Page 652 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Respir atory system: 3.2 Surgical conditions of the respir atory tr act 627

VetBooks.ir 3.59 3.60

Fig. 3.60 Intraoperative view of a large subepiglottic
Fig. 3.59 Oral endoscopic examination showing a cyst during surgical removal via a ventral
subepiglottic cyst. laryngotomy. (Photo courtesy Graham Munroe)

an oral approach, using a Gigli wire snare, passed It appears to be a response to exposure of the URT
using two Chambers metal uterine irrigation cath- to new antigens. The condition resolves with age.
eters welded together has been described, but the It is unusual for lymphoid hyperplasia to result in
tough subepiglottic mucosa makes this quite difficult. airway obstruction except in the most severe cases,
Alternatively, a radiofrequency snare can be used to although respiratory noise is a frequent finding.
transect the tough mucosa surrounding the cyst.
Finally, the cyst can be surgically excised via a lar- Aetiology/pathophysiology
yngotomy (Fig. 3.60). The mucosal defect is left to It is a normal response of the pharyngeal lymphoid
heal by secondary intention. Transendoscopic laser tissue to hypertrophy in response to exposure to
dissection is also possible, but the required plane of antigenic stimuli, including viruses, bacteria and
dissection is orthogonal to the endoscopic view, and other respiratory irritants such as dust and spores,
iatrogenic trauma to the epiglottis can result. which are increasingly confronted by a young horse
while travelling, entering training and mixing with
Prognosis its peers. The pharyngeal tissues respond by secret-
Prognosis is excellent following complete removal, ing mucus and local immunoglobulins. As the horse
as recurrence is rare. The outlook for return of and its immune system mature, the hypertrophy
normal pharyngeal function in cases of dorsal dis- resolves and the condition is rare after 5 years of age.
placement of the soft palate is also good. Dysphagia
and respiratory obstruction are usually prevented Clinical presentation
immediately. The most common reason for the detection of pha-
ryngeal lymphoid hyperplasia is as an incidental
PHARYNGEAL LYMPHOID HYPERPLASIA finding during a ‘routine’ endoscopy examination.
The majority of the time there is no interference
Definition/overview with the performance or health of the horse but, in
This is an extremely common condition of the young extensive and severe cases, there may be an abnor-
horse (<2 years old) and is considered a normal mal respiratory noise and possible effects on perfor-
developmental process rather than a genuine disease. mance due to airflow turbulence and/or reduction.