Padraic Dixon, Eric Parente, Tim Barnett, et al.
Background
Equine sinonasal disease is often chronic, difficult to diagnose, and frequently accompanied by concurrent nasal pathology. Previous studies have been limited in size, leaving uncertainty regarding common clinical presentations, pre-referral management, and factors influencing treatment success. This multicenter study aimed to characterize historical, clinical, and nasal endoscopic findings in CT-confirmed equine sinonasal disease and identify variables associated with complete cure after referral.
Methods
This retrospective multicenter case series collected standardized clinical data from 19 equine referral hospitals between 2010 and 2024. A total of 1,600 horses with CT-confirmed sinonasal disease were included, comprising 1,457 unilateral and 143 bilateral cases. Data included signalment, disease duration, pre-referral medical and surgical treatments, clinical signs, nasal endoscopic findings, and treatment outcomes. Multivariable logistic regression was performed on 650 cases with complete datasets to identify factors associated with complete cure.
Results
The median age of affected horses was 12 years, and disease duration before referral was 8 weeks, although some horses had clinical signs for several years. Before referral, 61.2% received antimicrobials, most commonly potentiated sulphonamides, doxycycline, and procaine penicillin, while 32.3% received NSAIDs. Previous surgical interventions included sinoscopy in 11.8%, nasofrontal sinusotomy in 5.2%, maxillary sinusotomy in 3.6%, and maxillary cheek tooth extraction in 12.6% of horses.
At referral, 85.4% had nasal discharge, 41.1% had malodorous discharge, 26.9% exhibited facial swelling, and 14.9% had nasal airflow obstruction. Nasal endoscopy identified exudate draining from the sinonasal ostium in 65.8% of examined horses and middle meatus abnormalities—including inspissated exudate, sequestra, sinonasal fistulae, and conchal abnormalities—in 44.6%.
Among the 926 horses with outcome data, 69.7% achieved complete cure, 16.8% were partially cured, and 13.5% were not cured. Multivariable analysis demonstrated that horses older than 12 years, disease lasting more than 8 weeks, previous nasofrontal sinusotomy, facial swelling, nasal airflow obstruction, and bilateral nasal discharge were all independently associated with lower odds of complete cure.
Limitations
The retrospective design resulted in incomplete clinical records for some variables, and not every horse underwent identical diagnostic procedures. Outcome analysis included only a subset of cases with complete datasets, and differences in referral practices between participating hospitals may have influenced case selection and management.
Conclusions
This largest reported series of equine sinonasal disease demonstrates that these disorders are frequently chronic before referral and commonly receive prolonged antimicrobial treatment despite limited effectiveness in many cases. Older horses, longer disease duration, previous nasofrontal sinusotomy, facial swelling, nasal airflow obstruction, and bilateral nasal discharge were associated with reduced likelihood of complete cure. The findings support earlier referral, greater use of advanced imaging, and improved evidence-based management guidelines for equine sinonasal disease.
Key Takeaways
1,600 horses from 19 referral hospitals make this the largest equine sinonasal disease study to date.
61.2% received antimicrobials before referral, despite many cases representing conditions unlikely to resolve with antibiotics alone.
65.8% showed exudate at the sinonasal ostium during nasal endoscopy.
44.6% had middle meatus abnormalities, highlighting the diagnostic value of careful endoscopic examination.
69.7% achieved complete cure after referral treatment.
Age over 12 years, disease lasting more than 8 weeks, facial swelling, nasal airflow obstruction, bilateral nasal discharge, and prior nasofrontal sinusotomy all reduced the likelihood of complete cure.
Clinical Pearl
One of the study's strongest practical messages is that prolonged antimicrobial therapy should not delay definitive diagnosis. The authors emphasize that chronic dental sinusitis, sinus cysts, progressive ethmoid hematomas, neoplasia, and many other sinonasal disorders are unlikely to resolve with antibiotics alone, making early CT imaging and targeted treatment more likely to improve outcomes before chronic anatomical changes develop.
Transverse computed tomographic (CT) images (bone window) of two cases of sinusitis. (A) This case of bilateral dental sinusitis has
bilateral rostral maxillary sinus (RMS) involvement, with some mucosal thickening but minimal exudation in the right RMS (left side of image). Bilateral
apical infections with gas attenuation within pulp horns and abnormal, widened periapical spaces (white arrows) are present, along with a buccal (first and
second pulp horn; ‘slab’) fracture on the right infected tooth (yellow arrow). Bilateral destructive-type changes are present in both ventral nasal conchal
bullae (stars). (B) This case of unilateral right-sided sinusitis has heterogeneous, soft-tissue attenuation of the right dorsal conchal sinus (yellow star), and
of the distended rostral maxillary and ventral conchal sinuses (white stars) that also have foci of gas attenuation (indicative of inspissated exudate)
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