Ethmoid Haematomas

When a horse presents with persistent or intermittent haemorrhagic nasal discharge (bleeding from the nostrils) your vet may investigate for an uncommon but problematic ethmoid haematoma. So what is it? what causes it? and how can it be treated? Veterinarian, Sarah Van Dyk explains…


A part of the horse’s anatomy that most horse owners may be less familiar with are the ethmoid turbinates.
The ethmoid turbinates are a collection of thin scroll shaped bones covered in respiratory epithelium located at the back of the horse’s nasal passage (see anatomy image on right).

It is responsible for cleaning, warming and humidifying air that is breathed in. There are a lot of blood vessels concentrated within the tissue covering the ethmoid turbinates and this is often the origin of bleeding after nasogastric tubing or head trauma.

The ethmoid turbinates and nasal passage of the horse communicates with air filled cavities within the horse’s skull called the paranasal sinuses.

The paranasal sinuses are located at the front of the skull extending from between the horse’s eyes to approximately two thirds down the horse’s face.

The problem

An ethmoid haematoma is a benign encapsulated mass that forms within the ethmoid turbinates or paranasal sinus.

Although technically benign, ethmoid haematomas tend to continue to grow, leading to localised obstruction of the airways, possible destruction of the nasal turbinates and chronic haemorrhagic nasal discharge. A haematoma by definition is an abnormal localised collection of blood outside the blood vessels.

The exact cause of ethmoid haematomas is unknown however they are thought to develop from a small bleed within the submucosa of the respiratory epithelium which causes the tissue to stretch, thicken and form a capsule. This continues, leading to a slowly expanding mass.

Signs to look for

Horses that develop this condition are generally middle aged and older and there appears to be a predilection for Arabian and Thoroughbred horses although this may be a population based statistic. There doesn’t appear to be a definitive predilection relating to gender.

The most common clinical sign of an ethmoid haematoma is intermittent serosanguinous or haemorrhagic discharge usually from one nostril. This may start as occasional drops of blood or a small trickle every so often and progress over several months to more pronounced epistaxis.

Other signs are less common but may include upper respiratory noise, chronic purulent nasal discharge, malodorous breath, facial swelling, head shaking, exercise intolerance and a visible mass in the nostril.

Unilateral epistaxis (bleeding from one nostril only) is the most common clinical sign of an ethmoid haematoma.


If you suspect your horse may be suffering from this condition, it is best to consult your veterinarian straight away.

A diagnosis can be made based on history, clinical signs, radiographs and endoscopy.

Radiographing the horse’s head enables the veterinarian to visualise the size and location of the mass within the skull. This becomes important when making decisions on treatment options and prognosis.

The lateral (side) view of the skull is most diagnostic and a characteristic smooth, discrete, rounded density can usually be seen within the sinuses.

Endoscopy involves passing an endoscope, which is essentially a long tube with a camera on the end, up the nose and into the nasal passage.

In some cases, it is difficult to ascertain the size or even the presence of a mass with just endoscopy as the ethmoid haematoma may be located partially or completely within the paranasal sinus which is impossible to visualise with endoscopy through the nasal passage. For this reason, radiographs and endoscopy are best performed together for diagnosis.

Ethmoid haematomas have a very characteristic appearance on endoscopy, therefore endoscopic guided biopsy of the mass is generally not necessary to make a diagnosis and the risks of bleeding and not getting a representative sample outweigh the benefits of a biopsy.

An ethmoid haematoma generally appears as a red or yellow to green tinged mass visible with endoscopy.


There are two main treatment options for this condition, both of which involve a certain amount of risk.
Surgical treatment is the most common. Surgery can be done under a general anaesthetic or standing under heavy sedation.

It involves creating a bone flap through into the frontal sinus to access the ethmoid haematoma directly. The haematoma is removed through the flap using curettage and gentle surgical manipulation. Laser ablation and cryogenic ablation through the sinus flap are other techniques that can be used. There is a risk of excessive bleeding during surgery however generally this is able to be managed sufficiently. Surgery gives the surgeon the advantage of visualisation of the sinus to increase the chances of complete removal.

The least invasive option is chemical ablation. The procedure is performed standing under sedation through the nostrils. Formalin is injected into the mass through a catheter passed into the endoscope. The tissue dies and sloughs away 5-10 days post injection and the procedure is repeated at regular intervals until there is no evidence of the haematoma remaining. This option doesn’t account for large lesions that may be mostly hidden from view from the endoscope or lesions that are not accessible through the nostrils via endoscopy.

In some cases, treatment may include a combination of these techniques.

An ethmoid haematoma after surgical removal, note the greenish tinged capsule.

It hasn’t been definitively proven which treatment is better; however it is essential to remove the encapsulated mass in its entirety to have the best chance of avoiding recurrence. The access to the mass which surgery provides seems to make this option more favourable.

To conclude

Prognosis for a horse with an ethmoid haematoma left untreated is poor as the mass is progressive and eventually causes obstruction and destruction of the nasal passage.

Prognosis with treatment is good, however recurrence rates of 20%-50% have been reported depending on method of treatment. Recurrence can occur months and even years after initial treatment therefore regular rechecks are recommended so prompt follow up treatment can be instituted.

Although it can be an ongoing debilitating condition, if your horse is diagnosed with an ethmoid haematoma there is certainly hope that treatment will be successful and your horse will lead a normal healthy life.