What is endometriosis?

T1-weighted magnetic resonance image of an endometrioma. Note the characteristic high signal intensity (similar to that of fat) of this right-sided adnexal endometrioma (arrow).

The uterus is lined with a layer of tissue called the endometrium. Endometrial tissue normally grows only inside the uterus (womb), but sometimes it grows outside the uterus - commonly in the reproductive organs (ovaries, fallopian tubes) or on the intestines, rectum or bladder. This condition is called endometriosis.

During menstruation the uterine lining is expelled through the vagina, but blood from endometrial tissue growing outside the uterus has no place to go. As a result, monthly bleeding in this tissue leads to the growth of cysts, lesions and scar tissue and causes the surrounding area to thicken.

Some women have little or no discomfort from endometriosis but others experience great pain before and/or during their menstrual cycle. The symptoms of endometriosis usually subside after the menopause.

How does it occur?

The causes of endometriosis are still not known and there is no simple cure. Estimates of how common it is range from 1 to 15 per cent of women of reproductive age. No single theory explains why some women develop the condition.

Some experts suggest that during menstruation, endometrial tissue "backs up" through the fallopian tubes and then settles, and grows, in the abdomen.

However, others believe that all women experience menstrual tissue back-up. In most cases, the immune system automatically destroys abnormal tissue before it attaches in the abdomen. But if the immune system is unable to get rid of the misplaced tissue, endometriosis develops.

Another theory is that remnants of a woman's own embryonic tissue, which formed while she was in her mother's womb, may develop into endometriosis during adulthood or may transform into reproductive tissue under certain circumstances.

What are the symptoms?

Some women have no symptoms. Others may experience one or more warning signs that can range from mild to severe. The type and severity of the symptoms can depend on where the endometriosis has implanted, how deeply, and how long a woman has had it; over time the extent of the adhesions build up and can cause more problems.

Common symptoms include:

• chronic pelvic pain

• very painful periods

• deep pain during sexual intercourse

• difficulty becoming pregnant

• pain during ovulation

• heavy or abnormal menstrual flow, such as premenstrual spotting/staining

• painful bowel movements, diarrhoea, constipation or other intestinal upsets during menstruation

• painful or frequent urination during menstruation

• exhaustion.

How is it diagnosed?

A doctor can evaluate your symptoms by discussing your medical history and performing a pelvic examination to check for cysts, unusual tenderness or a thickening of the pelvic area. This is best done when you are menstruating. An ultrasound scan may also be used to evaluate the pelvis.

However, you'll need a minor, day-case key-hole surgical procedure called a laparoscopy to get a firm diagnosis of endometriosis. Laparoscopy can be carried out at any time during your menstrual cycle.

Under a general anaesthetic, a surgeon will insert a small tube with a light in it (a laparoscope) into a small cut near your navel. The surgeon fills your abdomen with carbon dioxide gas to make the organs easier to see and then checks the size, location and number of endometrial growths.

Sometimes it's necessary to remove a piece of tissue (a biopsy) to reach a diagnosis. Often it is possible for the surgeon to carry out treatment at the same time as diagnosis, unless moderate or severe disease is found.
Because treatment for endometriosis-associated infertility cannot begin without a definite diagnosis, you must have a laparoscopy to confirm the condition.