Chronic nasal discharge and labored breathing might indicate a guttural pouch infection.
T
he guttural pouch—located at the junction of the inner ear tube and the pharynx—can be a haven for bacteria and infection in horses. Guttural pouch infections are either introduced directly through the pharyngeal opening or by the lymphatic system. Accumulation of pus is considered to be a secondary, chronic, localized manifestation of a more general- ized respiratory infection, especially by Streptococcus equi. Typically, a horse with guttural pouch infections displays continued nasal discharge after recovery from streptococcal infection. Rupture of retropharyngeal abscesses—collections of pus at the back of the throat—into the guttural pouch is known to occur, suggesting that strangles or other upper- respiratory tract infections might have an important role in the development of guttural pouch infection in horses. Clinical signs of guttural pouch infection include intermit- tent nasal discharge that might worsen when the head is lowered, lymph node swelling, parotid gland inflammation, difficulty swallowing and labored breathing. The nasal dis- charge—generally non-odorous, white and opaque—can be from one or both nostrils, even if only one guttural pouch is affected. Signs of difficulty swallowing and labored breathing might intensify as the infected pouches distend. The dif- ferential diagnosis of guttural pouch infection should include other diseases with purulent nasal discharge, such as pneu- monia, sinus infection and upper-respiratory tract infection. Usually, an elevation in the total white blood cell counts
is observed, as well as fibrinogen, a coagulant. Those changes generally coincide with fever and clinical signs of strangles or primary guttural pouch infection. Analysis of fluid obtained from the guttural pouch often reveals a Streptococcus species. Many horses with pus collection in the guttural pouch, however, do not have a history of strangles, and it appears to occur by many of the same mechanisms as middle-ear infection—that is, fluid accumulates in the area and uncontrolled growth of bacteria normally results in inflammation and discharge.
The guttural pouch location
Guttural pouch infections should be considered in any horse with a chronic, nonresponsive nasal discharge. Diagnostic tools include radi- ography, endoscopy, and aspiration of fluid from the pouch.
Recognition of a fluid line or masses in the pouch on a radiograph supports the diagnosis of a guttural pouch infec- tion. Endoscopic examination permits identification of the affected pouch and evaluation of the fluid. Treatment of guttural pouch infection is complicated
by poor drainage from the affected pouch. In the normal horse, the pharyngeal opening of the guttural pouch is located above and in front of the floor of the pouch. There- fore, drainage can only be achieved by lowering the horse’s head. However, in horses with pus collection, lowering the head might not facilitate adequate drainage. Mucus membrane inflammation might result in swelling of the tissue around the opening of the pouch, further compromising normal drainage.
Choice of medical or surgi-
cal treatment depends on the duration and nature of the empyema. Antibiotic therapy might reduce the quantity of the nasal discharge, but relapse often follows cessa- tion of treatment. Early stages infection might respond to the daily lavage of the affected guttural pouch with saline antibiotic solutions injected through a catheter. Irrigating the guttural pouch with a catheter might result in the development of severe inflammatory changes in the guttural pouch. Consideration should be given to using nonirritating solutions to prevent an inflammatory response involving the cranial nerves. Treatment with oral, intramuscular or intravenous antibiotics and local lavage is successful, but the course of treatment might be prolonged. If the response to treatment is poor or secretions reaccumulate and empyema returns, surgical drainage of the guttural pouch should be consid- ered. Surgery is generally indicated when pus becomes thick or if chondroid—hard, dried pieces of pus—have formed. The prognosis for guttural pouch empyema is generally favorable if it is recognized promptly and treated appropriately.
By Tom Hutchins D.V.M., DABVP
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