Page 280 - Small Animal Internal Medicine, 6th Edition

252 PART II Respiratory System Disorders

Alternatively, the caudal nasopharynx can be evaluated with
the aid of a dental mirror, penlight, and spay hook, which is
VetBooks.ir attached to the caudal edge of the soft palate and pulled
forward to improve visualization of the area. It may be pos-
sible to visualize nasal mites of infected dogs by observing
the caudal nasopharynx while flushing anesthetic gases (e.g.,
isoflurane and oxygen) through the nares.
Rhinoscopy must be performed patiently, gently, and
thoroughly to maximize the likelihood of identifying gross
abnormalities and to minimize the risk of hemorrhage. The
more normal side of the nasal cavity is examined first. The
tip of the scope is passed through the naris with the tip
pointed medially. Each nasal meatus is evaluated, beginning
ventrally and working dorsally. Each nasal meatus should be
examined as far caudally as the scope can be passed without A
trauma.
Although the rhinoscope can be used to evaluate the large
chambers of the nose, many of the small recesses cannot be
examined, even with the smallest endoscopes. Thus disease
or a foreign body may be missed if only these small recesses
are involved. Swollen and inflamed nasal mucosa, hemor-
rhage caused by the procedure, and the accumulation of
exudate and mucus can also interfere with visualization of
the nasal cavity. Foreign bodies and masses are frequently
coated and effectively hidden by seemingly insignificant
amounts of mucus, exudate, or blood. The tenacious material
must be removed using a rubber catheter with the tip cut off
attached to a suction unit. No catheter should ever be passed
blindly into the nasal cavity beyond the level of the medial
canthus of the eye to avoid entering the cranial vault through
the cribriform plate. B
If necessary, saline flushes can also be used, although
resulting fluid bubbles may further interfere with visualiza- FIG 14.12
(A) Rhinoscopic view through the external naris of a dog
tion. Some clinicians prefer to maintain continuous saline with aspergillosis showing erosion of turbinates and a
infusion of the nasal cavity using a standard intravenous green-brown granulomatous mass. (B) A closer view of the
administration set attached to a catheter or, if available, the fungal mat shows white, filamentous structures (hyphae).
biopsy channel of the rhinoscope. The entire examination is
done “underwater.”
Particular care must be exercised to avoid aspiration
of blood or saline into the lungs, particularly if saline is dorsal), the medial-to-lateral orientation within the meatus,
infused. The clinician must be sure the endotracheal tube and the distance caudal from the naris. Exact localiza-
cuff is fully inflated and the back of the pharynx is packed tion is critical for directing instruments for the retrieval
with gauze. The gauze should be checked frequently and of foreign bodies or nasal biopsy specimens should visual
replaced if saturated. The clinician must be careful not to guidance become impeded by hemorrhage or size of
overinflate the endotracheal tube cuff, which could result in a the cavity.
tracheal tear.
The nasal mucosa is normally smooth and pink, with a
small amount of serous to mucoid fluid present along the FRONTAL SINUS EXPLORATION
mucosal surface. Potential abnormalities visualized with the
rhinoscope include inflammation of the nasal mucosa; mass Occasionally the primary site of disease is the frontal sinuses,
lesions; erosion of the turbinates (Fig. 14.12, A); mats of most often in dogs with aspergillosis. Boney destruction
fungal hyphae (see Fig. 14.12, B); foreign bodies; and, rarely, may be sufficient to allow visualization and sampling by
nasal mites or Capillaria worms (Fig. 14.13). Differential rhinoscopy through the external naris. However, in cases
diagnoses for gross rhinoscopic abnormalities are provided with evidence of frontal sinus involvement on imaging
in Box 14.2. studies and the absence of a diagnosis through rhinoscopy
The location of any abnormality should be noted, and biopsy, surgical exploration of the frontal sinus may
including the meatus involved (common, ventral, middle, be necessary.