224 (25)

Diagnostic tests

Once a diagnosis of ECO or SO has been madę, it is essential to look for predisposing, primary, amplifying and / or aggravating factors, involved in the development of clinical signs (Table 22 : 1)^l'⁸ ". A diagnosis limited to “otitis” merely describes inflammation of the ear and does not give any indication of prognosis, treatment or likely recurrence. Carrying out appropriate diagnostic tests will optimise the chances of making an aetiological diagnosis³ (Table 22 : 2).

Table 22 : 2 : Diagnostic approach to otitis extema

EXAMINATION FROM A DISTANCE CLOSE-UP EXAMINATION POSSIBLEINITIAL AUROSCOPIC EXAMINATION

: ■ vw,w •„ mw.'-

Otodectes cynotis, Demodex cati,		Bacteria,		Bacteriology and antibiotic sensitivity
Demodex gatoi		Malassezia pachydermatis

Cleaning, auroscopic examination (ulcers, foreign bodies, tumours)

An initial auroscopic examination should be routine in both ears. Smali attachments, suited to the narrowness of the extemal ear canal, should be used. Sedation is sometimes necessary to examine the ear canals under optimal conditions. Auroscopic examination can reveal possible foreign bodies such as grass seeds (Hordeum spp., Avena spp.) ''^Ul3. Inflammatory changes and self-inflicted trauma should also be noted because they can alter the conformation of the ear and the cutaneous lining, making treatment difficult and perpetuating the otitis ^l0. Lichenification (Fig. 22 : 14), ulceration, oedema, dermal calcification, and sebaceous and ceruminous hyperplasia resulting from chronic inflammation must be identified. Tumours can be seen at this stage of the examination '⁴. Tumours of the extemal ear canal are uncommon in the cat⁶. Benign (e.g. papilloma, sebaceous adenoma, ceruminous gland adenoma and fibroma) and malignant tumours (e.g. sąuamous celi carcinoma, sebaceous carcinoma, ceruminous gland carcinoma, fibrosarcoma and mast celi tumour) can be seen ⁶¹⁴ (Fig. 22 : 17). Ceruminous gland tumours are the most common tumours and can completely obstruct the extemal ear canal, provoking a suppurative otitis. This is particularly common in older cats¹⁴ (Fig. 22 : 18).

22.4!

Intact:

consider myringotomy if otitis chronię

Assessment

of the tympanic membranę

Ruptured: otitis media

Look for an underlying cause