Anal pain during menstruation. And in the clinic is commonly caused by the following reasons: the first, because the uterus is in the posterior tilt and flexion position, stimulate to the rectum, will make menstruation anal pain, this situation if the attached position lying on the bed rest, anal pain tends to alleviate the situation; the second, because of the endometriosis caused by endometriosis, if the endometriosis foci in the rectum or in the vagina behind the fornix, the anus will also appear in the time of menstruation. The second is due to endometriosis, if the lesion of endometriosis is in the rectum or in the posterior vaginal fornix, anal cramps may also occur during menstruation. Therefore, it is recommended to find out the cause of the disease in the clinic. If endometriosis is the cause of the disease, in the clinic, through the gynecological examination, there will be nodules in the posterior vaginal fornix, and there is obvious tenderness, which can be basically diagnosed as the cause of endometriosis.