Anal distension during defecation during menstruation is mainly caused by pelvic congestion, edema and pelvic fluid retention during menstruation. Because pelvic congestion, edema and pelvic fluid will make the rectum uterine depression, congestion, edema, will stimulate the recto-anal nerve, there will be swelling and pain and swelling, with the cessation of menstruation, the symptoms can be gradually relieved. If the swelling and pain is obvious and persistent, you need to go to the hospital in time to avoid the occurrence of uterorectal fistula, the more common is that women suffer from hemorrhoids caused by anal swelling and pain, most of the women usually have the symptom of anal discomfort. Avoid tub baths and sitz baths during menstruation to avoid bringing pathogenic bacteria from the vulva and the perianal area into the vagina, which can lead to infections of the reproductive system, and avoid overwork.