Oronasal fistula is an acquired communication lined by the epithelium between the oral and nasal cavities. The most common cause of an oronasal fistula in dogs is advanced periodontal disease, when thin bone between the root of the maxillary teeth and nose is destroyed by the chronic inflammation. In cats, an oronasal fistula from periodontitis is less common due to a different anatomy.
Oronasal fistula can also be a sequel of trauma (e.g., bite wounds, blunt head trauma, gunshot wounds, electrical burns, foreign body penetration and pressure necrosis, chronic malocclusion), tumors, radiation therapy of the upper jaw and nose (radiation necrosis), dental disease and dehiscence after surgical treatment of the congenital or aquired palatal defects or complicated tooth extractions. Infections (fungal, bacterial) may also result in subacute, invasive inflammatory processes with extensive tissue necrosis and oronasal fistulation.
Animals with an oronasal fistula will usually have nasal discharge (on the side of the fistula), which is usually serous, but may also be bloody or mucopurulent (resemble pus). Sneezing, pawing at the nose and bad breath are also common. If the defect is large, water and food may appear on the nostrils during drinking or eating.
Oronasal fistula is best diagnosed by detailed oral and dental examination. During periodontal probing, the periodontal probe will »sink« into the nose, causing bleeding from the ipsilateral nostril. This clinical finding should be supported by dental radiographs and in cases of more extensive oronasal fistulation by computed tomography (CT).
Rhinoscopy (examination of the nose with the endoscope), biopsy and/or tissue sampling for culture and sensitivity should be performed as clinically indicated.
Oronasal fistula requires surgical repair. The first surgery brings the best chances for success. Therefore all necessary diagnostic procedures should be performed to accurately plan the surgical repair before it is attempted.
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