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Evaluation of the Patient with Otitis Externa
Diseases of the Ear Canal
0195-5616/88 $0.00 + .20
Evaluation of the Patient with Otitis Externa
Edmund]. Rosser, Jr., DVM*
THE IMPORTANCE OF AN ACCURATE HISTORY AND ITS PROPER UTILIZATION
The importance of a complete history cannot be overemphasized when evaluating the patient with otitis externa. This is especially true when chronic disease is present. The ultimate goal is to identify the primary problem or underlying cause of the recurrent otitis externa, and it is the historic development of the disease that most frequently gives us clues to the source of the problem. This should include a general history as well as a dermatologic history utilizing a dermatologic history questionnaire (Table 1). Specifically, the history may reveal the following: 1. The patient is a regular swimmer. 2. Evidence of a metabolic or endocrine problem such as hypothyroidism or a reproductive hormone abnormality. 3. Recent exposure of the patient to other dogs and cats (for example, humane society, boarding kennel), suggesting the possibility of a contagious disease such as otoacariasis, scabies, or dermatophytosis. 4. The presence of pruritus on areas of the body other than the ear that are compatible with pruritic skin diseases such as atopy, flea bite allergic dermatitis, food hypersensitivity, allergic contact dermatitis, or scabies. 5. Medications used previously in the ear canal may have caused irritation and inflammation, suggesting an allergic or irritant reaction to the topical medication itself. 6. Familial problems associated with that breed, including stenotic ear *Diplomate, American College of Veterinary Dermatology; Assistant Professor of Dermatology, Department of Small Animal Clinical Sciences, Veterinary Clinical Center, Michigan State University College of Veterinary Medicine, East Lansing, Michigan Veterinary Clinics of North America: Small Animal Practice-Vol. 18, No. 4, July 1988
765
766
EDMUND
J.
ROSSER, JR.
canals, presence of excessive hair in the ear canal, or excessive production of cerumen. 7. A history of recurrent infections elsewhere on or in the body such as a pyoderma or lower urinary tract infection. This leads one to consider the various diseases affecting immune function as well as a possible primary immunodeficiency. 8. The ear problem is present only on a seasonal basis such as during warm weather, suggesting an underlying disease such as atopy or flea bite allergic dermatitis. 9. The ear problem requires management and treatment on a yearround basis, and diseases such as a food hypersensitivity, scabies, or primary production of excessive cerumen should be considered. The preceding examples illustrate some of the more common conditions associated with chronic or recurrent otitis externa, and these underlying problems would probably not be pursued without taking the time to collect a thorough history. It should be emphasized that the primary cause of chronic otitis externa is rarely due to the bacteria and/or fungi found on cytology. These organisms are usually opportunists that further aggravate the condition, invariably complicating the primary or underlying disease. THE PHYSICAL EXAMINATION
General Physical Examination When evaluating the patient with the complaint of otitis externa, we often concentrate entirely on the affected area and overlook the importance of a complete physical examination. A thorough physical examination may reveal the presence of a localized or generalized lymphadenopathy (reactive lymph nodes versus lymphosarcoma), gynecomastia or pseudocyesis (possible ovarian imbalance), testicular abnormality (Sertoli cell or interstitial cell tumor, male feminizing syndrome), or concurrent conjunctivitis 1 (suggesting an allergic component to the disease).
Dermatologic Examination The external ear canal is lined by an extension of the integument from the surface toward the tympanum, and is therefore susceptible to the same changes caused by diseases affecting the skin elsewhere on the body. Examination of the skin may reveal evidence of erythema, scales, crusts, papules, excoriations, post-traumatic alopecia, or post-inflammatory hyperpigmentation. The following primary problems should be considered depending on the distribution pattern of the above lesions: l. Atopy affects the ears and the facial, interdigital, inguinal, and axillary regions in various combinations. 2. Food hypersensitivity affects the ears, the perianal and perineal regions, or virtually any area on the body. 3. Scabies affects the ears, elbows, hocks, ventral abdomen, and thorax. 4. Allergic contact dermatitis affects the contact areas of the body (feet, inguinal and axillary regions, and occasionally the ears).
EVALUATION OF THE PATIENT WITH OTITIS EXTERNA
767
Table 1. Dermatologic History Questionnaire 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.
