Page 291 - Small Animal Internal Medicine, 6th Edition

CHAPTER 15 Disorders of the Nasal Cavity 263

carefully into the back of the mouth around the tracheal tube and mucosa. If recurrence of fungal infection cannot be
to prevent any drug that might leak past the nasopharyngeal found and signs persist despite repeated treatments, dogs are
VetBooks.ir packing from reaching the lower airways. managed as described in the section on canine chronic/
A 10F polypropylene urinary catheter is passed into the
lymphoplasmacytic rhinitis in this chapter.
dorsal meatus of each nasal cavity to a distance approxi-
mately midway between the external naris and the medial Prognosis
canthus of the eye. The correct distance is marked on the The prognosis for dogs with nasal aspergillosis has improved
catheters with tape to prevent accidental insertion of the with debridement and repeated topical treatments. For most
catheters too far during the procedure. A 12F Foley catheter animals a fair to good prognosis is warranted. Reported
with a 5-mL balloon is passed adjacent to the polypropylene success rates were provided in the treatment section.
catheter into each nasal cavity. The cuff is inflated and pulled
snugly against the inside of the naris. A small suture is placed
across each naris lateral to the catheter to prevent balloon NASAL PARASITES
migration. A gauze sponge is placed between the endotra-
cheal tube and the incisive ducts behind the upper incisors NASAL MITES
to minimize leakage. Pneumonyssoides caninum is a small white mite approxi-
A solution of 1% clotrimazole is administered through mately 1 mm in size (see Fig. 14.13, A). Most infestations are
the polypropylene catheters. Approximately 30 mL is used clinically silent, but some dogs may have moderate to severe
for each side in a typical retriever-size dog. Each Foley cath- clinical signs.
eter is checked for filling during the initial infusion and is
then clamped when clotrimazole begins to drip from the Clinical Features and Diagnosis
catheter. The solution is viscous, but excessive pressure is not A common clinical feature of nasal mites is sneezing, which
required for infusion. Additional clotrimazole is adminis- is often violent. Head shaking, pawing at the nose, reverse
tered during the next hour at a rate that results in approxi- sneezing, chronic nasal discharge, and epistaxis can also
mately 1 drop every few seconds from each external naris. occur. These signs are similar to those caused by nasal
In dogs of the size described, a total of approximately 100 to foreign bodies. The diagnosis is made by visualizing the
120 mL will be used. mites during rhinoscopy or by retrograde nasal flushing,
After the initial 15 minutes, the head is tilted slightly to as described in Chapter 14. The mites can be easily over-
one side and then the other for 15 minutes each and then looked in the retrieved saline solution; they should be spe-
back into dorsal recumbency for 15 minutes. After this hour cifically searched for with slight magnification or by placing
of contact time, the dog is rolled into sternal recumbency dark material behind the specimen for contrast. Further,
with the head hanging over the end of the table and the nose the mites are often located in the frontal sinuses and the
pointing toward the floor. The catheters are removed from caudal nasal cavity. Flushing the nasal cavities from the nares
the external nares, and the clotrimazole and resulting mucus with an anesthetic gas in oxygen may cause the mites to
are allowed to drain. Drainage will usually subside in 10 to migrate to the caudal nasopharynx. The mites can be visual-
15 minutes. A flexible suction tip may be used to expedite ized in the nasopharynx by endoscopy during the flushing
this process. The laparotomy pads are then carefully removed procedure.
from the nasopharynx and oral cavity and are counted to
ensure that all are retrieved. The catheter in the nasopharynx Treatment
is removed. Any drug within the oral cavity is swabbed or Milbemycin oxime (0.5-1 mg/kg, orally, every 7-10 days for
suctioned. three treatments) and selemectin (6-24 mg/kg, topically over
Two potential complications of clotrimazole treatment the shoulders, every 2 weeks for three treatments) have been
are aspiration pneumonia and meningoencephalitis. Menin- used successfully for treating nasal mites. Ivermectin is also
goencephalitis is a risk when clotrimazole, polyethylene effective (0.2 mg/kg, administered subcutaneously and
glycol carrier, and/or organisms and debris from the nasal repeated in 3 weeks), but it is not safe for certain breeds. Any
cavity make contact with the brain through a compromised dogs in direct contact with the affected animal should also
cribriform plate. It is difficult to determine the integrity of be treated.
the cribriform plate before treatment without the aid of CT
or magnetic resonance imaging (MRI), although marked Prognosis
radiographic changes in the caudal nasal cavity should The prognosis for dogs with nasal mites is excellent.
increase concern. Fortunately, these complications are not
common. NASAL CAPILLARIASIS
Some dogs have a persistent nasal discharge after treat- Nasal capillariasis is caused by a nematode, Capillaria (Euco-
ment for aspergillosis. Most often the discharge indicates leus) boehmi, originally identified as a worm of the frontal
incomplete elimination of the fungal infection. However, sinuses in foxes. The adult worm is small, thin, and white
some dogs may have secondary bacterial rhinitis or sensitiv- and lives on the mucosa of the nasal cavity and frontal
ity to inhaled irritants because of the damaged nasal anatomy sinuses of dogs (see Fig. 14.13, B). The adults shed eggs that