Another source of abdominal pain during menses is the brain misinterpreting the source of the pain. The sensory nerves of the abdomen are not highly organized. Pain messages from the uterine cramps that occur during menses may "read" as pain in the abdomen by the brain.
Finally, an abnormal source of abdominal pain during menses may occur if endometriosis is present. Endometrial implants on the intestines grow and then bleed with menstrual flow. The presence of active bleeding in this tissue causes irritation and pain.