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Archive Case #66: Equine Sinusitis

Horse veterinary case - Medium - May 8, 2026

Clinical Clues

  1. A horse is examined for persistent unilateral nasal discharge that has become foul smelling.
  2. The discharge is worse when the head is lowered during eating.
  3. There is mild facial sensitivity over one sinus region.
  4. Airflow from both nostrils is still present, but only one side is affected by discharge.
  5. Endoscopy and imaging support fluid accumulation within the paranasal sinus system.
  6. Inflammation or infection within the equine sinuses commonly causes unilateral purulent nasal discharge.

Diagnosis

Equine Sinusitis

This case is most consistent with Equine Sinusitis because the horse has unilateral malodorous nasal discharge localised to the sinus region. The most important clues are the one-sided discharge and sinus fluid accumulation, which make a lower respiratory problem much less likely.

Learning review

Review the case evidence

Use the paired clues to explain how the evidence in this horse case supports the provided diagnosis, Equine Sinusitis, then compare your reasoning with the case explanation.

Evidence checkpoints

Clues 1-2

  1. Clue 1: A horse is examined for persistent unilateral nasal discharge that has become foul smelling.
  2. Clue 2: The discharge is worse when the head is lowered during eating.

Clues 3-4

  1. Clue 3: There is mild facial sensitivity over one sinus region.
  2. Clue 4: Airflow from both nostrils is still present, but only one side is affected by discharge.

Clues 5-6

  1. Clue 5: Endoscopy and imaging support fluid accumulation within the paranasal sinus system.
  2. Clue 6: Inflammation or infection within the equine sinuses commonly causes unilateral purulent nasal discharge.

Self-review prompts

  1. After clues 1-2, what evidence from this horse case shaped your initial interpretation?
  2. When you compare clues 3-4 with clues 1-2, what changed in your reasoning about Equine Sinusitis?
  3. How do clues 5-6 align with the case explanation for Equine Sinusitis?

Educational Use

Vetdle archive cases are educational veterinary games for diagnostic reasoning practice. They do not provide veterinary advice, diagnosis, treatment, or professional medical guidance.