Guttural Pouch Tympany
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
- Chipmunk cheeks
- Distended nostrils
Other signs to watch for include:
- The esophagus also runs between the guttural pouches, and the foal may have trouble swallowing food. You may notice milk or other food coming out of the nostrils, or the foal may back off nursing. In this case, you will note that the mare has a large udder because the foal is no longer nursing adequately.
- If the guttural pouch tympany is chronic, the foal may actually develop pneumonia – aspiration pneumonia due to food going down the wrong tube. In this case, the foal may develop a cough, a fever, and a discharge that may look like pus, or be tinged with food, from both nostrils.
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:
- X-rays. X-rays of the guttural pouches can easily be taken in the field. The guttural pouches will be filled with air, which will appear to be a large black area. Accompanying infection or inflammation may also produce fluid in the pouches. If your foal has any signs of pneumonia, your veterinarian will usually choose to take an x-ray of the chest as well.
- Endoscopic exam. Your veterinarian will probably also choose to perform endoscopy of the guttural pouches. This procedure, which essentially allows the use of a small camera to look at the upper airways and the guttural pouches, can usually be performed with only very light sedation. Your veterinarian will often see a collapsed upper airway, due to the excessive air in the guttural pouches that is pressing down on the pharynx.
- Blood tests. Your veterinarian may also choose to do baseline bloodwork on your foal, to look for evidence of an infection.
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:
- If the guttural pouch tympany affects both sides (bilateral), then one of two options is possible. First, your veterinarian may choose to place a temporary catheter into the guttural pouch, giving the air a pathway for escape. The catheter usually stays in for 1-2 weeks. It seems to have the effect of enlarging the opening, because the tympany usually does not return. In other cases, it may be necessary to surgically enlarge the opening.
- If a surgical procedure is necessary, your veterinarian will usually also treat your foal with antibiotics. If your foal has a secondary pneumonia, your veterinarian will treat your foal with broad spectrum antibiotics, usually for two to four weeks at least, in addition to treating the guttural pouch tympany.
Watch for any return of swelling in the guttural pouch area, or any evidence of pneumonia, such as nasal discharge, coughing, or fever.