15. 16. 17. 18. 19.
20. 21. 22.
How long has your pet had a skin problem? Age of pet when obtained? Age when skin problem started? Where on the body did the problem start? What did it look like initially? If your pet is scratching did you notice the itching or the skin lesions first? How has it spread or changed? Does the skin condition seem better or worse during any particular season? Which one? Do other pets in your household have skin problems? Do any relatives of your pet have skin problems? Which ones? Do any people in your household have skin problems? Do you use any flea control products? Which ones? How often? Do you bathe your pet? Which products? How often? If your pet is female: Are there irregular or abnormal heat cycles? Has she ever been pregnant or had false pregnancies? Has she been spayed? What age? If your pet is male: Does he have a normal interest in females? Has he been neutered? Is there any condition or environment that makes the skin problem noticeably worse? Has your pet experienced vomiting, changes of stool character, or disagreement with certain foods? Has your pet ever seemed to be ill from his/her skin disease? (depressed, fever, not eating, and so on) Please indicate if you have noticed any of the following: Scratching, biting, licking? Rubbing face on floor or furniture? Scratching at ears, rubbing ears, shaking head? Dry skin or coat? Greasy skin or coat? Scaly skin (dandruff), crusts on skin? Reddening of skin, pimples, bumps on skin? Oozing sores, open bleeding sores? Hair loss? Darkening or lightening of the skin? Thickening of the skin? Fleas? List any medications your pet has received for the condition including shampoos, lotions, ointments, dips, pills, capsules, injections, and so on (now and previously). Have any of these helped? If so, which ones? Are there any thoughts you have relating to the skin disease? What do you think may be the cause of the skin problem?
Additional diseases and their dermatologic findings include the following: 1. Endocrine diseases may include a dull, dry haircoat, a diffuse thinning of the haircoat, change of haircoat color, nonreactive symmetric alopecia with or without hyperpigmentation, seborrheic changes, or recurrent pyodermas. 2. Idiopathic familial seborrheic disorder includes the presence of ceruminous otitis externa with or without concurrent seborrheic changes on the skin in certain breeds (Cocker Spaniels, for example). 3. Autoimmune skin diseases include the presence of pustular, vesicular, bullous, erosive, or ulcerative lesions in the external ear
768
EDMUND J. ROSSER, JR.
Table 2. Otic Examination Diameter of the ear canal: Evaluate for the presence of an anatomically stenotic ear canal versus a decrease in the diameter from chronic inflammation and subsequent hypertrophy and proliferative changes. Presence of excessive hair in the external ear canal. Degree of erythema. Character of the otic discharge: Cerumen versus exudation. Indicate the color and amount present. Ulcerations and their severity. Presence of ear mites. Presence of foreign bodies or abnormal growths. Appearance of the tympanum: Intact versus rupture (and its degree); discoloration or bulging.
canal, on mucous membranes or mucocutaneous junctions, or anywhere on the skin. Whenever skin lesions are present in a patient with otitis externa, the dermatologic examination often needs to include skin scrapings (to rule out scabies or demodicosis) and a fungal culture (to rule out dermatophytosis). The preceding diagnoses include some of the more common underlying diseases found in patients with otitis externa that are associated with generalized skin disease (see the article "Otitis Externa: A Multifactorial Disease"). 3--,5 It is important to note, however, that any of the above diseases are capable of presenting with lesions that only affect the pinna and external ear canal. Otic Examination The pinna and skin around the base of the ear should be examined first. The presence of crusts on the margins of the pinnae might suggest scabies or a primary or secondary seborrheic change. The presence of diffuse pinnal erythema suggests an underlying allergic disease. The external ear canals should be palpated carefully from the exterior for any evidence of fibrosis or calcification of tissues around the external ear canal. When these changes are present, they indicate a chronic, irreversible problem with a poor prognosis for a medical cure. When performing an otoscopic examination, one should always examine both ears, even if unilateral otitis externa is suspected. 1· 3 The normal ear should be examined first, and abnormalities are often found on otoscopic examination that are overshadowed by the overt disease in the opposite ear. When both ears are affected, the less affected and less painful ear should be examined first. The otoscope head is changed before examination of the other ear to prevent unnecessary transfer of pathogenic organisms. If the patient is in too much pain to permit inspection of both external ear canals to the point of visualization of each tympanum, the procedure should be performed under sedation or general anesthesia. The abnormalities found should be noted for each ear (Table 2) and entered in the patient's record. This allows the examiner to monitor accurately the progress of the
