Page 272 - Small Animal Internal Medicine, 6th Edition

244 PART II Respiratory System Disorders

interpreted in conjunction with results of nasal imaging, rhi- Frontal sinus exploration should be considered in dogs
noscopy, and nasal histology and culture. with fluid or tissue opacity in the frontal sinus in the absence
VetBooks.ir agglutination capsular antigen test (LCAT). Because organ- of a diagnosis. Aspergillosis, in particular, may be localized
The blood test of choice for cryptococcosis is the latex
within the frontal sinus and may elude diagnosis through
ism identification is usually possible in specimens from
Exploratory rhinotomy with turbinectomy is the most
infected organs, organism identification is the method of rhinoscopy.
choice for a definitive diagnosis. The LCAT is performed if aggressive diagnostic test. Surgical exploration of the nose
cryptococcosis is suspected but an extensive search for the allows direct visualization of the nasal cavity for detecting
organism has failed. The LCAT is also performed in animals the presence of foreign bodies, mass lesions, or fungal mats
with a confirmed diagnosis as a means of monitoring thera- and for obtaining biopsy and culture specimens. The poten-
peutic response (see Chapter 97). tial benefits of surgery, however, should be weighed against
Most often, computed tomography (CT) or nasal radiog- the potential complications associated with rhinotomy and
raphy, rhinoscopy, and biopsy are required to establish a turbinectomy. The Suggested Readings section offers surgical
diagnosis of intranasal disease in dogs and cats in which references.
acute viral infection is not suspected. Dental radiographs
should also be obtained if a diagnosis is not obvious from
CT or rhinoscopy, as they can be more sensitive for detecting SNEEZING
tooth root disease than CT. These diagnostic tests are per-
formed with the dog or cat under general anesthesia. CT Etiology and Diagnostic Approach
scans or nasal radiographs are obtained first, followed by oral A sneeze is an explosive release of air from the lungs through
examination and rhinoscopy, and then specimen collection. the nasal cavity and mouth. It is a protective reflex that expels
This order is recommended because results of CT or radiog- irritants from the nasal cavity. Intermittent, occasional
raphy and rhinoscopy are often useful in the selection of sneezing is considered normal. Persistent, paroxysmal sneez-
biopsy sites. In addition, hemorrhage from biopsy sites could ing should be considered abnormal. Disorders commonly
obscure or alter radiographic and rhinoscopic detail if the associated with acute-onset, persistent sneezing include
specimen were collected first. However, in dogs and cats nasal foreign body and feline upper respiratory infection.
highly suspected of having acute foreign body inhalation, The canine nasal mite, Pneumonyssoides caninum, and expo-
rhinoscopy is performed first in the hopes of identifying and sure to irritating aerosols are less common causes of sneez-
removing the foreign material. (See Chapter 14 for more ing. All nasal diseases considered as differential diagnoses
detail on nasal radiography, CT, and rhinoscopy.) for nasal discharge are also potential causes for sneezing;
The combination of radiography, rhinoscopy, and nasal however, animals with these diseases more often present
biopsy has been reported to have a diagnostic success rate of with nasal discharge as the primary complaint.
approximately 80% in dogs; however, a diagnosis of idio- The owners should be questioned carefully concerning
pathic disease was considered a diagnostic success in dogs possible recent exposure of the pet to foreign bodies (e.g.,
without progressive signs. The success rate was closer to 50% rooting in the ground, running through grassy fields) or
if the diagnosis of idiopathic disease was excluded. It is more irritants (powders and aerosols) or, in cats, exposure to respi-
difficult to evaluate the success rate for cats. High propor- ratory viruses through new cats or kittens. Sneezing is an
tions of cats with chronic nasal discharge suffer from feline acute phenomenon that often subsides with time. A foreign
chronic rhinosinusitis (idiopathic rhinitis) and are diag- body should not be excluded from the differential diagnoses
nosed only through exclusion. Dogs with persistent signs in just because sneezing subsides. In the dog a history of acute
which a diagnosis cannot be obtained after the assessment sneezing followed by the development of a nasal discharge is
described earlier require further evaluation. Cats are evalu- suggestive of a foreign body or progressive disease.
ated further only if signs suggestive of another disease are Other findings may help narrow the list of differential
found during any part of the evaluation, or if the clinical diagnoses. Dogs with foreign bodies or nasal mites may paw
signs are progressive or intolerable to the owners. at their nose. Foreign bodies are typically associated with
Nasal CT is considered if not performed previously and unilateral, mucopurulent nasal discharge, although serous or
if a diagnosis has not been made. CT provides excellent serosanguineous discharge may be present initially. Foreign
visualization of all of the nasal sinuses and may allow iden- bodies in the caudal nasopharynx may cause gagging, retch-
tification of small masses that are not visible on nasal radi- ing, or reverse sneezing. The nasal discharge associated with
ography or rhinoscopy. CT is also more accurate than nasal reactions to aerosols, powders, or other inhaled irritants is
radiography in determining the extent of nasal tumors. Mag- usually bilateral and serous in nature. In cats other clinical
netic resonance imaging (MRI) may be more accurate than signs supportive of a diagnosis of upper respiratory infec-
CT in the assessment of soft tissues, such as nasal neoplasia. tion, such as conjunctivitis and fever, may be present as well
Dental radiographs should also be obtained if not previously as a history of exposure to other cats or kittens.
performed. In the absence of a diagnosis, nasal imaging Dogs in which acute, paroxysmal sneezing develops should
(preferably CT or MRI), dental radiographs, rhinoscopy, and undergo prompt rhinoscopic examination (see Chapter 14).
biopsy can be repeated after a 1- to 2-month period. With time, foreign material may become covered with mucus