Guttural pouch disorders

Guttural pouch empyema

Guttural pouch empyema, or pus in the guttural pouch, is frequently related to strangles (Streptococcus equi infection). Affected horses are often infectious. Drainage from the guttural pouch openings may be seen on endoscopy. Treatment generally involves lavage of the guttural pouch combined with systemic and/or local antimicrobials. Antibiotics alone are not usually sufficient. Retropharyngeal lymph node swelling or full guttural pouches can compress the pharynx (“strangling” the horse). Tracheotomy may be needed.

This radiograph shows a fluid line in the guttural pouch.

Clinical signs – bilateral purulent nasal discharge, fever, poor appetite, swollen lymph nodes

Guttural pouch chondroids

Chondroids develop when the purulent material from guttural pouch empyema desiccates. These “stones” of pus may need surgery for removal. NO agents have been found to dissolve the stones and many compounds lead to severe trauma to the guttural pouch. Chondroids generally have to be flushed out or removed manually. This is not an easy process. Surgery may be necessary but has lots of risks due to the related inflammation that occurs near all sorts of named arteries and nerves. There is no easy ventral drainage of the guttural pouch. As most animals don’t have guttural pouches, this is a horse thing.

Clinical signs – unilateral or bilateral purulent nasal discharge, often without other signs

Guttural pouch mycosis

Guttural pouch mycoses are fungal infections, generally involving Aspergillus fumigatus. This opportunistic fungus lives in the environment and attaches to an artery in the guttural pouch for nutrition. It can erode through the arterial wall, leading to bleeding (often severe). If the fungus is on an artery, surgical occlusion of the artery is the preferred therapy. This requires both proximal and distal occlusion of the artery due to the Circle of Willis . The Circle of Willis is a circle of arteries around the brain. This loop leads to the potential for blood flow from both ends of the artery. Due to access issues, a balloon or coils are used to block off the far end of the artery while a ligature is used on the artery outside of the pouch. If the fungus is on a bone or non-arterial structure, it can be scraped off or treated with topical antifungals. Due to the risk of fatal hemorrhage, those options are not recommended for fungal infections involving an artery. Antifungal agents are not required if surgery is used, as the fungus cannot live without the arterial oxygen supply. Once the artery is occluded, the fungus dies off.

Bilateral infections are possible. Horner’s syndrome can develop due to involvement of the vagosympathetic trunk. The infections can also lead to dysphagia as the fungus affects nerve function to the tongue and swallowing muscles. Typically, horses with swallowing issues have a very poor prognosis.

Clinical signs – unilateral or bilateral hemorrhagic nasal discharge; discharge may be intermittent and may be copious. Dysphagia and/or Horner’s syndrome are possible.

Basilar skull fractures

Hemorrhage can develop in both guttural pouches with trauma to the back of the skull and/or the basisphenoid bones. This is most common in young horses that flip over backwards and land on the basilar skull region. This disorder can be difficult to differentiate from guttural pouch mycoses on initial presentation. Many of these horses will also have neurological symptoms and air may be seen mixed with the soft tissue blood opacity on radiographs. CT examination may be useful to fully evaluate the extent of damage. Prognosis is generally poor. There really aren’t surgical options. Consider this a differential.

Clinical signs- bilateral hemorrhagic nasal discharge and/or neurological dysfunction

Guttural pouch tympany

Guttural pouch tympany is a non painful fluctuant swelling of one or both guttural pouches, particularly in Arab and German warmblood fillies. Air collects in the pouch as the opening operates as a one way valve rather than allowing bidirectional airflow. Respiratory distress is uncommon. Diagnosis is not difficult but it can be more challenging to determine if the disorder is unilateral or bilateral. On endoscopy, an abnormal guttural pouch opening is often evident. Medical treatment (NSAIDs) may resolve some cases. Surgery involves using a laser to create an opening either into the normal guttural pouch to allow air to exit the normal side or creating an opening into the pharynx. Prognosis is good if treated prior to the development of infection inside the pouch.

Clinical signs – nonpainful fluctuant swelling in the guttural pouch region

Temporohyoid osteopathy

Temporohyoid osteopathy (THO) is incompletely understood but involves proliferation of bone around the temporohyoid joint and can result in fusion of the joint between the stylohyoid bone and inner ear.  With movement of the head or tongue, pain results and the stylohyoid bone can fracture. Remodeling of the joint and/or bone can be seen radiographically and endoscopically. The remodeling is suspected to result from local (inner ear) infection. Damage to local nerves can also result in poor tear production, dry eye and corneal ulcers. Surgical treatment involves cutting the ceratohyoid bone in the hyoid apparatus to relieve pressure on the joint and stylohyoid bone. Cutting the ceratohyoid bone is much easier and much less dramatic than cutting the stylohyoid bone and has the same result of disconnecting tongue and inner ear. Horses can be affected bilaterally. Prognosis depends upon the degree of dysfunction identified prior to surgery.

Clinical signs: corneal ulcers, conjunctivitis, dysphagia