Diagnosed causes of sinonasal disease in 1600 horses and associations with clinical signs, computed tomographic findings and case outcome.

BACKGROUND: The diagnosis of equine sinonasal disorders has been greatly enhanced by using computed tomographic (CT) imaging. OBJECTIVES: To explore associations between specific diagnoses and clinical and CT findings and between specific diagnoses and case outcome in equine sinonasal disease. STUDY DESIGN: Retrospective case series. METHODS: Data were collected from medical records from 19 equine hospitals on cases of sinonasal disease, all of which underwent CT imaging. Case outcome was obtained from clinical records, and/or by contacting clients and referring veterinarians. Logistic regression analysis was used to examine associations between specific diagnoses and clinical and CT variables and examine associations between specific diagnoses and case outcome. RESULTS: Dental sinusitis due to apical infection was the most common cause of sinusitis (n = 693; 43.3% of cases). Other causes were primary sinusitis (n = 329; 20.6%), sinus cyst (n = 178; 11.1%), progressive ethmoid haematoma (PEH) (n = 100; 6.3%), traumatic sinonasal disease (n = 90; 5.6%), sinonasal neoplasia or suspect neoplasia (n = 86; 5.4%), other non-neoplastic sinonasal growths (n = 11; 0.6%), mycotic infection (n = 65; 4.1%), sinus pneumocele (n = 5; 0.3%), oro-nasal fistulae-related sinusitis (n = 4; 0.25%), sinus mucocele (n = 2; 0.13%) and facial suture infection (n = 1; 0.06%) cases. Facial swelling was more common with sinonasal cysts, tumours, trauma and mycosis than other diagnoses. Nasal malodour was most common with dental sinusitis. Nasal airflow obstruction was most common with sinonasal cysts, PEH and tumours. Empyema of the nasal conchal bullae was least common with sinus cysts, PEH, trauma and tumours (less purulent types of sinusitis). More severe grades of hyperostosis were associated with sinus cysts and tumours. Sinonasal tumours (odds ratio [OR] 0.03, 95% confidence interval [CI] 0.01-0.07) and PEH (OR 0.23, 95% CI 0.12-0.43) had a significantly lower likelihood of cure than primary sinusitis. MAIN LIMITATIONS: This was a retrospective study, and histology was not performed in some cases. CONCLUSIONS: Equine sinonasal disease has a range of underlying causes which impacts the clinical presentation and outcome.