Understanding Endometriosis - the Basics

What Is Endometriosis?

Endometriosis is a common gynecological condition. It's a chronic, painful and often progressive disease in women.

Normally, the tissue that lines a woman's uterus, known as the endometrium, is found only in the uterus and is expelled from the body with each menstrual cycle. However, when a woman develops endometriosis, microscopic bits of this tissue escape from the uterus backwards into the abdomen and stick and grow on other abdominal/pelvic organs.

These endometrial cells usually implant throughout the pelvis, often involving other portions of the reproductive system, such as the ovaries, the outer wall of the uterus, the ligaments that support the uterus and the space between the uterus and the rectum. In rare cases, they can spread outside the abdomen and affect other organs, such as the lungs.

Like the endometrium itself, the transplanted tissue responds to the hormones estrogen and progesterone by thickening and may bleed every month. But because the transplanted tissue is embedded in other tissues, the blood it produces cannot escape. This causes irritation of the surrounding tissue which in turn causes cysts, scars and the fusing of body tissues. This can eventually bind the reproductive organs together so that they move as one mass when manipulated by a doctor. This can severely distort the normal anatomy of the pelvis and consequently have an extremely negative impact on fertility.

Cases of endometriosis are classified as minimal, mild, moderate or severe, depending on the size of the lesions and how deeply they reach into the other organs. They are also referred to as stage I-IV. This is considered a benign condition.

It's estimated that endometriosis affects 3-10% of women of reproductive age, and 25-35% of infertile women. In women suffering from pelvic pain the prevalence is about 40-60%. The average age at diagnosis is between 20 and 29, with similar rates within races in socioeconomic status. Symptoms usually diminish at menopause, with the marked decline in the production of estrogen.

What Causes Endometriosis?

Researchers do not know exactly why or how endometrial tissue reaches other parts of the body. One likely possibility involves a condition known as retrograde, or backward, menstruation. Normally during menstruation, portions of the sloughed-off uterine lining exit the uterus through the cervix and the vagina. But in retrograde menstruation, fragments of the endometrium flow back through the fallopian tubes and may then be carried into the abdominal cavity, giving rise to endometriosis. Doctors have found that endometriosis occurs more often in women with physical conditions that increase retrograde menstruation, such as obstructions in the vagina and cervix.

In the rare cases of endometriosis affecting the lungs or other tissue far from the uterus, researchers speculate that the stray endometrial fragments travel through the bloodstream or the lymphatic system, although no one knows just how this happens.