The guttural pouches are only found in horses and their cousins, such as zebras and donkeys. The guttural pouches are rather splendid outpouchings of the eustachian tubes, the connection between the middle ear and the back of the oral cavity responsible for equilibrating pressures between the ear and our outside surroundings.
The gutteral pouches are framed by the base of the skull at the top, the pharynx and esophagus at the bottom, and the salivary glands and mandible on the sides. There is a slit-like opening from each gutteral pouch into the pharynx that is hard to see, and even harder to open for examination or drainage purposes.
Both guttural pouches are divided into two separate compartments by the stylohyoid bone. The one closer to the body's midline, called the medial compartment, contains many different nerves and arteries, including the internal and external carotid arteries, five cranial nerves, a few lymph nodes and some delicate bones and joints. This makes diagnosis and treatment of gutteral pouch problems difficult.
The guttural pouches are lined with the same respiratory epithelium, or tissue, that lines the upper airway. This means that the guttural pouch can be affected by viruses and infections that affect other portions of the upper airway.
In the horse, the guttural pouch can be seen only by endoscopic examination. Two flaps, one on each side, are visible just before the voicebox (larynx). These flaps ordinarily do not allow any air into the guttural pouches.
Gutteral Pouch Tympany
Guttural pouch tympany simply refers to distention of the guttural pouches with air. It does not appear to cause the horse any pain, but if the distention involves both sides, it can cause respiratory distress.
Guttural pouch tympany usually occurs in foals younger than 6 months, but can occasionally show up in horses as old as one and a half years. It can be treated with various levels of invasiveness and some cases require surgery. The prognosis for guttural pouch tympany tends to be quite good.
What to Watch For
Other signs to watch for include:
Your veterinarian may suspect guttural pouch tympany just by looking at the foal. The distinctive outward bulging of the guttural pouches is often a dead giveaway. Other tests include:
If the guttural pouch tympany only affects one side (unilateral), then it may be possible to open the affected guttural pouch into the unaffected one, thus letting the air escape through the side that functions normally. In some situations this can be done under heavy sedation using an endoscope and a small biopsy instrument that fits through a channel in the endoscopes. In some situations, surgery is necessary. Other treatment may include:
Watch for any return of swelling in the guttural pouch area, or any evidence of pneumonia, such as nasal discharge, coughing, or fever.