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Keywords:

  • horse;
  • dynamic overground endoscopy;
  • Thoroughbred yearling;
  • upper respiratory tract;
  • laryngeal function;
  • intermittent dorsal displacement of the soft palate

Summary

Reasons for performing the study

Endoscopic examination of Thoroughbred (TB) yearlings is performed routinely to determine the suitability of horses for racing and to ensure that the conditions of sale are satisfied. However, previous research has demonstrated that resting endoscopic examination can be inaccurate in the diagnosis of functional pathology of the upper portion of the respiratory tract (URT).

Objectives

To investigate the feasibility of performing dynamic overground endoscopy in a group of TB yearlings and to compare the results of resting and dynamic endoscopic examination of the URT.

Study design

Prospective cohort study.

Methods

Resting (pre- and post exercise) and exercising endoscopy was performed on 57 TB yearlings at a single training yard. Observed abnormalities were recorded and graded. The results of resting and dynamic examination were compared.

Results

Dynamic overground endoscopy was well tolerated and was performed with few complications. Laryngeal asymmetry (29 cases) was the most common abnormality identified at rest, while intermittent dorsal displacement of the soft palate (IDDSP; 19 cases) was the most common at exercise. Significant variation in laryngeal function and variation in the occurrence of IDDSP was noted between examinations. Other potentially significant pathology that was not noted at rest but was present during exercise included collapse of the apex of the corniculate process, pharyngeal collapse and cricotracheal ligament collapse. The occurrence of IDDSP at exercise was significantly associated with epiglottic structure grade>2 and a recent history of respiratory tract infection.

Conclusions

Dynamic overground endoscopy is safe and potentially useful when assessing URT function in TB yearlings. Significant variations in the results of endoscopy at rest and during exercise were identified, which indicate that resting endoscopy may not be sufficient to predict the occurrence of pathology during exercise.

Potential relevance

Dynamic overground endoscopic examination could be considered a suitable means of assessing URT function in TB yearlings and may provide additional pertinent information to that obtained during standard resting examination.