ObjectiveTo observe the ultrastructural changes of vasa vasorum endothelial cells in the walls of the great saphenous vein and splenic vein, and to evaluate the effect of high hydrostatic pressure and hypoxia upon vasa vasorum endothelial cells. MethodsThirty-four varicose great saphenous vein samples and splenic vein samples with portal hypertension were obtained, and the same number of normal great saphenous vein and splenic vein were used as the control groups. Semi-thin sections stained with HE staining vasa vasorum of the adventitia in great saphenous vein and splenic vein were observed for light microscopy. Samples were made into ultrathin-slices again. The ultrastructural changes of endothelial cells were observed under transmission electron microscopy. ResultsIn varicose great saphenous veins and diseased splenic veins, the nuclear architecture of endothelial cells in vasa vasorum were integrity and the distribution of chromatin were normal. In some mitochondria, the trachychromatic groundplasm, undefined and ruptured cristae were found. ConclusionUnder high hydrostatic pressure and hypoxia conditions, the ultrastructure of vasa vasorum endothelial cells between the great saphenous vein and the splenic vein may appear remodeling phenomenon, and both changes are similar.