The guttural pouches are large, air-filled structures within the horse’s skull, in the throatlatch region. [1] These pouches can develop bacterial infections, fungal infections, or tympany, which is the excessive accumulation of air.

The most common symptoms of guttural pouch disease in horses are noisy breathing, nasal discharge, and swelling behind the jaw. Depending on the specific condition, treatment ranges from flushing the guttural pouches with saline to surgical intervention to remove the pouch’s contents.

Most diseases of the guttural pouches are not life-threatening. However, fungal infections within the guttural pouches can damage large arteries, causing horses to bleed profusely from their nostrils.

Horses experiencing a severe nosebleed require emergency medical attention as this condition can be fatal in some cases.

Guttural Pouch Anatomy in Horses

The guttural pouches are large extensions of the external auditory tubes that regulate pressure within the middle ear. [1] They are found at the back of the skull, about halfway between the base of the ear and the bottom of the jaw. [1]

The guttural pouches contain up to 500 mL (17.6 fluid ounces) of air in healthy horses. [1] They fill with air when the horse breathes in, and empty when the horse breathes out. [1]

Several large blood vessels and nerves run through the guttural pouches, including: [1]

  • Internal and external carotid arteries supplying the brain
  • Maxillary artery supplying the face
  • Nerves responsible for swallowing and tasting

The exact function of the guttural pouches is unknown, however research suggests the circulating air may cool blood supply flowing towards the brain. [1] Other proposed functions include a flotation device or a resonation chamber involved in producing a whinny. [2]

Diagnosis of Guttural Pouch Disease

Since the guttural pouches are confined within the horse’s skull, accessing them for examination or diagnosis requires specialized equipment. [2] Methods of examining the guttural pouches include: [2][3][4]

  • Endoscopy, which involves inserting a camera directly into the guttural pouch
  • X-rays of the head
  • CT or MRI imaging
  • Ultrasound

Endoscopy is the most common evaluation method for diagnosing guttural pouch diseases. [2][4]

Endoscopy is performed by a veterinarian, with the horse under sedation. The endoscope is inserted into the nostril, feeding the scope into the nasal cavity until it penetrates the opening to the guttural pouch. [2] Once in place, the endoscope can be further manipulated to examine the structures within the guttural pouch. [2]

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Guttural Pouch Mycosis

Guttural pouch mycosis is a fungal infection of the guttural pouches, resulting in fungal plaques lining the pouch walls. [1]

The most common fungus involves in guttural pouch mycosis is Aspergillus. [1][2] Horses acquire this infection when they inhale fungal spores from the environment, introducing the spores into the guttural pouches. [1] As the fungus proliferates, it produces plaques of fungal material that can cause damage to underlying tissues. [1]

Risk Factors

It is not known why only some horses in the same herd develop mycosis, but it may be related to arterial dilation within the guttural pouch. Dilated arteries may facilitate fungal growth more than normal arteries, but this phenomenon is not well understood. [1][2]

There are no known age, sex, or geographic risk factors for developing mycosis. [2]

Symptoms

Most horses show no signs of mycosis during mild to moderate infection. [1] As the fungal infection continues, the plaques invade deeper into the underlying tissues, resulting in symptoms of tissue damage. [1]

The most common symptom is profuse bleeding from the nose. [1] This occurs when the fungus invades one of the carotid arteries, weakening the vessel wall and leading to rupture. [1] In around 48% of cases, bleeding is severe enough to cause death. [1][2]

Other symptoms that may indicate a fungal infection in the guttural pouches include: [1][2]

  • Nasal discharge
  • Difficulty swallowing
  • Swelling behind the jaw
  • Paralysis of the facial muscles
  • Roaring“, noisy breathing during exercise

Difficulty swallowing, facial paralysis, and roaring arise from fungal damage to the nerves running through the guttural pouches. [2][3]

Horses bleeding profusely from the nostrils require urgent veterinary care. [1]

 

Treatment

Horses with active bleeding from the nose require emergency surgery to stop the bleeding. [1][2] These horses may also require blood transfusions to replace their lost blood.

After stopping the bleeding, the fungal infection typically resolves on its own as the fungus no longer has access to a nutrient-rich blood supply. [2]

Rarely, horses may be diagnosed with guttural pouch mycosis before developing nosebleeds. [2] In these cases, anti-fungal medication may be the first recommended treatment, particularly if there are no fungal plaques over the carotid arteries. [2]

Surgical Treatment

Surgery aims to cut off blood supply to the damaged artery, to prevent further bleeding. [2] Currently, the two most common surgical procedures are balloon occlusion or placing an embolization coil into the artery. [2] Surgeons access the guttural pouch through the back of the jaw, in the throatlatch region. [2]

Balloon Occlusion

Balloon occlusion involves feeding a balloon-tipped catheter into the damaged vessel. [2] Once the catheter is in place, the balloon tip is inflated to completely seal the vessel’s opening. [2] The surgeon sutures the free end of the catheter to the horse’s skin before closing the surgical site. [2]

