Bit & Bridle

Equine Guttural Pouch Tympany

Other Names

  • Guttural pouch distension
  • Pneumoguttural pouch
  • Pharyngeal tympany in foals

What is Equine Guttural Pouch Tympany?

The guttural pouches are large, paired air-filled extensions of the Eustachian tubes unique to the horse and a small number of other odd-toed ungulates. Each pouch is located beneath the base of the skull and communicates with the nasopharynx via a slit-like ostium (opening) in the pharyngeal wall. Equine Guttural Pouch Tympany is a condition in which one or both guttural pouches become abnormally distended with air due to dysfunction of this ostium — specifically, the formation of a mucosal flap or plica that acts as a one-way valve, allowing air to enter the pouch during breathing but preventing its exit.

The condition most commonly affects young foals, typically within the first few weeks to months of life, though it can occasionally occur in older animals. Unilateral tympany (one pouch) is more common than bilateral involvement, and fillies appear to be overrepresented in some studies, though the reason for this is not fully established.

Causes

The primary mechanism is functional obstruction at the pharyngeal ostium of the guttural pouch. The most widely accepted explanation is that a redundant fold of the medial lamina of the guttural pouch creates a valve-like mechanism that traps air during the negative pressure created by respiration or swallowing. Contributing factors may include:

  • Abnormal conformation of the pharyngeal opening
  • Inflammation of the pharyngeal mucosa — secondary to upper respiratory infections or strangles — causing mucosal swelling that obstructs the ostium
  • Abnormal cartilage of the Eustachian tube orifice

A hereditary predisposition has been suggested in some breeds, but this has not been definitively established.

Symptoms and Signs

  • Non-painful, fluctuant (air-filled) swelling in the parotid region (behind the jaw and below the ear) on the affected side
  • Nasal discharge — typically bilateral even when tympany is unilateral, as the pouch communicates with the nasopharynx
  • Respiratory noise during exercise or at rest in more severe cases
  • Dysphagia (difficulty swallowing) if the distended pouch compresses the pharynx
  • Aspiration pneumonia — in severe or prolonged cases where swallowing is impaired, milk or feed may enter the airway
  • Nasal regurgitation of milk in young foals
  • Respiratory distress if bilateral distension severely compromises the airway

Diagnosis

  • Clinical examination: The characteristic non-painful, air-filled swelling in the parotid area is the primary diagnostic feature. Palpation reveals a tympanic (drum-like) quality on percussion.
  • Endoscopy: Nasopharyngeal endoscopy is the definitive diagnostic and planning tool. It allows direct visualisation of the guttural pouch ostia, assessment of the degree of distension, identification of the offending mucosal fold, and evaluation of the contralateral pouch. Endoscopy also allows assessment for secondary changes such as mucosal inflammation or empyema.
  • Radiography: Lateral skull radiographs confirm air distension of the guttural pouch and help assess the extent of bilateral involvement.
  • Ultrasonography: Can confirm the air-filled nature of the swelling and assess for any fluid component.

Treatment

Definitive treatment requires surgical correction of the abnormal ostium:

  • Endoscopic laser ablation: The treatment of choice in most modern equine referral centres. A diode laser is used endoscopically to ablate (destroy) the obstructing mucosal fold, restoring normal airflow through the ostium. This procedure can be performed under standing sedation in many cases and carries a good success rate.
  • Fenestration (Viborg’s triangle approach): A surgical opening is made through the floor of the guttural pouch into the contralateral pouch, creating a common chamber. This was a traditional approach and remains effective but is more invasive.
  • Temporary drainage: Placement of a catheter or tube through the nostril into the affected pouch provides immediate relief and may be used as a temporary measure before definitive surgery, particularly in young foals with respiratory compromise.
  • Management of secondary aspiration pneumonia: If aspiration has occurred, systemic antibiotics and supportive care are required.

Referral to an equine surgical facility is recommended for definitive treatment. The British Equine Veterinary Association (BEVA) can assist in identifying appropriate referral centres.

Prevention

There is no established preventive measure for guttural pouch tympany as it is primarily a developmental or congenital condition. Prompt treatment of pharyngeal infections in young foals may reduce the risk of secondary inflammatory obstruction of the guttural pouch ostium.

Prognosis

The prognosis following surgical treatment is generally good to excellent for uncomplicated cases. Endoscopic laser ablation has a high success rate, and recurrence is uncommon. Cases complicated by aspiration pneumonia require more prolonged treatment and carry a more guarded prognosis. Bilateral severe tympany with respiratory compromise is an emergency and must be addressed promptly to prevent fatal airway obstruction.

When to Call the Vet

Contact your vet promptly if a young foal:

  • Develops a soft, non-painful swelling in the parotid/retromandibular region
  • Shows nasal discharge that began in the first weeks of life
  • Appears to have difficulty swallowing or regurgitates milk through the nose
  • Shows any signs of respiratory distress or abnormal breathing noise

Frequently Asked Questions

Is guttural pouch tympany painful for the foal?

The swelling itself is generally not painful. However, if the distension is severe enough to compress the pharynx and cause dysphagia, the foal may show signs of discomfort when swallowing. Secondary aspiration pneumonia causes significant illness and discomfort.

Can guttural pouch tympany resolve without treatment?

Mild cases occasionally partially resolve spontaneously if the cause is inflammatory rather than structural. However, true structural obstruction of the ostium requires surgical correction and does not resolve on its own. Waiting without treatment risks worsening distension, aspiration pneumonia, and respiratory compromise.

What other guttural pouch diseases should owners be aware of?

The guttural pouches can be affected by several conditions in addition to tympany. Strangles (caused by Streptococcus equi) can cause guttural pouch empyema and chondroids (inspissated pus) that may require endoscopic flushing or surgical drainage. Mycotic guttural pouch infection (fungal plaques) can erode major blood vessels in the pouch, causing life-threatening haemorrhage.

At what age should guttural pouch tympany be treated?

Treatment should generally be performed as early as practicable once the diagnosis is confirmed, particularly if the foal is showing signs of respiratory difficulty, dysphagia, or nasal regurgitation. There is no benefit to delay, and early intervention reduces the risk of secondary complications.