dermatology specialist or a radiologist for a CT scan may be indicated in some refractory cases. Surgical intervention may be required to cure these difficult cases.     

Medical management of otitis externa

Successful medical management of otitis externa requires attention to all of the following points: 1. Diagnose and treat systemic or underlying disease(s). 2. Carefully clean and examine the entire ear canal before starting therapy. This includes removal of foreign bodies, parasites, hair, and other obstructions. 3. Apply carefully chosen topical preparations based on gross and microscopic examination. 4. Educate clients as to the causes of the otitis externa and their role in treating the disease. 5. Schedule regular follow-up examinations until the disease is completely cured. 6. Recommend preventive procedures such as drying ears after swimming, corrective surgery, and so on. 7. Use systemic treatment when indicated by chronicity of disease or the owner's inability to treat the patient.