Ultrasound of arterial and venous thrombosis
Feb 01, 2008
Thrombosis is a complication of many diseases in veterinary medicine.
Heart disease, protein-losing nephropathy and steroid therapy or hyperadrenocorticism can all predispose an animal to arterial or venous thrombi. Many of the systemic vessels involved are located in the abdomen and visible on abdominal ultrasound. We can identify thrombosis during an acute episode or as an incidental finding. Here are some of the features you might see:
Appearance of the thrombus
Location of the thrombus
The location of the thrombus determines whether it causes clinical signs. Arterial thrombi, such as in the aorta, can occlude blood flow to distal structures. Ischemia of the hind limbs is a common complication of aortic thrombosis, because the thrombus can occlude or extend down the iliac arteries.
Thrombi in the splenic veins are very common and may not cause any symptoms. These can be an incidental finding (Images 1 and 2), such as in this dog with lymphoma that had been treated with prednisone.
Tumors can cause physical obstruction of a vessel, usually in the caudal vena cava. Any tumor with a tributary joining the caudal vena cava can infiltrate the vessel and reach the systemic venous circulation.
How to evaluate thrombosis:
» Use color Doppler to look for acute thrombi.
» Evaluate the extent and location of visible thrombi.
» Check for peripheral flow with color Doppler.
» Look for evidence of neoplasia in the region.
» Check for sequelae of thrombosis such as ischemia of distal structures or ascites.
Dr. Zwingenberger is a veterinary radiologist at the University of California-Davis.