Overground endoscopy in 311 Thoroughbred racehorses: findings and correlation to resting laryngeal function

To review a large number of equine overground endoscopy (OGE) examinations to determine the incidence of dynamic upper airway obstructions (DUAO); correlations were explored with laryngeal endoscopy findings at rest and abnormal exercising respiratory noise.

Retrospective analysis of horses presenting for OGE because of perceived poor performance and/or history of abnormal exercising respiratory noise between 2010 and 2014. Signalment, history and examination findings during resting laryngeal endoscopy and OGE were reviewed.

Of the total examinations, 311 were reviewed. One or more DUAO were found in 249/311 horses. From 210 males (colts and geldings), 121 had arytenoid cartilage collapse (ACC) and 111 had vocal fold collapse (VFC). From 101 females, 25 had intermittent dorsal displacement of the soft palate (DDSP). Resting laryngeal function grade 4 was found in 121/311 of the study population and 92/210 of males. An association was found between horses with lower resting arytenoid abduction ability to dynamic ACC and higher resting arytenoid abduction ability with DDSP. Abnormal exercising respiratory noise was positively associated with the presence of DUAO.

Multiple DUAO in association with abnormal exercising respiratory noise was a common finding in horses examined for poor performance. This study highlights the importance of OGE in accurately diagnosing the nature of DUAO associated with poor performance.