Endometriosis is when the tissue that makes up the uterine lining (the lining of the womb) is present on other organs inside your body. Endometriosis is usually found in the lower abdomen, or pelvis, but can appear anywhere in the body.
With endometriosis, displaced endometrial tissue continues to act as it normally would — it thickens, breaks down and bleeds with each menstrual cycle. Because this displaced tissue has no way to exit your body, it becomes trapped. When endometriosis involves the ovaries, cysts called endometriosis may form. Surrounding tissue can become irritated, eventually developing scar tissue and adhesions — abnormal bands of fibrous tissue that can cause pelvic tissues and organs to stick to each other.
The primary symptom of endometriosis is pelvic pain, often associated with menstrual periods. Those with endometriosis typically describe menstrual pain that's far worse than usual. Common signs and symptoms of endometriosis include: