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Ear Cytology 1093

collected from the mycelial surface by gently various stages of the same pathologic process Allergy testing:
applying the sticky side of clear acetate tape or multiple problems, with emphasis on • Food allergy is most reliably diagnosed based
VetBooks.ir then pressed onto a glass slide over a drop of • Punch biopsy specimens (usually 6 mm) can • Atopic dermatitis is most reliably diagnosed
primary lesions if possible (e.g., pustules,
to the aerial surface. The tape with sample is
on an elimination food trial followed by a
provocation food trial (p. 345).
vesicles).
methylene blue or lactophenol cotton blue
stain and examined under microscope for
2% lidocaine per site injected SQ beneath
characteristic macroconidia. be obtained under local anesthesia (1 mL of by intradermal skin testing (or serology
testing) (p. 91).
Bacterial culture and sensitivity (C&S) (p. the specimen; do not exceed 1 mL/5 kg of
1333) body weight). If a pustule or other small Alternatives and Their
• Due to a recent increase of methicillin- lesion is selected, it should be centered in Relative Merits
resistant Staphylococcus pseudintermedius, the biopsy specimen. The biopsy punch Therapeutic trials (e.g., antiparasitic, antimicro-
C&S are performed much more commonly should be rotated in only one direction bial) can be valuable in establishing a diagnosis
in canine pyoderma. to minimize shearing artifact. Handle the and are frequently performed in veterinary
• The Culturette swabs are used for collecting specimen carefully. The forceps should dermatology. For example, therapeutic trials
moist exudates from pustules under crusts grasp the hairs of the biopsy sample or its with an acaricidal agent are indicated when
or epidermal collarettes. deepest surface (e.g., subcutis), never the sarcoptic mange is suspected but skin scrapings Procedures and Procedures and Techniques Techniques
• Otic cultures are generally performed when core of the biopsy sample. The specimen are negative.
rods and neutrophils are seen on cytologic must be put rapidly (<2 minutes) in 10%
examination. neutral buffered formalin. Skin biopsy punch SUGGESTED READING
Skin biopsy: sites can be sutured with 1-2 interrupted Miller WH Jr, et al: Muller & Kirk’s Small animal
• The biopsy technique selected (punch biopsy, sutures. dermatology, ed 7, St. Louis, 2013, Saunders, pp
wedge biopsy, excisional biopsy) varies • Skin biopsies, along with a detailed history, 78–95.
according to the type of lesions. animal description, biopsy sites, +/− photos,
• Site selection is crucial. Choose several should be submitted to a veterinary AUTHOR: Manon Paradis, DMV, MVSc, DACVD
EDITORS: Leah A. Cohn, DVM, PhD, DACVIM; Mark S.
representative lesions that may represent dermatopathologist. Thompson, DVM, DABVP

Ear Cytology

Difficulty level: ♦ • Microscope for evaluation of slide wax and allow penetration of the sample
• Seldom requires sedation by the stain.
Synonym • The slide is stained using the modified Wright
Otic cytology Anticipated Time stain (Diff-Quik).
15 minutes, including staining and viewing • Dry, crumbly, black exudates are typical of
Overview and Goal ear mite infestation; another swab should
Ear cytology is a screening test to assess for Preparation: Important be rolled into mineral oil and then covered
microorganisms and the cellular character of the Checkpoints with a coverslip to examine for mites.
ear canal. It is an essential part of the examina- • Assistant to restrain the patient Examination of the slides:
tion of the ear canal in patients with suspected • Premark a slide so as to identify which side • Mineral oil preps are examined under low
otitis externa (p. 728) and otitis media. is up. power (4× objective to orient the viewer and
10× to identify mites)
Indications Possible Complications and • Stained slides are examined under low
• Ear cytology should be performed on all Common Errors to Avoid power to orient the viewer and find areas
patients with visible ear canal inflammation • Inadequate sample from not sampling deep of high cellularity/organisms. The slide is
or exudate. into the vertical ear canal then examined under higher power (40×
• Mineral oil preps of dark exudates may • Difficulty in sampling a painful or aggressive objective) to identify organisms such as
identify Otodectes or Demodex mites. patient. An experienced assistant should Malassezia pachydermatis, bacterial rods or
• Follow-up ear cytology is useful to assess provide restraint rather than the pet owner. cocci, fungi such as Candida or Aspergillus,
response to therapy. • Ear canal too swollen or occluded to allow and neutrophils. Squamous cells and keratin
sampling are normally found in ear cytologies but may
Contraindications be seen in increased numbers with inflam-
Patients that do not allow sampling of the Procedure mation and in dog breeds predisposed to
ear canal with a swab due to pain-induced Collection of the sample: ceruminous otitis externa.
aggression • Debris is collected from the vertical canal
of each ear on a cotton swab. Postprocedure
Equipment, Anesthesia • The swab from the right ear is rolled on the Therapy depends on clinical presentation and
• Cotton swabs on wooden applicator sticks right side of the slide, and the swab of the interpretation of ear cytology.
long and stiff enough to allow sampling from left ear is rolled on the left side.
deep in vertical ear canal • Although heat fixing is a common practice, Alternatives and Their Relative
• Glass microscope slides studies have shown it to be unnecessary. If Merits
• ± Lighter for heat fixing the collected material is waxy, the slide may • Otodectes mites may be detected as small,
• Modified Wright stain (Diff-Quik) be heated briefly with the lighter to melt the white specks moving within the ear canal

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