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The Ins and Outs of Your Horse’s Guttural Pouch


Pet Column for the week of April 30, 2012

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Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Andrea Lin
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Source - Dr. Pamela Wilkins
People who own horses have probably heard of the guttural pouch and the troubles associated with it. But what exactly are these guttural pouches, and why do horses have them?

According to Dr. Pamela Wilkins, who heads the equine medicine and surgery section at the University of Illinois Veterinary Teaching Hospital in Urbana, guttural pouches are not unique to equine species, though equines do have some of the largest. Certain species of rhinoceros, tapirs, bats, a South American forest mouse, and hyraxes also have guttural pouches.

“In horses, the guttural pouches are thought to regulate the temperature of blood arriving to the brain,” explains Dr. Wilkins. “Horses have no ‘rete mirabile’ – a network of small blood vessels that regulates heat in the blood going to the brain in other animals. Without a mechanism for heat regulation, horses could easily overheat their brains when they exercise.”

Horse anatomy supports this theory; the carotid arteries run through the pouches, which are located in the back of the throat and are connected to the tubes that link the ears and throat.

Dr. Wilkins explains that the most common diseases involving the guttural pouch are empyema (infections with bacteria that result in production of a lot of pus), fungal infections, and temporohyoid osteopathy. These diseases can have similar signs, namely, paralysis, choke, and bleeding. The signs arise because of the vital structures that pass through the guttural pouch; in addition to the internal and external carotid arteries, there are five cranial nerves separated from the guttural pouch by only a thin membrane.

“Bacterial infections can affect the pouches in much the same way people with sinus infections can get ear infections,” says Dr. Wilkins. The most commonly seen problem is guttural pouch empyema, when the pouches fill with pus from an infection, such as the bacterial disease strangles. To treat this, sometimes the pouches must be flushed and cleaned and the horse may be given antibiotics.

Guttural pouch mycosis, another frequent problem, is an infection caused by fungal organisms, most commonly Aspergillus. The infection forms as fungal plaques attach to the inside wall of the pouch over the internal carotid artery. Resulting damage to the wall and blood vessel leads to bleeding. Severe episodes can cause a horse to bleed to death. Treatment has both surgical and medical components. Antifungal medications may be used to kill the fungus, while surgery is used to block off the artery to prevent a fatal hemorrhage and “starve” the fungus.

The third most common disease is temporohyoid osteopathy, or THO. Hyoid bones are located in the throat around the epiglottis, which covers the opening to the trachea and the lungs during swallowing. (In humans, one of the hyoid bones forms the Adam’s apple.) The temporohyoid joint connects these hyoid bones to the skull.

In THO, the joint becomes immobilized and the hyoid bones thicken. Without movement in that joint, movement of the tongue creates enough pressure to fracture either the temporal or one of the hyoid bone. If this happens, facial paralysis and dizziness can follow within days due to associated nerve damage.

Because signs may not be easily differentiated among the common guttural pouch problems, veterinarians can use endoscopes to see inside the guttural pouch for both diagnostic and treatment purposes.

For more information about guttural pouches or equine health, contact your local equine veterinarian.