THROMBOSIS OF THE POSTERIOR AORTA AND OE ITS BRANCHES 947 



VII.— THROMBOSIS OF THE POSTERIOR AORTA AND OF ITS 

 BRANCHES. 



Arteritis followed by partial or complete obstruction of the 

 lumen, may be caused by emboli, infection, sclerostomes, or by any 

 injury in which the inflammatory process involves the arterial walls. 

 Cases arising in this way, though probably not uncommon, are seldom 

 recognised during life. Partial or complete thrombosis of the posterior 

 aorta or of the iliac arteries frequently occurs in horses, and occasionally 

 a similar condition may be found affecting the brachial trunk, but 

 the cause in either case remains undiscovered. In some instances 

 there is a history of antecedent infectious disease (strangles, influenza), 

 but the connection between systemic disease and the occurrence of 

 aortic thrombosis waits explanation. 



Stoppage of small vessels near the femoral or pelvic arteries by 

 emboli of small diameter may produce no serious results, but where 

 large vessels are plugged, the muscles served by them, no longer 

 receiving the quantity of blood necessary for their functional activity, 

 are incapable of sustaining severe exertion, lameness appears, and the 

 horse comes to a standstill, from paralysis of the affected muscles. 



Whilst the animal is at rest circulation is maintained by collateral 

 vessels, and it is only on movement that symptoms develop. The time 

 of their appearance depends on the degree of obstruction in the vessels 

 and the intensity of the muscular action. When obstruction is partial, 

 or the vessels are small, the animal may go several hundred yards, 

 even at a fast pace, before lameness appears, and the symptoms vary 

 in character according to the muscles involved, but thrombosis of 

 large vessels is followed by symptoms of extensive muscular inability 

 after even three to five minutes' trotting. A few minutes' rest 

 produces an apparently perfect recovery. The intermittent lameness 

 thus produced is quite distinctive. Thrombi extending to the aorta 

 sometimes prove fatal, as shown by many reported cases. 



A remount showed oedematous swelling and inability to stand, 

 first in one hind limb and, on the following day, in the other. On 

 the second night it died, and on post-mortem examination the posterior 

 aorta was found completely thrombosed at its point of bifurcation. 

 The thrombus contained a specimen of Sclerostomum equinum. 

 Cases of rupture of the posterior aorta and of thrombosis of the iliac 

 arteries are described at length in Cadiot and Dollar's " Clinical 

 Veterinary Medicine and Surgery." In Rutherford's case the 

 posterior aorta, right external and internal iliacs, and left internal 

 iliac were all thrombosed. 



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