Page 1540 - Clinical Small Animal Internal Medicine

1478 Section 12 Skin and Ear Diseases

onto the swab or suctioned up the catheter to sample
VetBooks.ir the middle ear.
If the tympanic membrane is intact but appears
abnormal, it is possible a previous defect in the tympa-
num has healed in the presence of ongoing otitis media.
In these cases, myringotomy should be performed to
take samples from the middle ear. Direct visual obser-
vation (ideally with a video otoscope) in a carefully
cleaned ear canal is important to avoid damage to sen-
sitive structures. The myringotomy should be per-
formed by an experienced clinician using a diode or
carbon dioxide (CO 2 ) laser or manually using a sterile
rigid polypropylene catheter cut to an angle of 60°. A
small hole made in the pars tensa in the caudoventral
Figure 167.8 A swab being passed through a sterile otoscope quadrant to avoid the pars flaccida and the manubrium
cone, which guards the swab from discharge and contaminants of the malleus (Figure 167.9) allows for collection of
present in the vertical ear canal during cytologic sampling.
material from the middle ear, which can be examined
cytologically and submitted for culture and sensitivity.
Cytology in otitis externa is useful but in otitis media,
the presence of mucus from the middle ear can make
identification of bacteria difficult. Where cytology
reveals signs of an inflammatory infiltrate and infec-
tious organisms, a definitive diagnosis of otitis media
can be made. Where cytology is unremarkable, cul-
tures are necessary and are probably best undertaken
in all cases.
Advanced imaging is useful in otitis media. Radiography
is only diagnostic in chronic disease. The open‐mouthed
view, which allows for comparison of both sides, and the
lateral oblique view provide the most information.
Changes on radiography that are consistent with otitis
media are increased density of the air‐filled bulla, thick-
ening, lysis or irregularity of the tympanic bulla wall, or
formation of new bone. Computed tomography (CT) and
magnetic resonance imaging (MRI) are more sensitive
modalities, picking up subtle changes such as granulation
tissue or fluid or mucus within the middle ear.

Figure 167.9 Videootoscopic image of a normal tympanic
membrane in a dog. Black arrow indicates the recommended site Therapy
of myringotomy in the caudoventral quadrant of the pars tensa.
Therapy of otitis media may be divided into several
stages:
tympanic membrane can be visualized and can be seen
to be ruptured or intact but abnormal, suggesting pre- ● flushing the bulla
vious damage, then a diagnosis of otitis media is possi- ● infusion of topical medication(s) into the bulla
ble. If the tympanic membrane is ruptured, samples ● reduction of inflammation with glucocorticoids
may be taken from the middle ear. A clean otoscope ( topical or systemic)
cone or videootoscope head should be inserted as far ● administration of systemic antibiotics
into the horizontal canal as possible and a fine catheter ● reassessment every 7–10 days
or microswab may be inserted through the tube or Continue therapy until negative cytology and cultures
working channel to “guard” it from discharge in the have been achieved and the ear appears clinically
external canal (Figure 167.8). Material can be gathered normal.