At the 2008 American Association of Equine Practitioners convention, held Dec. 6-10 in San Diego, Calif., Terry Swanson, DVM, of Little Equine in Littleton, Colo., discussed the relatively rare condition of aortic-iliac thrombosis (TAI). He noted this condition can cause lameness, but the incidence in the United States is low. Damage to, and thrombus (blood clot) in, these large blood vessels might be caused by internal parasites.

The case Swanson presented was that of a 10-year-old Holsteiner gelding imported a few years prior to be used as a jumper. The horse had a right hind lameness for about a month following a fall into a fence, although it was thought that a subtle lameness might have been present before the fall. On exam, the horse demonstrated no lameness on any surface, no response to flexion tests or hoof tester exam, and no abnormal swellings in the limb. Under saddle, the horse was sound until about three minutes of exercise, then lameness progressively worsened until by seven minutes he was Grade 3 out of 5 lame. After a 15-minute rest he moved off sound until the lameness redeveloped after several minutes. Following a thorough clinical work-up that revealed nothing noteworthy, an ultrasound exam both rectally and along the inner gaskin identified the area of thrombus.

When conservative treatment with anti-parasitic drugs, non-steroidal anti-inflammatory drugs, isoxsuprine, and aspirin did not alleviate the problem, a Dutch surgeon familiar with this condition was consulted to perform thrombectomy surgery on the horse. Astrid B.M. Rijkenhuizen, DVM, PhD, Dipl. ECVS, DRVNA, of Utrecht University, has had a success rate of 60% in 15 cases to date using this procedure. The Holsteiner gelding has gone on to perform with no further related problems over the past four years. Swanson stressed the importance of being diligent in responding to a client’s concerns in investigating all possible treatment options, especially in difficult cases