EYALUATION OF THE PATIENT WITH OTITIS EXTERNA
769
condition on subsequent examinations, which are imperative in cases of chronic otitis externa. Many authors 1• 3 · 4 advocate using the color and odor of the discharge present in the external ear canal as a crude indication of the pathogenic organisms present. I find this method inaccurate (especially in cases of mixed infections) and distasteful, and recommend at this point in the otic examination that samples of the discharge be taken carefully utilizing a cotton swab. A portion of the discharge should be placed on a microscope slide and mixed with mineral oil for examination for ear mites. The other portion shol!ld be placed on a slide for staining and cytologic evaluation (see the article "Cytologic Evaluation of Otic Exudates"). To complete the otic examination, the external ear canal should be cleaned (see the article "Medical Management of Otitis Externa") and inspected after the cerumen and/or exudate has been removed. Occasionally, the external ear canal cannot be examined and cleaned satisfactorily (usually due to proliferative changes), and the patient must be sent home on a therapeutic regimen including a ceruminolytic agent and appropriate antimicrobial and anti-inflammatory medications (see the articles "Otopharmacology" and "Medical Management of Otitis Externa"). Ototoxic and irritating preparations should be avoided, and the patient should be rechecked in approximately 5 days to complete the otic examination. The treatment protocol is then modified as necessary.
CYTOLOGIC EVALUATION OF SMEARS VERSUS FUNGAL AND BACTERIAL CULTURE AND SENSITIVITY TESTING The most valuable technique for evaluation of pathogenic organisms in a patient with otitis externa is cytologic examination of otic exudates (see the article "Cytologic Evaluation of Otic Exudates"). Yeast organisms are easily recognized with cytologic smears, which is a rapid and inexpensive "in office" technique. One simply cannot justify the cost and delay of a fungal culture to identifY specifically whether or not the yeast is Candida or Malassezia when the principles of treatment for yeast infection are the same for both organisms (see the articles "Otopharmacology" and "Medical ~anagement of Otitis Externa"). When bacterial pathogens are present on cytologic examination, it is usually sufficient to identifY whether they are coccal organisms or rods. An appropriate topical antibiotic solution is chosen that is effective against the cocci and/or rods known to be pathogens in cases of otitis externa (see the articles "Cytologic Evaluation of Otic Exudates," "Otopharmacology," and "Medical Management of Otitis Externa"). When culture is performed on an otic exudate, a pure growth of an organism such as Pseudorrwnas may be found. However, the cytologic examination may reveal primarily cocci and yeasts. This happens because very few Pseudomonas organisms are required to overgrow a bacterial culture plate in vitro, and is not an indication of the true population of pathogens in the external ear canal. It is also important to realize that the sensitivity pattern revealed in a bacterial culture is not very useful for selection of topical medications. The
770
EDMUND
J. RossER, ]R.
sensitivity given is based on the minimal inhibitory concentration of systemic antibiotic. The antibiotic must gain access to the organism via perfusion from the blood. This has little relevance to topical therapy, and the results of sensitivity testing may actually distract the veterinarian from using an antibiotic that would be very effective if applied directly on the organism. Lastly, antibiotics used in topical therapy, such as neomycin and polymyxin B, are not included in sensitivity testing.
CLINICAL INTERPRETATION OF INFORMATION FROM A BIOPSY OF THE EXTERNAL EAR CANAL The value of histopathologic evaluation of tissue submitted from the external ear canal is often overlooked by veterinarians (see the article "Pathologic Changes in Otitis Externa"). In many instances, the biopsy may give a specific diagnosis; such is the case with polyps, neoplasia, and some of the autoimmune skin diseases that affect the external ear canal. When a specific answer is not forthcoming, the information given is often still quite useful. The pattern of inflammation may be suggestive of an allergic response and lead to the further pursuit of diseases such as atopy or food hypersensitivity. From a prognostic standpoint, the biopsy may reveal changes associated with chronic otitis externa, including dermal thickening and fibrosis, dilation and rupture of apocrine glands with a subsequent foreign body and pyogranulomatous inflammatory response, and calcification of auricular cartilage and the dermal collagen. 2 These changes are often irreversible and self-perpetuating, regardless of the initial cause of the disease. From a prognostic standpoint, therefore, this patient's ear problem can be controlled at best and may benefit from surgical intervention (see the articles "Surgical Management of Otitis Externa" and "Preventive Ear Care").
