Relationship Between Biomechanic Change Of Vessel Wall And Re-stenosis After Dilation Of Stenosed Vena Cava In Dogs: Comparative Study Using Different Imageological Modalities For Assessment

Objective To examine biomechanic change of vessel wall and re-stenosis after dilation of stenosed vena cava in dogs and to infer possible mechanisms of hypotonic luminal benign stenosis in an attempt to provide new evidence for clinical study of potential mechanisms of vena cava stenosis. Various imageological modalities were used to compare their respective advantages and disadvantages. Methods: Eighteen adult male dogs were equally divided into three groups. The vena cava stenosis model was established in all animals by the same method. The animals were anesthetized, whose four limbs were fixed and then an incision was made from the anterior abdomen to the posterior peritoneum to expose a 2cm segment of the stenosed vena cava directly. Postoperative DSA venography, CT, CT angiography and color Doppler ultrasonography of the vena cava were continued under anesthesia and venous blood pressure was monitored at the same time.After the animals were fed with normal chow for 2-5 weeks, the stenosed vena cava segments were balloon dilated to almost the normal size under DSA until obstruction of blood flow was eliminated. At 1, 3, and 5 weeks after the procedure, DSA, CT and color Doppler ultrasonography of the vena cava were performed again, and changes in venous blood pressure were monitored. The results of these imageological modalities were analyzed and respective advantages and disadvantages were compared.The animals were then sacrificed. The stenosed vena cava segments were separated and fixed for pathological study. Changes in cell composition of the stenosed segments and the VW of the anterior and posterior segments and different manifestations of the VW tunica intima and adventitia were observed.Results: The vena cava stenosis model was established successfully in all the experimental animals. The results of variance analysis showed significant differences in mean tension of the venous VW between the three groups, though the difference between the 3-week and 5-week groups was not significant. Pathological sections showed that re-stenosis of the venous lumen in the 5-week group, where the vessel wall was thickened, with inflammatory reaction of the tunica intima more predominant.DSA was good at displaying the length, morphology and branch circulation of the stenosed vena cava, especially in the 5-week group where there were abundant branches of circulation, but DSA was not so good in revealing thickness of the vessel wall and the structure of the tunica adventitia. Furthermore, spiral DSA was better than ordinary DSA in displaying space structure as was shown in three cases. Doppler ultrasound was good at observing blood flow and stenosis, but not so good in revealing branch circulation and macroscopic morphology. CT was good at revealing stenosis and change of the vessel wall, especially in the case of multi-plane and 3-D imageology.Conclusion: Comparative analysis of the imageological and pathological findings suggests that thickening of the vessel wall, especially change of the tunica adventitia, is the main factor of stenosis. We assume that local inflammation is the main cause for venous benign stenosis. Flexible use of various imageological modalities, especially combined use of CT, DSA and Doppler ultrasound, is preferable.