Abstract:
Upper airway endoscopy at rest has been the diagnostic method of choice for equine upper
respiratory tract (URT) conditions. Development of high-speed treadmill endoscopy improved
the sensitivity of URT endoscopy by allowing observation of the horse’s nasopharynx and
larynx during exercise. However, treadmill exercise may not always accurately represent
the horse’s normal exercise as track surface, rider, tack and environmental variables are
altered. Recently, the development of dynamic overground endoscopy (DOE) has addressed
some of these shortcomings. A retrospective study was undertaken to describe the URT
abnormalities detected during DOE in racehorses presenting with poor performance and/
or abnormal respiratory noise. Patient records of Thoroughbred racehorses undergoing DOE
from November 2011 to August 2012 were reviewed. Data collected included signalment,
primary complaint, distance exercised, maximum speed and dynamic airway abnormalities
detected. Fifty-two horses underwent DOE for investigation of poor performance and/or
abnormal respiratory noise. The main abnormalities detected included axial deviation of the
aryepiglottic folds (40%), vocal cord collapse (35%), abnormal arytenoid function (33%) and
dorsal displacement of the soft palate (25%). A total of 40 horses were diagnosed with one or
more abnormalities of the URT (77%). Fifteen horses (29%) had a single abnormality and 25
horses (48%) had multiple abnormalities. This study showed that DOE is a useful technique for
investigating dynamic disorders of the URT in racehorses in South Africa. The total number
and type of dynamic pathological conditions were comparable with those identified in similar
populations in other geographical locations.