ANCILLARY AIDS FOR EVALUATION OF THE PATIENT WITH OTITIS EXTERNA The Hemogram, Serum Chemistry Profile, and Urinalysis
The major value of these tests is for screening the patient for evidence of a metabolic disease. In patients with chronic otitis externa, however, the most common abnormalities found are consistent with iatrogenic hyperadrenocorticism from the chronic use of topical and/or systemic corticosteroids. These changes may include a stress leukogram, elevated alkaline phosphatase, low blood urea nitrogen, hyperglycemia, mild to moderate glycosuria, hyposthenuria, and evidence of lower urinary tract infection. The presence of iatrogenic hyperadrenocorticism can result in a decreased resistance to infection and delayed wound healing, which counteracts the therapeutic goals. This is one more indication to approach the patient's problem aggressively by identifying the primary cause of the disease.
EVALUATION OF THE PATIENT WITH OTITIS EXTERNA
771
Specific Endocrine Tests When iatrogenic hyperadrenocorticism, hypothyroidism, or reproductive hormone imbalances are suspected based on history, physical examination, hemogram, serum chemistry profile, and urinalysis, appropriate follow-up tests should be performed. These include the ACTH response test, measurement of thyroid hormone levels, and measurement of reproductive hormone levels (estradiol, progesterone, and testosterone). Allergy Testing A primary allergic disease is usually suggested by abnormalities found on the history, physical examination, and biopsy. The following is a list of the allergic diseases that may affect the pinna and external ear canal and the tests of choice to detect them. l. Atopy: Intradermal skin testing for inhaled allergens. 2. Food hypersensitivity: Home-cooked hypoallergenic diet trials of at least 30 days' duration. 3. Allergic contact dermatitis: Patch testing with samples of contact items from the patient's environment. 4. Flea bite allergic dermatitis: Intradermal skin testing with flea antigen. Evaluation of the Immune System When a primary deficiency of the immune system is present, infections other than chronic otitis externa are usually present. These may include a superficial to deep pyoderma, lower urinary tract infection, or respiratory infection. The proper function of the cell-mediated immune system is an important component in the resistance of the body to recurrent infection. Specifically, a decreased function ofT lymphocytes may be important in the patient with recurrent infections. 5 If a patient repeatedly has an absolute lymphopenia (less than 1000 per J.Ll), one should suspect a deficiency in the cell-mediated immune response. At that point, the problem can be more specifically identified utilizing a procedure to evaluate lymphocyte function (mitogen stimulation test or in vitro lymphocyte blastogenesis test). If cellmediated immune dysfunction is present, the patient may benefit from the addition of a systemic immunostimulant to the treatment regimen. Radiography Radiographic examination should be performed whenever concurrent otitis media is suspected. The radiographs may indicate the presence of fluid densities, lytic lesions, or calcification in the osseous bulla. In addition, the radiographs may demonstrate the presence and severity of calcification secondary to chronic inflammation surrounding the external ear canal. REFERENCES l. August JR: Evaluation of the patient with otitis externa. Derm Rep 5:1, 1986 2. Dunstan RW: Personal communication, 1988 3. Fox SM, Woody BJ: Ear care in companion animals. Special Series. Vet Med 81:601, 1986
772
EDMUND
J.
ROSSER, }R.
