Unusual cause of exercise intolerance and bunny-hopping gait in an 8 year old male neutered collie mix

Clinical History

Clinical presentation was for a 4-month history of exercise intolerance. Previously the dog was very active and able to perform 60-120 minutes of strenuous activity without any problems. Recently the dog stopped playing with the two other dogs in the household. Within a few minutes of beginning exercise his head carriage lowered, his ears became flattened, and he rapidly started to pant and salivate. The pelvic limbs tucked up and bunny hopping was noted until finally he would sit down. Pain was not described although, following a period of rest, the dog would appear stiff.

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Physical, Orthopedic and Neurological Examinations

With the exception of mild muscle atrophy in the quadriceps and hamstring muscle groups, no specific abnormalities were identified.

Diagnostic Tests

CBC - Minimal elevations of packed cell volume and hemoglobin
Manual platelets - Mild thrombocytopenia
Chemistry Panel - Mild to moderate elevations of AST and CK activities on two separate occasions

Acetylcholine receptor antibody - within the reference range
Rheumatoid Factor - negative
ANA - negative
Total T4 - within reference range
TSH - within reference range

Infectious disease titers - negative

Radiographs of the pelvic limbs, lumbosacral joint, thorax and abdomen all normal
Joint taps - normal
EMG of multiple muscle groups - no spontaneous activity found

Treatments and Outcome

Treatments included a short course of corticosteroids and a NSAID trial. No improvement was noted with either of these treatments. Doppler ultrasound discovered a large thrombus in the aorta extending from just caudal to the renal arteries into the external iliac arteries. A specific underlying cause for this abnormal clotting activity was not identified. In the dog, heart disease, protein losing diseases including nephropathy and enteropathy leading to a hypercoagulable state and Cushing's syndrome should be considered. This case demonstrates the importance of including clotting disorders in cases of progressive exercise intolerance and pelvic limb weakness in dogs.

References

Goncalves R, Penderis J, Chang P et al. Clinical and neurological characteristics of aortic thromboembolism in dogs. J Small Anim Pract 2008;49: 178-184.

Lake-Bakaar GA, Johnson EG, Griffiths LG. Aortic thrombosis in dogs: 31 cases (2000-2010) J Am Vet Med Assoc 2012;241:910-915.