Cytological Examination of Secretions From the Paranasal Sinuses in Horses.
Authors: Gergeleit Hauke, Bienert-Zeit Astrid, Seemann-Jensen Anja, Delarocque Julien, Ohnesorge Bernhard
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Cytological Examination of Equine Paranasal Sinus Secretions Distinguishing between primary sinusitis, dental disease, cysts, and other sinus pathologies in horses remains clinically challenging, prompting investigation into whether cytological analysis of sinus secretions could help differentiate aetiologies. Researchers collected samples from 50 horses with sinusitis and 10 healthy controls via transendoscopic catheterisation of the nasomaxillary aperture (with direct sampling via osteotomy in 19 diseased cases), then stained samples using Pappenheim stain for microscopic evaluation. Healthy sinuses contained almost exclusively epithelial cells, whilst diseased sinuses showed moderate-to-high neutrophil populations; dental-related sinusitis notably displayed increased cellular debris and substantially higher intracellular and extracellular bacterial loads compared to other aetiologies. Whilst cytological examination can support clinical suspicion—particularly for bacterial dental-related disease—the findings underscore that this technique provides only ancillary diagnostic value and cannot reliably exclude infection when bacteria are absent on light microscopy, making it essential to combine cytology with bacterial culture, imaging, and endoscopic findings rather than relying on cytology alone. For practitioners, this reinforces that whilst sinus cytology offers a non-invasive sampling method that may strengthen diagnostic confidence in suspected dental sinusitis, negative microscopic findings should not delay further investigation.
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Practical Takeaways
- •Cytological examination of sinus secretions can support but should not replace other diagnostic methods (endoscopy, imaging, bacterial culture) when evaluating equine sinusitis
- •Higher bacterial load on cytology may suggest dental-related sinusitis, potentially directing further investigation toward dental examination and treatment
- •Negative bacterial findings on microscopy do not rule out bacterial infection; bacterial culture remains necessary for definitive diagnosis and antimicrobial selection
Key Findings
- •Sinusitis smears showed moderate to high neutrophilic granulocytes and moderate epithelial cells, whereas healthy sinuses contained almost exclusively epithelial cells
- •Dental-related sinusitis (n=28) contained more lytic cellular material and higher intracellular/extracellular bacterial burden compared to other etiologies
- •Absence of bacteria on light microscopy did not exclude pathogenic bacteria identified by bacterial culture
- •Cytological examination provides limited ancillary diagnostic value in equine sinusitis due to small case numbers for neoplasia and progressive ethmoidal hematoma evaluation