[Nasal discharge in dogs - are microbiological and histopathological examinations clinically useful?]

Retrospective evaluation of the diagnostic value of bacterial culture of nasal mucosal swabs and histopathologic assessment of nasal mucosal biopsies in dogs with nasal discharge.

Medical records of dogs with the predominant clinical sign of nasal discharge that were referred to the ENT Unit of the Small Animal Department between January 2015 and December 2016 were reviewed.

Data of 85 dogs were evaluated. On the basis of the results of computed tomography (CT), rhinoscopy, bacterial culture of a nasal mucosal swab and histopathologic examination of nasal mucosal biopsies, dogs were assigned to one of six groups of primary nasal diseases: nasal neoplasia (24/85, 28 %), oronasal defect (22/85, 26 %), idiopathic chronic rhinitis (17/85, 20 %), foreign body (8/85, 10 %), sinonasal aspergillosis (7/85, 8 %) and diseases of the planum nasale (7/85, 8 %). In brachycephalic dogs (14/85, 17 %), oronasal defects (8/14, 57 %) were the most frequent cause of nasal discharge. No cases of a primary bacterial infection of the nasal cavity were observed and, therefore, antibiotic treatment had not been successful. Nevertheless, 72 % of the dogs in this study had received prior antibiotic treatment. Secondary bacterial infec tions diagnosed via nasal mucosal swabs were not diagnostic for the underlying primary nasal diseases. Targeted biopsies of tumors obtained under endoscopic visualization may lead to a definitive diagnosis, whereas biopsies of the nasal mucosa and the type of the inflammatory infiltrate were not diagnostic.

Nasal discharge in dogs is frequently an indicator of an underlying severe primary nasal disease possibly leading to mortality of the affected dogs. Further diagnostics under anesthesia should be performed early in the diagnostic evaluation. Rhinoscopy as the central diagnostic is supported by CT and biopsy. Bacterial culture of the nasal discharge does not provide a diagnosis for the primary nasal disease process.

Without further diagnostics, antibiotic treatment of dogs presenting with nasal discharge is considered as not appropriate and can be harmful in dogs with nasal tumors or sinonasal aspergillosis. When an intranasal malignant neoplasia is suspected, endoscopic-guided biopsies of the nasal mass should be obtained, because blind nasal biopsies are associated with a high rate of false-negative results.