posted: 14/Feb/2017

We are aware of the commonly devastating effects of blood clots and aortic thromboembolism in our feline patients however less commonly we may encounter aortic thrombotic disease in dogs. Aortic thrombotic disease may arise from thromboembolism where a clot arises from a distant site (most commonly the heart), or aortic thrombosis where the clot forms in situ. In dogs aortic thrombosis is more common than aortic thromboembolism. Clinical signs are due to loss of blood flow to the caudal limbs resulting in limb paresis and paralysis with loss of femoral pulses, pain, cold extremities and pale or cyanotic pads often described as the ‘rule of P’s,’ paralysis, pulselessness, pain, poikilothermia and pallor. The onset of these clinical signs in dogs can differ significantly from cats due to difference in pathophysiology and the formation of the thrombus in situ rather than embolism. Clinical signs may present as acute or chronic and the severity of clinical signs may vary based on the degree of vascular occlusion present.

The majority of cases will have an underlying disease process which may precipitate thrombotic disease include protein losing nephropathy, protein losing enteropathy, diabetes mellitus, hypothyroidism, hyperadrenocorticism, immune-mediated thrombocytopenia, cardiac disease and neoplasia. However no concurrent condition may be identified as a predisposing factor for thrombus formation.

Recommendations for treatment of aortic thrombotic disease are not defined and proven therapy has not been identified. The mainstay treatment of aortic thrombosis is directed at limiting propagation of the thrombus and may include anticoagulant and platelet inhibition therapy such as aspirin, clopidogrel, heparin and warfarin. Thrombolytic treatment is less frequently undertaken than less aggressive therapy due to absence of proven benefit however options include medical, interventional radiology and surgical approaches such as systemic thrombolytic administration, direct thrombolytic administration and surgical thrombectomy.

Balloon catheterisation of aortic thrombosis is a procedure involving the use of a balloon catheter to push clots against the luminal wall in order to reestablish blood flow but does not lyse the clot. Identification and treatment of underlying disease processes should be taken where possible.

Prognosis for dogs with aortic thrombosis is more difficult to establish compared to cats with aortic thromboembolism due to large variation between patients in relation to etiology, onset and severity of clinical signs and concurrent conditions that may be present. 

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