The morphologic characteristics of menstrual hemostasis in patients with unexplained menorrhagia.

The endometrium in uteri removed by hysterectomy in patients with unexplained menorrhagia was compared with the endometrium in patients with normal menstruation who had a hysterectomy for uterine prolapse. The vascular ultrastructure and hemostatic plug formation were examined from the late secretory phase throughout menstruation to day 9 of the proliferative phase of the menstrual cycle. Endothelial defects, with and without hemostatic plugs, were more common and were present longer in the endometrial blood vessels of patients with unexplained menorrhagia than in patients with normal menstruation. In normal menstruation, no vascular defects were observed after day 3 of the cycle, whereas vascular defects were observed up to day 9 in the blood vessels of patients with unexplained menorrhagia. These morphologic features are likely to play a major role in the increased menstrual bleeding in such patients without uterine pathologic findings.