Complications
Physical Health
Complications of endometriosis include internal scarring, adhesions, pelvic cysts,  chocolate cysts of ovaries, ruptured cysts, and bowel and ureter obstruction resulting from pelvic adhesions. Endometriosis-associated infertility can be related to scar formation and anatomical distortions due to the endometriosis.Ovarian endometriosis may complicate pregnancy by decidualization, abscess and/or rupture.Thoracic endometriosis can be associated with recurrent thoracic endometriosis syndrome at times of a menstrual period that includes catamenial pneumothorax in 73% of women, catamenial hemothorax in 14%, catamenial hemoptysis in 7%, and pulmonary nodules in 6%.A 20-year study of 12,000 women with endometriosis found that individuals under 40 who are diagnosed with endometriosis are 3 times more likely to have heart problems than their healthy peers.Endometriosis may increase about 1% or less chance of getting ovarian, breast and thyroid cancers in women compared with those without.It results in few deaths with unadjusted and age-standardized death rates of 0.1 and 0.0 per 100,000.Sciatic endometriosis also called catamenial or cyclical sciatica is a sciatica whose cause is endometriosis and whose incidence is unknown. Diagnosis is usually made by an MRI or CT-myelography. Mental Health
"Endometriosis is associated with an elevated risk of developing depression and anxiety disorders". Studies suggest this is partially due to the pelvic pain experienced by endometriosis patients.
Other theories
Stem cells: Endometriosis may arise from stem cells from bone marrow and potentially other sources. In particular, this theory explains endometriosis found in areas remote from the pelvis such as the brain or lungs. Stem cells may be from local cells such as the peritoneum (see coelomic metaplasia below) or cells disseminated in the blood stream (see vascular dissemination below) such as those from the bone marrow. Vascular dissemination: Vascular dissemination is a 1927 theory that has been revived with new studies of bone-marrow stem cells involved in pathogenesis. Environment: Environmental toxins (e.g., dioxin, nickel) may cause endometriosis. Toxins such as dioxins and dioxin-like compounds tend to bioaccumulate within the human body. Further research is needed but "it is plausible that inflammatory-like processes, caused by dioxin-like environmental chemicals, can alter normal endometrial and immune cell physiology allowing persistence and development of endometrial tissue within the peritoneal cavity, normally cleared by immune system cells". Müllerianosis: A theory supported by foetal autopsy is that cells with the potential to become endometrial, which are laid down in tracts during embryonic development called the female reproductive (Müllerian) tract as it migrates downward at 8–10 weeks of embryonic life, could become dislocated from the migrating uterus and act like seeds or stem cells. Coelomic metaplasia: Coelomic cells which are the common ancestor of endometrial and peritoneal cells may undergo metaplasia (transformation) from one type of cell to the other, perhaps triggered by inflammation.