Use of computer-assisted tomography for diagnosis and standing surgical reduction of progressive ethmoidal hematoma in a mare.

Progressive ethmoidal hematoma (PEH) is a rare, nonneoplastic mass occurring in the sinonasal passages of horses. An 11-year-old, pregnant Thoroughbred mare was presented with a history of intermittent nasal discharge and stertorous respiration. On examination, radiography revealed increased opacity in the sinus and nasal cavities and endoscopy identified a mass emerging from the left ethmoidal turbinate. Computed tomography (CT) showed the range and origin of the mass, indicative of PEH. A standing frontonasal flap was made under sedation, following temporary tracheostomy to secure the airway. The mass was exposed via a frontonasal bone flap and was removed after double ligations. The histopathologic examination confirmed that the mass was PEH. The mare showed no postoperative complications and subsequently gave birth. Key clinical message: This case report describes the diagnostic process, using radiography, endoscopy, and CT, and details the surgical reduction and outcome of PEH in a mare. It highlights the value of CT in localizing and measuring PEH, facilitating surgical planning.