The catheter is typically left in place for 7-10 days after the surgery, to allow a large blood clot to form in the damaged artery. [2] This blood clot prevents bleeding from recurring after the catheter is removed. [2]

Embolization Coil

Embolization coils are specialized stainless steel coils that a surgeon can guide into a blood vessel. [2] These coils provide a foundation for a blood clot to form around, speeding up blood clot stabilization. [2]

The surgeon inserts the delivery system for the coils into the damaged artery. [2] The delivery system injects the spring-shaped embolization coil into the artery. [2] A coil that is slightly larger than the artery is used so it pushes against the walls of the artery, ensuring a firm seal. [2]

The surgeon removes the delivery system and closes the surgical site. [2] Embolization coils can remain in the horse for the rest of their life, as the stainless steel becomes incorporated into the blood clot. [2]

Medical Treatment

Clearing a fungal infection can take months, as most combinations of anti-fungal medications are not very effective. [2] Medical treatment typically involves a combination of systemic (whole body) anti-fungal medications and medicated lavage (flushing) of the guttural pouches. [2]

To perform a guttural pouch flush, the veterinarian inserts a catheter into the opening of the guttural pouch within the nasal cavity. [2] Through the catheter, sterile saline containing antifungal medication is introduced and allowed to drain back out of the guttural pouch. [2]

Common antifungal products used for treating guttural pouch mycosis include: [5][6]

  • Nystatin powder
  • Povidone iodine
  • Hydrogen peroxide

If fungal plaques continue to grow, most veterinarians recommend surgery to remove the fungus’ access to nutrients and resolve the infection. [2] Horses managed medically have a high risk of bleeding out from nosebleeds, with one study showing 34% of horses treated without surgery dying from blood loss. [7]

Prognosis

With appropriate treatment, the prognosis of guttural pouch mycosis is favorable. [1] One study showed that embolization coils have an 84% survival rate, with 71% of horses returning to a performance career. [7] In this study, none of the horses had a recurrence of the fungal infection for up to 3 years after treatment. [7]

Horses that develop nerve damage due to the fungus irritating nerves running through the guttural pouch have a poorer prognosis. [2][5][8] Affected horses may recover some nerve function over time, allowing them to live a relatively normal life. [8]

In particular, horses with damage to the pharyngeal nerve, the nerve that controls movement of feed into the esophagus, have the poorest prognosis. [5][6][8] These horses often have difficulty swallowing and are prone to developing aspiration pneumonia if feed enters the lungs. [8]

Mildly affected horses may recover, however it can take up to 18 months of intensive care and vigilant monitoring for signs of pneumonia. [8]

Guttural Pouch Empyema

Guttural pouch empyema describes the accumulation of pus within the horse’s guttural pouch. [1]

This condition occurs due to upper respiratory tract bacterial infections, such as strangles. [1] Bacteria enter the guttural pouches and cause inflammation, forming pus and causing swelling of the guttural pouches. [1]

In almost 20% of cases, pus that accumulates in the guttural pouch hardens and forms rock-like structures called chondroids. [1][9]

These structures harbor bacteria and can irritate the guttural pouch lining, leading to continued inflammation and recurring episodes of empyema. [9] Chondroids require additional treatment measures to completely resolve symptoms and prevent infection from spreading to other horses. [9]

Symptoms

The most common symptom of empyema is nasal discharge from one or both nostrils. [1] Other symptoms result from swelling of the guttural pouches, and include: [1]

  • Pain in the area behind the jaw
  • Noisy breathing
  • Difficulty swallowing

Treatment

Treatment focuses on a combination of flushing the pus from the guttural pouches and antibiotics to resolve the infection. [1]

Most horses with empyema have a respiratory infection, so systemic (whole body) antibiotics are common in treatment protocols. [1][2]

To flush the pouches, the veterinarian sedates the horse and feeds a catheter through the nostril into the guttural pouch opening. [1] Sterile saline is injected into the pouches through the catheter, then drains when the horse lowers its head. [1] Some veterinarians may also add antibiotics to the saline to treat the area directly. [1][9]

Chondroid Removal

Chondroids can harbor large amounts of bacteria, making them a source of repeated infection and contagion to other horses. [1] Prompt removal of chondroids through flushing of the pouches is recommended to clear the individual horse’s infection and prevent widespread infection across the herd. [1]

Some veterinarians may add acetylcysteine, a medication that dissolves mucus, to the flush solution to break up the chondroids. [1][10]

Large chondroids may require surgical removal. [1][9] To achieve this, surgeons make an incision in the horse’s throatlatch region, just below the jugular vein. [1] This approach allows access to the guttural pouch for removal of the masses. [1]

Prognosis

Most horses make a full recovery from guttural pouch empyema. [1] Horses with empyema due to strangles typically require three negative bacterial tests before the horse can leave quarantine. [1]

