TEST YOUR DIAGNOSTIC SKILL

A 14-year-old, 513-kg quarter horse gelding was presented to the Color ado State University Veterinary Teaching Hospital. The horse had a two -month history of a unilateral left nasal discharge. Initially, the ex udate began as an intermittent serous discharge and gradually became p urulent with episodes of mild epistaxis. At this time, several courses of trimethoprim-sulfa antibiotic therapy were administered; there was minimal response. The horse slowly became exercise intolerant. Three weeks before presentation, a mass was noticed protruding from the left nasal cavity into the left nostril. The mass continued to enlarge. At presentation, the horse was alert with a normal body temperature and pulse rate. There was an increase in respiratory rate and minimal move ment of air through the left nostril. The mass was protruding external ly from the left nasal cavity, and a malodorous purulent discharge was present. Endoscopy was attempted, but because of the size of the mass , the endoscope could not be advanced. Survey radiographs and a positi ve-contrast sinogram were performed to facilitate a diagnosis.