4. Griffin CE: Otitis externa. Compend Cantin Ed Pract Vet 3:741, 1981 5. Griffin CE, Rosenkrantz WS, Tarvin G: Diseases of the external ear and pinna. In Morgan RV (ed): Handbook of Small Animal Practice. New York, Churchill Livingstone, 1988, pp 937-942 6. Rosser EJ: The use of Staphage Lysate in the treatment of refractory or recurrent pyodermas. In Proceedings of the Annual Meeting of the American Academy of Veterinary Dermatology, 1982 Department of Small Animal Clinical Sciences Veterinary Clinical Center College of Veterinary Medicine Michigan State University East Lansing, Michigan 48824-1314
0195-5616/88 $0.00 + .20
Evaluation of the Patient with Otitis Externa
Edmund]. Rosser, Jr., DVM*
THE IMPORTANCE OF AN ACCURATE HISTORY AND ITS PROPER UTILIZATION
The importance of a complete history cannot be overemphasized when evaluating the patient with otitis externa. This is especially true when chronic disease is present. The ultimate goal is to identify the primary problem or underlying cause of the recurrent otitis externa, and it is the historic development of the disease that most frequently gives us clues to the source of the problem. This should include a general history as well as a dermatologic history utilizing a dermatologic history questionnaire (Table 1). Specifically, the history may reveal the following: 1. The patient is a regular swimmer. 2. Evidence of a metabolic or endocrine problem such as hypothyroidism or a reproductive hormone abnormality. 3. Recent exposure of the patient to other dogs and cats (for example, humane society, boarding kennel), suggesting the possibility of a contagious disease such as otoacariasis, scabies, or dermatophytosis. 4. The presence of pruritus on areas of the body other than the ear that are compatible with pruritic skin diseases such as atopy, flea bite allergic dermatitis, food hypersensitivity, allergic contact dermatitis, or scabies. 5. Medications used previously in the ear canal may have caused irritation and inflammation, suggesting an allergic or irritant reaction to the topical medication itself. 6. Familial problems associated with that breed, including stenotic ear *Diplomate, American College of Veterinary Dermatology; Assistant Professor of Dermatology, Department of Small Animal Clinical Sciences, Veterinary Clinical Center, Michigan State University College of Veterinary Medicine, East Lansing, Michigan Veterinary Clinics of North America: Small Animal Practice-Vol. 18, No. 4, July 1988
765
766
EDMUND
J.
ROSSER, JR.
canals, presence of excessive hair in the ear canal, or excessive production of cerumen. 7. A history of recurrent infections elsewhere on or in the body such as a pyoderma or lower urinary tract infection. This leads one to consider the various diseases affecting immune function as well as a possible primary immunodeficiency. 8. The ear problem is present only on a seasonal basis such as during warm weather, suggesting an underlying disease such as atopy or flea bite allergic dermatitis. 9. The ear problem requires management and treatment on a yearround basis, and diseases such as a food hypersensitivity, scabies, or primary production of excessive cerumen should be considered. The preceding examples illustrate some of the more common conditions associated with chronic or recurrent otitis externa, and these underlying problems would probably not be pursued without taking the time to collect a thorough history. It should be emphasized that the primary cause of chronic otitis externa is rarely due to the bacteria and/or fungi found on cytology. These organisms are usually opportunists that further aggravate the condition, invariably complicating the primary or underlying disease. THE PHYSICAL EXAMINATION
General Physical Examination When evaluating the patient with the complaint of otitis externa, we often concentrate entirely on the affected area and overlook the importance of a complete physical examination. A thorough physical examination may reveal the presence of a localized or generalized lymphadenopathy (reactive lymph nodes versus lymphosarcoma), gynecomastia or pseudocyesis (possible ovarian imbalance), testicular abnormality (Sertoli cell or interstitial cell tumor, male feminizing syndrome), or concurrent conjunctivitis 1 (suggesting an allergic component to the disease).
Dermatologic Examination The external ear canal is lined by an extension of the integument from the surface toward the tympanum, and is therefore susceptible to the same changes caused by diseases affecting the skin elsewhere on the body. Examination of the skin may reveal evidence of erythema, scales, crusts, papules, excoriations, post-traumatic alopecia, or post-inflammatory hyperpigmentation. The following primary problems should be considered depending on the distribution pattern of the above lesions: l. Atopy affects the ears and the facial, interdigital, inguinal, and axillary regions in various combinations. 2. Food hypersensitivity affects the ears, the perianal and perineal regions, or virtually any area on the body. 3. Scabies affects the ears, elbows, hocks, ventral abdomen, and thorax. 4. Allergic contact dermatitis affects the contact areas of the body (feet, inguinal and axillary regions, and occasionally the ears).
EVALUATION OF THE PATIENT WITH OTITIS EXTERNA
767
Table 1. Dermatologic History Questionnaire 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.