Guttural Pouch Tympany

Guttural pouch tympany refers to accumulation of air within the pouches that does not dissipate when the horse breathes out. [1] This condition is most common in foals and develops within the first few weeks of life. [11]

Studies suggest that tympany may have genetic component in Arabian horses, however all breeds of horse can be affected. [1][11] Some studies report a higher incidence of tympany in fillies, however the reason for this sex predisposition is unknown. [11]

The underlying cause of tympany is unknown, but likely reflects a functional defect in the entry to the guttural pouch that allows air into the pouch but does not allow it to escape. [1]

Symptoms

The main symptom of tympany in horses is swelling behind the jaw. [1] Other symptoms can result if the swelling interferes with breathing or swallowing and include: [1]

  • Noisy breathing
  • Difficulty breathing
  • Difficulty swallowing
  • Nasal discharge

Some foals may develop aspiration pneumonia if swallowing difficulties allow food to enter the airways. [1]

Treatment

Treatment involves draining the air out of the guttural pouch to resolve the swelling. [1] The main treatment methods include: [1][2]

  • Placing a catheter in the guttural pouch opening to allow air out
  • Placing a needle through the skin to remove air by syringe
  • Surgical correction to widen the guttural pouch opening or create an alternative opening

Surgical correction is the most common treatment protocol for affected foals. [1][12] Symptoms frequently return after catheter or needle placement, and these treatments may have additional complications such as scarring or introducing bacteria into the guttural pouch, causing empyema. [12]

With surgical correction, most foals make a full recovery with few complications. [12] In some cases, the surgical site may scar or heal over, blocking the opening created by the surgeon. [12]

These foals require a second surgery to re-open the surgical site and allow air drainage. [12] Studies show that around 16-29% of foals require a second surgery to completely resolve symptoms. [11]

Most foals show no long-term effects from tympany into adulthood. [1] As adults, these foals can have successful performance careers. [11][12]

Summary

The guttural pouches are extensions of the auditory canals in horses and are involved in regulating air pressure within the horse’s skull.

  • The main diseases of the guttural pouches are bacterial infection, fungal infection, and tympany
  • Symptoms include noisy breathing, nasal discharge, and swelling behind the jaw
  • Most horses make a full recovery from guttural pouch diseases with appropriate treatment
  • Horses bleeding excessively from the nostrils require emergency medical attention, as these nosebleeds can be fatal

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References

  1. Reed. S. M. et al., Equine internal medicine, 3rd ed. St. Louis, Mo: Saunders Elsevier, 2010.
  2. Hardy. J. and Léveillé. R., Diseases of the Guttural Pouches. Veterinary Clinics of North America: Equine Practice. 2003. doi: 10.1016/S0749-0739(02)00070-6. View Summary
  3. Borges. A. S. and Watanabe. M. J., Guttural Pouch Diseases Causing Neurologic Dysfunction in the Horse. Veterinary Clinics of North America: Equine Practice. 2011. doi: 10.1016/j.cveq.2011.08.002. View Summary
  4. Thomas-Cancian. A. et al., Diagnostic Imaging of Diseases Affecting the Guttural Pouch. Veterinary Sciences. 2023. doi: 10.3390/vetsci10080525.
  5. Church. S. et al., Treatment of Guttural Pouch Mycosis. Equine Veterinary Journal. 1986. doi: 10.1111/j.2042-3306.1986.tb03654.x. View Summary
  6. Dobesova. O. et al., Guttural Pouch Mycosis in Horses: A Retrospective Study of 28 Cases. Veterinary Record. 2012. doi: 10.1136/vr.100700. View Summary
  7. Lepage. O. M. and Piccot-Crézollet. C., Transarterial Coil Embolisation in 31 Horses (1999-2002) with Guttural Pouch Mycosis: A 2-Year Follow-Up. Equine Veterinary Journal. 2010. doi: 10.2746/042516405774479960. View Summary
  8. Greet. T. R. C., Outcome of Treatment in 35 Cases of Guttural Pouch Mycosis. Equine Veterinary Journal. 1987. doi: 10.1111/j.2042-3306.1987.tb02649.x. View Summary
  9. Dixon. P. M. and James. O. A., Equine Guttural Pouch Empyema, Why Does It Become Chronic?. Equine Veterinary Education. 2018. doi: 10.1111/eve.12707.
  10. Cestari. H. et al., Non-Surgical Treatment of Guttural Pouch Empyema with Presence of Chondroids in a Filly. Acta Scientiae. Vet. 2020. https://seer.ufrgs.br/ActaScientiaeVeterinariae/article/view/100530 doi: 10.22456/1679-9216.100530.
  11. Blazyczek. I. et al., Retrospective Analysis of 50 Cases of Guttural Pouch Tmpany in Foals. Veterinary Record. 2004. doi: 10.1136/vr.154.9.261. View Summary
  12. Freeman. D. E., Guttural Pouch Tympany – a Rare and Difficult Disease. Equine Veterinary Education. 2006. doi: 10.1111/j.2042-3292.2006.tb00454.x.