Case reveal » Veterinary Diagnostic Imaging » College of Veterinary Medicine

Bilaterally, the guttural pouches are diffusely moderately to severely gas dilated (green arrows). Ventrally within one of the guttural pouches (indistunguichable laterality), a small amount of gravity-dependent and homogeneously soft tissue opaque material forming a fluid-line at the gas interface is also identified (blue arrows).

Conclusions:

The thoracic radiographs were taken to screen for aspiration pneumonia.
The patient underwent a partial plicectomy (resection of a portion of a plica) and recovered without complications.

Guttural pouch tympany (GPT) is a rare but clinically significant condition affecting young horses, characterized by abnormal distention of one or both guttural pouches due to trapped air. The guttural pouch is a unique anatomical structure in equids, representing an air-filled diverticulum of the auditory tube. GPT typically presents in foals and young horses, with a notable predisposition in fillies (McCue et al.).

The precise cause of GPT remains uncertain, but the most widely accepted theory involves a congenital or acquired defect in the mucosal flap at the pharyngeal orifice of the eustachian tube. This flap may function as a one-way valve, allowing air to enter the guttural pouch during swallowing but preventing its exit, leading to progressive distention. The condition can be unilateral or bilateral and may result in compression of adjacent structures, including the nasopharynx, larynx, and contralateral guttural pouch.

Clinical signs include non-painful swelling in the parotid region, abnormal respiratory noise, nasal discharge, dyspnea, and in severe cases, dysphagia and aspiration pneumonia.

Radiography is the primary imaging modality used to diagnose GPT and is particularly valuable due to the air-filled nature of the guttural pouch, which provides excellent contrast. On lateral radiographic views, the affected guttural pouch appears markedly distended, often extending caudally beyond the atlas. The caudal border of the pouch is excessively rounded, and the ventral border may be displaced ventrally, compressing the airways.

In bilateral cases, the distention may appear symmetrical, complicating the differentiation between unilateral and bilateral involvement. Ventrodorsal views can aid in assessing the extent of distention and help distinguish between sides, although superimposition of bony structures may limit their utility.

Endoscopic examination complements radiography by allowing direct visualization of the pharyngeal orifice and mucosal flap, which may protrude into the pharynx and reduce airway size.

Surgical intervention is the mainstay of treatment for GPT. The most commonly employed procedures include:
1. Fenestration of the median septum between the guttural pouches, allowing air to escape from the affected side into the normal pouch and exit through its pharyngeal orifice.
2. Resection of the mucosal flap at the pharyngeal orifice to eliminate the one-way valve mechanism.

In a retrospective study of 15 cases, horses treated with both fenestration and flap resection had a slightly lower recurrence rate (29%) compared to those treated with fenestration alone (33%). Long-term outcomes were generally favorable, with most horses recovering fully and some returning to athletic performance (Judy et al.).

Advanced techniques such as laser fenestration via endoscopy have been proposed to reduce hospitalization time and minimize surgical complications, including cranial nerve damage (Judy et al.).

The prognosis for horses with uncomplicated GPT is generally good. Complications such as pneumonia or dysphagia may worsen outcomes, particularly if aspiration occurs. Early diagnosis and appropriate surgical intervention are critical to prevent secondary complications and ensure a successful recovery (Thomas-Cancian et al.).

Judy, Carter E., M. Keith Chaffin, and Noah D. Cohen. “Empyema of the guttural pouch (auditory tube diverticulum) in horses: 91 cases (1977–1997).” Journal of the American Veterinary Medical Association 215.11 (1999): 1666-1670.
Thomas-Cancian, Aurélie, et al. “Diagnostic imaging of diseases affecting the guttural pouch.” Veterinary Sciences10.8 (2023): 525.
McCue, Patrick M., David E. Freeman, and William J. Donawick. “Guttural pouch tympany: 15 cases (1977–1986).” Journal of the American Veterinary Medical Association194.12 (1989): 1761-1763.