15. 16. 17. 18. 19.
20. 21. 22.
How long has your pet had a skin problem? Age of pet when obtained? Age when skin problem started? Where on the body did the problem start? What did it look like initially? If your pet is scratching did you notice the itching or the skin lesions first? How has it spread or changed? Does the skin condition seem better or worse during any particular season? Which one? Do other pets in your household have skin problems? Do any relatives of your pet have skin problems? Which ones? Do any people in your household have skin problems? Do you use any flea control products? Which ones? How often? Do you bathe your pet? Which products? How often? If your pet is female: Are there irregular or abnormal heat cycles? Has she ever been pregnant or had false pregnancies? Has she been spayed? What age? If your pet is male: Does he have a normal interest in females? Has he been neutered? Is there any condition or environment that makes the skin problem noticeably worse? Has your pet experienced vomiting, changes of stool character, or disagreement with certain foods? Has your pet ever seemed to be ill from his/her skin disease? (depressed, fever, not eating, and so on) Please indicate if you have noticed any of the following: Scratching, biting, licking? Rubbing face on floor or furniture? Scratching at ears, rubbing ears, shaking head? Dry skin or coat? Greasy skin or coat? Scaly skin (dandruff), crusts on skin? Reddening of skin, pimples, bumps on skin? Oozing sores, open bleeding sores? Hair loss? Darkening or lightening of the skin? Thickening of the skin? Fleas? List any medications your pet has received for the condition including shampoos, lotions, ointments, dips, pills, capsules, injections, and so on (now and previously). Have any of these helped? If so, which ones? Are there any thoughts you have relating to the skin disease? What do you think may be the cause of the skin problem?
Additional diseases and their dermatologic findings include the following: 1. Endocrine diseases may include a dull, dry haircoat, a diffuse thinning of the haircoat, change of haircoat color, nonreactive symmetric alopecia with or without hyperpigmentation, seborrheic changes, or recurrent pyodermas. 2. Idiopathic familial seborrheic disorder includes the presence of ceruminous otitis externa with or without concurrent seborrheic changes on the skin in certain breeds (Cocker Spaniels, for example). 3. Autoimmune skin diseases include the presence of pustular, vesicular, bullous, erosive, or ulcerative lesions in the external ear
768
EDMUND J. ROSSER, JR.
Table 2. Otic Examination Diameter of the ear canal: Evaluate for the presence of an anatomically stenotic ear canal versus a decrease in the diameter from chronic inflammation and subsequent hypertrophy and proliferative changes. Presence of excessive hair in the external ear canal. Degree of erythema. Character of the otic discharge: Cerumen versus exudation. Indicate the color and amount present. Ulcerations and their severity. Presence of ear mites. Presence of foreign bodies or abnormal growths. Appearance of the tympanum: Intact versus rupture (and its degree); discoloration or bulging.
canal, on mucous membranes or mucocutaneous junctions, or anywhere on the skin. Whenever skin lesions are present in a patient with otitis externa, the dermatologic examination often needs to include skin scrapings (to rule out scabies or demodicosis) and a fungal culture (to rule out dermatophytosis). The preceding diagnoses include some of the more common underlying diseases found in patients with otitis externa that are associated with generalized skin disease (see the article "Otitis Externa: A Multifactorial Disease"). 3--,5 It is important to note, however, that any of the above diseases are capable of presenting with lesions that only affect the pinna and external ear canal. Otic Examination The pinna and skin around the base of the ear should be examined first. The presence of crusts on the margins of the pinnae might suggest scabies or a primary or secondary seborrheic change. The presence of diffuse pinnal erythema suggests an underlying allergic disease. The external ear canals should be palpated carefully from the exterior for any evidence of fibrosis or calcification of tissues around the external ear canal. When these changes are present, they indicate a chronic, irreversible problem with a poor prognosis for a medical cure. When performing an otoscopic examination, one should always examine both ears, even if unilateral otitis externa is suspected. 1· 3 The normal ear should be examined first, and abnormalities are often found on otoscopic examination that are overshadowed by the overt disease in the opposite ear. When both ears are affected, the less affected and less painful ear should be examined first. The otoscope head is changed before examination of the other ear to prevent unnecessary transfer of pathogenic organisms. If the patient is in too much pain to permit inspection of both external ear canals to the point of visualization of each tympanum, the procedure should be performed under sedation or general anesthesia. The abnormalities found should be noted for each ear (Table 2) and entered in the patient's record. This allows the examiner to monitor accurately the progress of the
