Nasal Abscess and Associated Oronasal Fistula in a Mare

A 20-year-old Warmblood broodmare was presented to the primary veterinarian for bilateral nasal discharge, which had been treated with sulfamethoxazole without complete resolution. The mare was referred to Cornell’s Equine Hospital after she began dropping feed without losing weight. Oral exam, radiography, computed tomography (CT) of the head, and upper airway endoscopy were performed, revealing a left sided nasal abscess filled with feed material due to an associated oronasal fistula between the left maxillary premolars (207 and 209) with reactive bone extending past 210. The abscess was debrided, and drainage was established via a transnasal standing approach under endoscopic guidance, with conservative management of the affected teeth. Repeated follow-up evaluations included upper respiratory endoscopic and oral endoscopic exams to monitor abscess resolution and to evaluate the compromised periodontal attachment of the affected teeth. This case highlights 1) the importance of advanced imaging in cases of equine nasal and sinus disease and 2) the success of conservative dental management when faced with a case of severe periodontitis with subsequent oronasal fistulation.