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Key takeaways

Ethmoid hematomas in horses are noncancerous masses that develop on the ethmoids, a highly vascularized area of the nasal cavity

  • These masses are very fragile and prone to bleeding, resulting in bloody nasal discharge
  • Some masses may obstruct airflow through the nasal cavity, causing difficulty breathing
  • Ethmoid hematomas are diagnosed through a physical examination, endoscopy of the nasal cavity, and diagnostic imaging
  • Treatment involves surgical removal, laser therapy, cryotherapy or injection of formalin into the mass
  • Symptoms often resolve with treatment, however the masses frequently recur
  • Ongoing monitoring of horses diagnosed with ethmoid hematomas is recommended to identify recurrence early
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A closer look: Ethmoid Hematomas in Horses

Ethmoid hematomas are noncancerous masses within the nasal cavity of horses. They are uncommon in horses, and are not usually life-threatening.

Prompt veterinary intervention is recommended for horses showing symptoms of ethmoid hematomas, in order to prevent recurring nosebleeds or difficulty breathing. Horses with large amounts of bloody discharge require immediate veterinary attention, as this may be a sign of more serious conditions such as guttural pouch disease.

Risk factors

In some cases, there may be no symptoms of ethmoid hematomas, particularly if the masses are small. Large masses may be visible within the nostril if they extend down the nasal cavity, and in some cases the size of the mass results in obvious facial deformity.

Possible causes

There are no known underlying causes or risk factors for these masses, and they can affect horses of any age, breed, or gender.

Main symptoms

The symptoms of ethmoid hematomas are primarily associated with bleeding from the mass.

Testing and diagnosis

Most horses with ethmoid hematomas are identified due to initial bloody nasal discharge, so diagnosis primarily focuses on identifying the source of bleeding. Diagnostics may include:

  • Physical examination
  • Endoscopy of the nasal cavities
  • Diagnostic imaging, such as X-rays or ultrasound
  • Biopsy of the mass

Steps to Recovery

Treatment of ethmoid hematomas can be difficult due to the location of the mass within the head, preventing easy access. Treatment options may include:

  • Surgical removal through a flap created in the skull
  • Laser treatment
  • Cryotherapy
  • Injection of formalin into the mass

Horses often require multiple treatments to fully remove the mass, and masses frequently reappear even after successful treatment. Regular examination of the nasal cavity is recommended to identify recurrence early. Most cases of ethmoid hematomas can be managed with ongoing monitoring and treatment as needed.


There are no known preventatives for ethmoid hematomas. Ethmoid hematomas are not contagious.

Is Ethmoid Hematomas in Horses common?

Ethmoid hematomas are uncommon in horses.

Typical Treatment

  • Surgical removal
  • Formalin injection
  • Cryotherapy
  • Laser treatment


Jean-Pierre Lavoie DVM, DACVIM - Writing for Blackwell's Five-Minute Veterinary Consult: Equine, 3rd Edition
Lindsey Boone, DVM, PhD, DACVS-LA - Writing for Merck Veterinary Manual
No Author - Writing for Fox Valley Equine Practice

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