Morphologic studies on IUD-induced metrorrhagia. II. Surface changes of the endometrium and microscopic localization of bleeding sites.

Surface changes were extensively studied by light and electron microscopy in human endometrium exposed to IUD's. A wide variety of alterations in the covering epithelium and its basal lamina (basement membrane) was observed. These ranged from essentially no alteration to a covering basement membrane completely denuded of its epithelium. Erosions or discontinuities of the surface basement membrane were uncommon, and when they occurred were most often associated with extrusion of fluid and cellular elements from the stroma into the uterine lumen. Metrorrhagia associated with IUDs probably results from two basic types of hemorrhage through the endometrial surface. Tissue adjacent to the IUD with interstitial hemorrhage bleed into the uterine cavity by (1) red cell transmigration through surface membranes (surface epithelium and its basal lamina), and (2) high interstitial pressure breaks in these same membranes.