• Basics

    Endometriosis is a disease that occurs when the cells of the tissue lining the uterus (the endometrium) travel to other parts of the body and begin to grow Figure 01. Areas affected by this misplaced tissue may include the ovaries, the fallopian tubes, the area behind the uterus, the area between the vagina and rectum, and the pelvis. The misplaced tissue can also grow on the colon, the wall of the abdomen, the appendix, and the lungs.

    Click to enlarge: Female reproductive anatomy

    Figure 01. Female reproductive anatomy

    Misplaced tissue, like the uterine lining, reacts to the hormones estrogen and progesterone during the menstrual cycle. Each month, the misplaced tissue builds up to prepare for implantation of an egg. However, as these tissue cells are shed, they have no way of exiting the body. This means that they can build up over time to form lesions, masses, and bands of scar tissue (called adhesions).

    Areas where misplaced tissue collects often become inflamed and swollen, are tender to the touch, and can be extremely painful.

    Endometriosis tends to be a progressive disease, which means that symptoms usually get worse over time. However, there are no adequate long-term studies of the progression of endometriosis to truly say that is it gets worse in most women.

    Endometriosis is usually confirmed and treated by a gynecologist. Your primary care doctor, however, is often the first to recognize endometriosis. A team of specialists, including an endocrinologist and a surgeon, may also become involved in your care.

  • Causes

    Experts are not exactly sure what causes endometriosis Table 01. The cause of endometriosis is not known. Many medical researchers believe that it is due to a process called “retrograde menstruation.” In this process, small amounts of blood and tissue flow backward into the fallopian tubes during menstruation. From there, they leak out and begin to grow in the pelvis and abdomen. This process occurs in almost every woman, but certain women have weaknesses in their immune systems that interfere with their bodies' ability to expel the blood and tissue fragments. Another theory suggests that uterine tissue is carried through the blood vessels or lymphatic system to distant organs, where it implants itself and grows. Studies also show that endometriosis is common in women with a family history of the disease. In addition, if a woman has a first-degree relative with endometriosis, she has a higher risk for more severe disease. Finally, a more controversial theory suggests that endometriosis is caused by exposure to environmental toxins, mainly dioxin, which is a by-product of pesticides, bleached pulp and paper products, and the burning of medical or municipal waste.

    Table 1.  Possible Causes of Endometriosis

    Cause What happens
    Backflow of blood and tissue into the fallopian tubes during menstruation (retrograde menstruation) Blood and tissue fragments may begin to grow in the pelvis and abdomen after flowing back through the fallopian tubes. Certain women are thought to be more vulnerable to this process because their bodies are unable to expel these fragments naturally.
    Distribution of uterine tissue through the blood vessels or lymphatic system Misplaced uterine tissue may travel through the blood vessels or channels of the body's lymph system to distant organs (including the abdomen, lung, and lymph nodes in the pelvis). It then attaches itself and begins to grow.
    Genes The gene for endometriosis may be inherited through the mother. Having a twin sister with the disease also increases risk
    Environmental toxins Studies in monkeys suggest that long-term exposure to the pesticide dioxin leads to endometriosis. Some studies in women with endometriosis have shown higher levels of dioxin in their bloodstream compared to women without endometriosis.

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