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Nasal examination and aspergillosis (Proceedings)

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Aug 01, 2009

Nasal problems are a frequent reason for seeking veterinary care. Sneezing that produces a nasal discharge or frank hemorrhage must be evaluated to identify the underlying cause. A variety of historical factors such as age of the dog, vaccination status, the breed and the environment will influence the likelihood of certain diseases. A mucopurulent nasal discharge in a young, sick dog with a questionable vaccination history requires exclusion of distemper. In sporting dogs with an acute onset of violent sneezing, nasal foreign bodies especially grass awns must be considered. Nasal fungal infections with Aspergillus sp. occur most commonly in dolichocephalic dogs that are under 5 years of age while nasal tumors are more common in older dogs but can occur in dogs as young as 18 months of age. Seasonal episodes of nasal discharge suggest an allergic component. Most nasal conditions do not produce lethargy or fever except for infectious diseases like distemper and some cases of aspergillosis.

Dogs with acute hemorrhagic discharge must be evaluated for bleeding disorders especially platelet abnormalities. Hypertension has also been associated with nosebleeds. While bleeding occurs in aspergillosis and nasal tumors, there is usually a long history of mucopurulent nasal discharge. Unilateral discharges can occur with foreign bodies, tumors and aspergillosis initially but aspergillosis and tumors often progress to bilateral discharges when there is destruction of the nasal septum. Tooth root abscesses of the upper 4th premolar tooth that drain into the nasal passages may also produce unilateral nasal discharges. Nasal discharges may improve with antibiotic treatment but most nasal diseases have secondary bacterial involvement that will temporarily respond. Primary bacterial infection of the nose of the dog is not a common condition.

A thorough physical examination to identify more generalized conditions may reveal the generalized lymphadenopathy associated with lymphoma of the nasal passages, dental disease with root abscesses, cleft palate with food entry into the nose, metastatic nasal tumors, chorioretinitis associated with distemper or cryptococcosis, pharyngeal masses, ulcerative depigmented lesions of the nares characteristic of aspergillosis and other abnormalities that would limit anesthesia for imaging and rhinoscopy. Neurologic abnormalities may be seen in invasion of the brain by aspergillosis or tumors. It is very helpful to obstruct one nostril and listen to the airflow through the other nostril. Complete obstruction of airflow is usually associated with nasal tumors though some conditions such as aspergillosis have large amounts of discharge that can obstruct the nostril.

A complete blood count, chemistry panel and urinalysis is a good basic data base in dogs with persistent nasal problems. While the changes are not usually diagnostic certain conditions such as hypergammaglobulinemia and thrombocytopenia may be noted with ehrlichiosis. Aspergillosis and sinusitis may have a leukocytosis. Imaging is very helpful in identifying the etiology of nasal problems. Lateral and open mouth VD views of the nasal passages are helpful but CT or MR scans of the head are more likely to characterize and localize the disease process. A sky line view of the frontal sinuses also identifies sinus involvement. Imaging defines the best area to search for a diagnosis. Aspergillosis produces destruction of the turbinates resulting in cavernous areas in the nose. Nasal tumors also destroy the turbinates and nasal bones but the area becomes filled with tumor. Under anesthesia, examine the hard palate for soft spots suggestive of boney destruction and explored the area under the soft palate with a finger to identify polyps and tumors in the area. The area can be visualized and biopsied with a flexible scope. The nasal passages can be examined with a rigid or flexible scope but a lot of information can be obtained by examining the nose with an otoscope speculum. Use the largest speculum that you can pass through the nares. Tumors lack the smooth, glistening appearance of normal turbinates. Whitish-grey plaques can be seen on inflamed mucosa in some aspergillosis cases. In aspergillosis, the destruction of the turbinates can be appreciated by noting the openness of the nasal passages. Abnormal areas that are visualized can be biopsied for culture and histopathology. The biopsied tissue should be cultured not the exudate. With luck, nasal foreign bodies can be identified and removed. When there are excessive discharges or hemorrhage blind biopsies of "areas of interest" noted on imaging can be done. Aggressive sampling will identify an etiology in many cases. Care must be taken in the biopsy procedure because many dogs have erosion of the cribriform plate. To avoid the area of the cribriform plate, biopsies must not be taken caudally to a vertical plane in the area of the medial canthus of the eyes.