EYALUATION OF THE PATIENT WITH OTITIS EXTERNA
769
condition on subsequent examinations, which are imperative in cases of chronic otitis externa. Many authors 1• 3 · 4 advocate using the color and odor of the discharge present in the external ear canal as a crude indication of the pathogenic organisms present. I find this method inaccurate (especially in cases of mixed infections) and distasteful, and recommend at this point in the otic examination that samples of the discharge be taken carefully utilizing a cotton swab. A portion of the discharge should be placed on a microscope slide and mixed with mineral oil for examination for ear mites. The other portion shol!ld be placed on a slide for staining and cytologic evaluation (see the article "Cytologic Evaluation of Otic Exudates"). To complete the otic examination, the external ear canal should be cleaned (see the article "Medical Management of Otitis Externa") and inspected after the cerumen and/or exudate has been removed. Occasionally, the external ear canal cannot be examined and cleaned satisfactorily (usually due to proliferative changes), and the patient must be sent home on a therapeutic regimen including a ceruminolytic agent and appropriate antimicrobial and anti-inflammatory medications (see the articles "Otopharmacology" and "Medical Management of Otitis Externa"). Ototoxic and irritating preparations should be avoided, and the patient should be rechecked in approximately 5 days to complete the otic examination. The treatment protocol is then modified as necessary.
CYTOLOGIC EVALUATION OF SMEARS VERSUS FUNGAL AND BACTERIAL CULTURE AND SENSITIVITY TESTING The most valuable technique for evaluation of pathogenic organisms in a patient with otitis externa is cytologic examination of otic exudates (see the article "Cytologic Evaluation of Otic Exudates"). Yeast organisms are easily recognized with cytologic smears, which is a rapid and inexpensive "in office" technique. One simply cannot justify the cost and delay of a fungal culture to identifY specifically whether or not the yeast is Candida or Malassezia when the principles of treatment for yeast infection are the same for both organisms (see the articles "Otopharmacology" and "Medical ~anagement of Otitis Externa"). When bacterial pathogens are present on cytologic examination, it is usually sufficient to identifY whether they are coccal organisms or rods. An appropriate topical antibiotic solution is chosen that is effective against the cocci and/or rods known to be pathogens in cases of otitis externa (see the articles "Cytologic Evaluation of Otic Exudates," "Otopharmacology," and "Medical Management of Otitis Externa"). When culture is performed on an otic exudate, a pure growth of an organism such as Pseudorrwnas may be found. However, the cytologic examination may reveal primarily cocci and yeasts. This happens because very few Pseudomonas organisms are required to overgrow a bacterial culture plate in vitro, and is not an indication of the true population of pathogens in the external ear canal. It is also important to realize that the sensitivity pattern revealed in a bacterial culture is not very useful for selection of topical medications. The
770
EDMUND
J. RossER, ]R.
sensitivity given is based on the minimal inhibitory concentration of systemic antibiotic. The antibiotic must gain access to the organism via perfusion from the blood. This has little relevance to topical therapy, and the results of sensitivity testing may actually distract the veterinarian from using an antibiotic that would be very effective if applied directly on the organism. Lastly, antibiotics used in topical therapy, such as neomycin and polymyxin B, are not included in sensitivity testing.
CLINICAL INTERPRETATION OF INFORMATION FROM A BIOPSY OF THE EXTERNAL EAR CANAL The value of histopathologic evaluation of tissue submitted from the external ear canal is often overlooked by veterinarians (see the article "Pathologic Changes in Otitis Externa"). In many instances, the biopsy may give a specific diagnosis; such is the case with polyps, neoplasia, and some of the autoimmune skin diseases that affect the external ear canal. When a specific answer is not forthcoming, the information given is often still quite useful. The pattern of inflammation may be suggestive of an allergic response and lead to the further pursuit of diseases such as atopy or food hypersensitivity. From a prognostic standpoint, the biopsy may reveal changes associated with chronic otitis externa, including dermal thickening and fibrosis, dilation and rupture of apocrine glands with a subsequent foreign body and pyogranulomatous inflammatory response, and calcification of auricular cartilage and the dermal collagen. 2 These changes are often irreversible and self-perpetuating, regardless of the initial cause of the disease. From a prognostic standpoint, therefore, this patient's ear problem can be controlled at best and may benefit from surgical intervention (see the articles "Surgical Management of Otitis Externa" and "Preventive Ear Care").
