Alar fold resection in 25 horses: Clinical findings and effect on racing performance and airway mechanics (1998-2013).

OBJECTIVE: To report clinical findings and performance in horses in which alar fold collapse (AFC) had been diagnosed and surgically treated and to assess form and degree of respiratory obstruction.

STUDY DESIGN: Retrospective case series.

ANIMALS: Twenty-one standardbreds, 2 coldblooded trotter racehorses, 1 thoroughbred, and 1 Icelandic horse.

METHODS: Alar fold collapse was diagnosed on the basis of continuous abnormal expiratory flutter noise coinciding with filling of the false nostrils during exercise on a high-speed treadmill that was alleviated by suturing the alar folds (AF) temporarily in a dorsal position. In 5 cases, nasopharyngeal airway pressures were assessed. Performance after complete, bilateral AF resection was assessed by reviewing career race records and by owner or trainer telephone interviews.

RESULTS: Horses presented because of poor performance, abnormal respiratory noise, or both. Additional dynamic disorders were identified in 12 of 21 standardbreds (intermittent dorsal displacement of the soft palate: n = 10; collapse of the roof of the nasopharynx: n = 2). Expiratory nasopharyngeal pressures seemed elevated in horses with AFC (range, +10.8 to +21.8 cm H2 O) compared with normal reference values. Dorsal fixation as well as complete surgical resection of the AF improved expiratory nasopharyngeal pressures to reported normal levels. At a mean of 68 months (range, 7-121) follow-up, 20 of 25 horses had competed after surgery, and 13 of 17 of the harness racehorses had established or improved their kilometer racing time marks.

CONCLUSION: Alar fold collapse caused mild to moderate expiratory obstruction and may have contributed to secondary nasopharyngeal collapse in this population.

CLINICAL SIGNIFICANCE: Complete surgical resection seems effective for treating AFC. Nasopharyngeal pressure measurement is a potential tool for confirming the diagnosis of AFC.