Endometriosis: aetiology, pathogenesis and treatment

Endometriosis, which may be defined as the presence and proliferation of endometrial tissue outside the uterine cavity, causes pain and infertility for millions of women worldwide. Studies suggest a prevalence of 0.5 to 5% in fertile and 25 to 40% in infertile women. The most widely accepted aetiological theory is that retrograde flow of menstrual fluid through the Fallopian tubes deposits viable endometrial tissue, which implants on the peritoneal surface. Increasingly, the aetiology of endometriosis is being studied at the immunological and genetic levels. The aim of treatment of endometriosis is to remove or diminish disease deposits. This may be attempted through medical or surgical means. It has long been recognised that endometriotic glands are hormonally sensitive. Medical therapies work by inducing a hypoestrogenic, anovulatory state to induce atrophy within the glandular tissue. Conception is generally not possible during medical therapy and has not been demonstrated to increase afterwards. Medical treatment of endometriosis should be discouraged when infertility is the primary problem. In this situation surgery or an assisted reproduction treatment such as in vitro fertilisation may be more appropriate. Medical treatment of pain caused by endometriosis is generally effective. There is little difference in efficacy between the different medications but their adverse effect profiles differ greatly. It appears that gonadotropin-releasing hormone agonists, particularly when used with add-back estrogen, may be more acceptable to women than other treatments. Laparoscopic surgical treatment of minimal and mild endometriosis has been demonstrated to increase fecundity. Surgical treatment has also been shown to decrease pain scores compared with expectant management. Ongoing and future research examining the aetiology of endometriosis at the immunological and genetic levels should usher in new treatments directed at the actual cause of the disease. More randomised trials examining the role of surgery, and comparing surgical and medical treatments, are also required and are necessary if we are to continue in our attempts to adopt an evidence-based approach to treatment.