Diagnosing Respiratory Tract Ulcers

"Respiratory disease is the second-leading cause of lost training in the Thoroughbred racehorse, second only to musculoskeletal injuries," said Jeff Blea, DVM, of the Southern California Equine Foundation in Arcadia, Calif., during the 2003 American Association of Equine Practitioners convention. "Endoscopy of the upper respiratory tract plays a vital role as a first-line diagnostic tool and can provide a wealth of information at the initial exam."

Blea, who worked with California practitioner Rick Arthur, DVM, on this paper, discussed in depth a technique for inspecting the epiglottis and subepiglottic area (beneath the epiglottis) using endoscopy in the standing horse, and discussed his findings among California Thoroughbreds using this procedure. From Jan. 1, 2000 to March 31, 2003, he diagnosed 33 horses in active training with subepiglottic lesions.

The cause of the problem is unknown, but he described the following possible factors: Mucosal irritation from dorsal displacement of the soft palate (DDSP), upper respiratory tract infection, trauma from swallowing foreign bodies (i.e., dirt), or dynamic epiglottic entrapment while training.

"Indications to evaluate this area include respiratory noise and a persistent cough, often along with poor performance," he said. "When the cough is observed while the horse is eating or when bitting up, this is pathognomonic (is indicative of a specific problem; in this case, subepiglottic ulceration). Other pharyngeal abnormalities on endoscopic examination of a horse with this problem might include persistent dorsal displacement of the soft palate, epiglottic abnormality, and/or a mucoid discharge in the pharynx."

Standard endoscopic examination might not reveal any subepiglottic problems, he said, because the epiglottis can easily conceal them. His technique for evaluating this elusive area requires a 65-cm-long malleable brass forked-end probe (5 mm wide, 12-mm fork width) inserted into one nostril to raise the epiglottis and look beneath it with an endoscope (preferably a videoendoscope) that is inserted into the other nostril. The procedure requires competent horse handlers, adequate sedation, a twitch, and topical anesthesia of the pharynx.

"All surfaces (of the brass probe) must be completely rounded and smoothed to prevent scratching any mucosal surfaces," he explained. "The brass material allows the probe to be bent to anatomical variations or the examiner's preferences."

Blea added that radiographing the area from the side with and without the probe elevating the epiglottis can give a practitioner additional information if a horse has a particularly bad ulcer in that area.

Case Evaluations and Treatment
Blea showed several cases with ulcerated subepiglottic tissue and sometimes ulcerations of the posterior soft palate, and he noted that excessive granulation can develop as well. "Posterior soft palate ulceration is commonly associated with subepiglottic abnormalities appearing as a 'kissing lesion' (where two lesions touch)," he said.

So what does one do about this problem when it's diagnosed? Although it's certainly not what the trainer and owner might prefer, "The most important treatment is to take the patient out of training," Blea stated.

He said rest alone might not heal the lesion, so antibiotic treatment is also important, especially with epiglottic swelling, tissue distortion, or tissue discoloration. "Long-term antibiotic therapy is often required to obtain complete healing and prevent recurrence," he said. Also, he noted that systemic steroidal or non-steroidal anti-inflammatory medication might be needed to reduce swelling, and throat flushes can help.

Prompt treatment is important, as Blea described scarring of the subepiglottic tissue during healing, possibly resulting in a deformed epiglottis after severe and/or chronic infection. Follow-up examination of the area is important to gauge treatment success.

"We do not know how frequently subepiglottic ulcerations occur in otherwise normal horses, but we hope to better characterize the lesion in the future," he concluded.

View with epiglottis in normal position View with epiglottis in normal position

(Left) This photo shows a standard view of the epiglottis obtained during routine endoscopic examination. (Right) This is the same horse during the same exam, but with the epiglottis elevated using a brass probe. A significant ulcerative lesion is very apparent with the epiglottis elevated, but would have been easily missed without this.


About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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