Sinus disease is a common upper respiratory issue in many horses. What are the common problems and how do we treat them? What are the new options available to treat the common problems without extensive sinus surgery? 


Dr. Bell received his BSc (Microbiology/Immunology) from the University of Saskatchewan and his DVM from the Western College of Veterinary Medicine (WCVM). He completed an equine internship at Arizona Equine Medical and Surgical Centre. Dr. Bell followed the internship with a 3-year equine surgical residency at WCVM, where he is in his final year.


The most common presentation for a horse with a sinus problem is nasal discharge.  However, there are many causes of nasal discharge and not all relate to just a sinus issue. These can include upper respiratory tract infections (viral or bacterial), Strangles (Streptococcus equi equi bacteria), guttural pouch infections (fungal and bacterial), fractures of the facial bones, pneumonia or a number of possible sinus conditions including bacterial, fungal, viral, tooth root related, tumors, cysts, and ethmoid hematoma’s.

How can you tell them apart? A veterinary exam is key to differentiating one from another but briefly; Fever is generally associated with Strangles, viral infections, and lower respiratory tract issues. Foul odor is generally associated with sinus problems (tooth root abscesses), viral and bacterial URT infections, Guttural pouch bacterial infections and necrosis of tissue (trauma). Signs of depression and going off feed generally associated with Strangles, guttural pouch mycosis (fungal), some sinus issues (tooth root abscess, tumors), and pneumonia.

The color of the nasal discharge can tell you something about the origin of the condition.

Discharge Colour:
• Yellow = neutrophils + WBC
   - May be seen with Strangles, pneumonia, guttural pouch bacteria, sinus
• Green = eosinophils + WBC
   - May be seen with fungal, parasitic infections
   - May also indicate feed material mixed with purulent material
    • Difficulty swallowing etc….
• White = WBC
   - May be seen with viral/bacterial URT infections, sinus, guttural pouch issues and some       Strangles cases
• Red/pink = Red Blood Cells (hemorrhage) +/- WBC
   - May be seen with Guttural pouch mycosis (Fungus), ethmoid hematomas, fractures,       severe bacterial/fungal infections in sinuses

The focus of this paper will be on sinus conditions in the horse and how they are treated. Some sinus anatomy is necessary in order to understand the reason why there are so many sinus conditions that have the potential to affect your horse. The equine sinuses are very complex in there orientation and drainage. There are 6 paired paranasal sinuses; sphenopalatine, frontal, caudal maxillary, rostral maxillary, dorsal conchal, and ventral conchal. These communicated with each other through various openings between sinuses. The rostral maxillary and ventral conchal communicate only with each other. The upper cheek teeth roots are located in the rostral and caudal maxillary sinuses on both sides. All the sinuses are drained into the nose through a common opening called the nasomaxillary opening. This common opening results in a bottleneck effect in the draining process and leads to the potential for blockage and decreased or occluded drainage of the sinuses.

Sinusitis is inflammation of the sinus system and can be the result of two main causes:
1. Primary sinusitis
2. Secondary sinusitis – most commonly a tooth root abscess

In primary sinusitis, there is inflammation of the lining of the sinuses as a result of a migration of upper respiratory tract bacteria into the sinus system following an infection (common cold for horses). It usually affects younger horses as they are more predisposed to upper respiratory tract infections, however, it can be seen in horses of any age. The most common bacteria isolated in these cases are a Streptococcus species. This condition can result in many types of nasal discharge but the most common is a white discharge. The inflammation of the sinus lining results in blockage of the nasomaxillary opening (sinus drainage) and this causes pus to fill within the sinus. This increased amount of fluid develops high pressure within the sinus and can often result in sufficient pressure to cause facial bone deformity.

The condition can be diagnosed with endoscopy of the upper airway and radiographs of the sinuses to look for fluid. The treatment options for this condition range from minimally invasive to full sinus surgery. The traditional treatment is sinus lavage and systemic antibiotic treatment. The lavage or flushing of the sinus is performed through one or two small (4.5mm diameter) holes placed into the appropriate sinus area. The flush is done once a day for about 3 to 5 days. Clearing out the fluid and resolving the infection result in decreased inflammation and return to normal drainage.  If lavage fails due to large pieces of dried pus, then trephination (placing a larger hole) of the sinus, sinoscopic surgery (an endoscopic camera and instrument portal are made into the sinus to remove dried pus) or bone flap surgery of the sinus may be necessary. All of these more invasive procedures carry increased risk of bleeding and a longer recovery period.

A new technique has been recently developed to help with sinus drainage and potentially allow horses to avoid invasive sinus surgery. Based on a recent human technique for chronic sinusitis, an inflatable balloon is passed up the nose and placed into the nasomaxillary opening. The balloon is then inflated with saline to cause dilation of the opening and thus greatly increased drainage from the sinus. This increased diameter and drainage may allow for those large dried pus pieces within the sinus to be flushed out through the large opening and allow the horse to avoid sinus surgery for removal. The horse would still need lavage and antibiotics, but this could be performed by veterinarian on farm rather than having to bring the horse to a clinic.

In secondary sinusitis, there are several different types of problems which result in inflammation of the sinuses and blockage of sinus drainage or chronic sinus drainage. Tooth root abscesses are the most common of these problems. They are caused when bacteria enter into the tooth root either by spread through the blood stream or directly through a broken tooth. The abscess in the root ruptures into the sinuses and results in a sinusitis. These may have a white or yellow nasal discharge and the discharge will have a malodorous smell. Diagnosis is with radiographs of the skull and oral exam. Treatment is often removal of the offending tooth and packing of the tooth socket. Sinus lavage and antibiotics often follow removal and balloon sinuplasty have shown to increase drainage rates. In addition to tooth root abscesses; paranasal sinus cysts, ethmoid hematomas and neoplastic (tumors) can allow be causes for secondary sinusitis cases.

Cysts typically occur in younger horses (up to 4-5 year olds) and ethmoid hematoma’s and tumors can affect all horses, although usually horses older than 5 years old. The diagnosis with these problems often involves endoscopy of the upper airway, radiographs of the head and a full physical examination by your vet. Treatments vary from removal of the problem to medical treatment of the issue depending on location and severity.

In conclusion, nasal discharge can have multiple origins. A veterinary exam is important in determining the best course of action in all these cases. The most common sinus conditions are;
 –  Primary sinusitis
 –  Tooth root abscesses

The traditional treatments for sinus conditions are lavage and antibiotics +/- trephination or bone flap surgery depending on the severity and balloon sinuplasty represents a new technique to help treat horses with blocked sinus drainage.


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