ANCILLARY AIDS FOR EVALUATION OF THE PATIENT WITH OTITIS EXTERNA The Hemogram, Serum Chemistry Profile, and Urinalysis
The major value of these tests is for screening the patient for evidence of a metabolic disease. In patients with chronic otitis externa, however, the most common abnormalities found are consistent with iatrogenic hyperadrenocorticism from the chronic use of topical and/or systemic corticosteroids. These changes may include a stress leukogram, elevated alkaline phosphatase, low blood urea nitrogen, hyperglycemia, mild to moderate glycosuria, hyposthenuria, and evidence of lower urinary tract infection. The presence of iatrogenic hyperadrenocorticism can result in a decreased resistance to infection and delayed wound healing, which counteracts the therapeutic goals. This is one more indication to approach the patient's problem aggressively by identifying the primary cause of the disease.
EVALUATION OF THE PATIENT WITH OTITIS EXTERNA
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Specific Endocrine Tests When iatrogenic hyperadrenocorticism, hypothyroidism, or reproductive hormone imbalances are suspected based on history, physical examination, hemogram, serum chemistry profile, and urinalysis, appropriate follow-up tests should be performed. These include the ACTH response test, measurement of thyroid hormone levels, and measurement of reproductive hormone levels (estradiol, progesterone, and testosterone). Allergy Testing A primary allergic disease is usually suggested by abnormalities found on the history, physical examination, and biopsy. The following is a list of the allergic diseases that may affect the pinna and external ear canal and the tests of choice to detect them. l. Atopy: Intradermal skin testing for inhaled allergens. 2. Food hypersensitivity: Home-cooked hypoallergenic diet trials of at least 30 days' duration. 3. Allergic contact dermatitis: Patch testing with samples of contact items from the patient's environment. 4. Flea bite allergic dermatitis: Intradermal skin testing with flea antigen. Evaluation of the Immune System When a primary deficiency of the immune system is present, infections other than chronic otitis externa are usually present. These may include a superficial to deep pyoderma, lower urinary tract infection, or respiratory infection. The proper function of the cell-mediated immune system is an important component in the resistance of the body to recurrent infection. Specifically, a decreased function ofT lymphocytes may be important in the patient with recurrent infections. 5 If a patient repeatedly has an absolute lymphopenia (less than 1000 per J.Ll), one should suspect a deficiency in the cell-mediated immune response. At that point, the problem can be more specifically identified utilizing a procedure to evaluate lymphocyte function (mitogen stimulation test or in vitro lymphocyte blastogenesis test). If cellmediated immune dysfunction is present, the patient may benefit from the addition of a systemic immunostimulant to the treatment regimen. Radiography Radiographic examination should be performed whenever concurrent otitis media is suspected. The radiographs may indicate the presence of fluid densities, lytic lesions, or calcification in the osseous bulla. In addition, the radiographs may demonstrate the presence and severity of calcification secondary to chronic inflammation surrounding the external ear canal. REFERENCES l. August JR: Evaluation of the patient with otitis externa. Derm Rep 5:1, 1986 2. Dunstan RW: Personal communication, 1988 3. Fox SM, Woody BJ: Ear care in companion animals. Special Series. Vet Med 81:601, 1986
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4. Griffin CE: Otitis externa. Compend Cantin Ed Pract Vet 3:741, 1981 5. Griffin CE, Rosenkrantz WS, Tarvin G: Diseases of the external ear and pinna. In Morgan RV (ed): Handbook of Small Animal Practice. New York, Churchill Livingstone, 1988, pp 937-942 6. Rosser EJ: The use of Staphage Lysate in the treatment of refractory or recurrent pyodermas. In Proceedings of the Annual Meeting of the American Academy of Veterinary Dermatology, 1982 Department of Small Animal Clinical Sciences Veterinary Clinical Center College of Veterinary Medicine Michigan State University East Lansing, Michigan 48824-1314