Objective   To establish a fusiform carotid aneurysm model in canine

investigate its long-term reliability with high-frequency ultrasonography (HFUS)

and evaluate its pathological features with light and transmission electron microscopy (TEM).    Methods   Ten canines were performed with microsurgical operation after general anesthesia. The fusiform carotid aneurysms model were constructed by bilaterally cutting off a segment of 1.5 cm external jugular vein with peel off tunica adventitia of vein and then the segment was anastomosed in end-to-end with carotid artery. HFUS was carried out in 2

4 and 12 weeks and pathological features were evaluated in 6

12 and 24 weeks (4 aneurysms of 2 canines for each time point) after surgical procedure. Meanwhile

the left 4 canines continue to observe until 24 months.     Results   All 10 dogs succeeded to survive and 20 fusiform carotid aneurysms were obtained successfully with a success ratio of 100%. HFUS clearly demonstrated that the eddy was observed in the cavity of fusiform aneurysm and the aneurysm

with intimal-thickening

atheroma plaque formation and calcification on the inner wall

grew in an expansile way and and had a tendency of spontaneous rupture in 12 weeks after operation. Statistical analysis showed these changes at different time points had significant difference (P0.05). Histopathologic study showed that the wall of aneurysms were mainly injured with stress hyperplasia at 6 and 12 weeks and then with adaptability remodeling at 24 weeks after the procedure under the effects of hemodynamics. But there was 1 case spontaneous ruptured and occluded at 12 months following surgery. Histopathological examination showed that hemorrhage in the aneurysmal wall

calcified fat plaques suddenly breaking away from the intima of distal stoma vessel wall

and aneurysmal cavity had be stuffed which leading to luminal occlusion and thrombosis. Observation in 24 months confirmed that the mechanism of hemodynamics and the pathological features of ruptured aneurysm were in accordance with those of human intracranial aneurysm.    Conclusion   This experimental model of canine fusiform carotid aneurysm with external jugular vein anastomosis is stable and repeatable

and its procedure is simple and rapid. This model is very useful for the study of the therapeutic technique of aneurysm and study of aneurysm pathogenesis.