Aortic-Iliac Thrombosis Resulting in Ejaculatory Dysfunction in a Stallion

P. Ford, R. Turner, S. McDonnell, P. Sertich, and S. Bedford

Penn Vet Class 2007

            A 12-year-old Standardbred stallion was referred to the University of Pennsylvania from the University of Massachusetts for evaluation of weakness and discomfort during semen collection and specifically for ultrasonographic evaluation of the aorta and iliac arteries.  Observation of the stallion in hand and during semen collection attempts while mounted or on the ground revealed hind limb weakness, inadequate coupling and thrusting, instability and apparent pain.  Ultrasonography of the aortoiliac quadrification revealed irregular, heterogeneous masses occupying the caudal aorta, right external iliac, right and left internal iliac arteries consistent with aortic-iliac thrombosis (AIT).

AIT in horses is a reported cause of exercise-induced hind limb lameness and has been associated with ejaculatory dysfunction.  These problems can result in early retirement of breeding stallions and associated economic losses.  AIT can be idiopathic or can be caused by migrating larvae of Strongylus vulgaris, trauma, or endothelial damage due to turbulent blood flow and mechanical stresses that are assumed to occur during racing¹.

            If ultrasonography² is not used to identify the vascular occlusions causing the lameness and ejaculatory problems, AIT may remain undiagnosed.  If physical ejaculatory dysfunctions are left undiagnosed or untreated psychogenic ejaculatory dysfunction can develop.³  Although AIT cannot be cured, the symptoms affecting breeding capabilities can be alleviated and the breeding career of the stallion can be extended with proper diagnosis and treatment that includes nonsteroidal anti-inflammatory medication, aggressive anthelmintic administration, alternative collection techniques, and management changes designed to minimize discomfort to the stallion.  Supervised exercise programs may improve strength and stamina and stimulate collateral vascular growth.

1.         Maxie and Physick-Sheard.  Aortic Iliac Thrombosis in Horses.  Vet Pathol 1985;22:238-249.

2.         Reef et al.  Use of ultrasonography for the detection of aortic iliac thrombosis in horses.  JAVMA 1987;190:286-288.

3.         McDonnell.  Ejaculation, Physiology and Dysfunction.  Veterinary Clinics of North America: Equine Practice.  1992;8:57-70.