Anal swelling and pain in female patients during menstruation may be due to several reasons. First, it is possible that pelvic congestion occurs, causing female patients to have anal cramping. Second, it may also be due to a slight pelvic inflammatory disease in female patients. When there is pelvic inflammatory disease, it can also lead to pelvic bleeding, which can cause anal cramping. Third, female patients may also have endometriosis, especially during menstruation when the ectopic endometrium will have a very obvious state of hyperplasia. If the location happens to be in the pelvis, it will also cause the patient to have anal cramping, which can be confirmed by ultrasound examination. In summary, all of the above are causes of anal cramping in female patients during menstruation. In addition, the production of fluid inside the pelvic cavity in female patients can also lead to anal cramping and pain.