[The effect of IUD on endometrial blood vessels--correlation between vascular changes and bleeding]

In order to examine the causes of endometrial bleeding following IUD insertion, 22 samples of endometrium from women with an IUD in place for between 1-20 years or more and 10 cases of endometrium without an IUD and with normal menstrual cycles as controls were studied. The quantitative histologic method was utilized to demonstrate the correlation between vascular changes and clinical bleeding. The results indicate that the concentration and expansion of microvascularity, especially the capillary, venule, and venous sinus, increased significantly in most of the IUD-exposed endometriums (75%) as compared with controls (p0.01). The remarkable changes in vessels correlated with clinical bleeding were increased density, obvious dilatation, defect, and rupture of the superficial venous sinus. Mechanical damage, degeneration, necrosis, and denudation of surface endometrium exposed to the IUD could be the direct cause of clinical bleeding.