Cyclic changes in these cells can be associated with localized bleeding and resultant pain and damage. The exact reason for the development of endometriosis is unknown but there is a hereditary component. The main symptoms of endometriosis are pain and infertility, although not everyone gets these symptoms. The most common pain from endometriosis is pelvic pain which can be present at times other than the menstrual flow, although the pain is usually noted to worsen with the menses. Pain with intercourse is often present.
Endometriosis can cause rectal pain and bleeding, and premenstrual back pain as well.
Not all pelvic pain is caused by endometriosis, however. The mechanisms by which endometriosis causes infertility are unknown. Adhesions and destruction of the fallopian tubes which occurs with moderate to severe disease can explain the pain and infertility. Such pelvic distortion does not occur in mild endometriosis yet symptoms still may be severe. Women in affected families develop endometriosis at an earlier age and are more likely to have advanced disease.