What is endometriosis?

Endometriosis is a condition where endometrial tissue that normally lines the uterus (and is shed during a period), is found outside the uterus.  The most common sites to find endometriosis are the ovaries, the fallopian tubes, the outer lining of the uterus, the lining of the pelvis, and the uterosacral ligaments (that support the cervix and hold it in place).  Less common sites for endometriosis include; the surface of the rectum, the small and large bowel, the bladder and the vagina.  Rarely endometriosis has been found in the umbilicus and under the diaphragm.  This ectopically located endometrial tissue responds to the same hormones as the normally sited endometrium, but as the tissue builds up and is shed, comparable to a period – there is nowhere for the blood and tissue to be flushed away, so it causes localised inflammation, pain and scarring.

How common is endometriosis?

Up to 1 in 5 women in the reproductive age group will have some evidence of endometriosis.  Severe symptomatic endometriosis occurs in up to 5% of the population.  Typically, after the menopause symptoms improve and during pregnancy symptoms are often less severe.

What are the symptoms?

Symptoms can include painful periods (medically called – dysmenorrhoea), pain – particularly in the pelvis, but also sometimes in the low back and in the abdomen, pain with intercourse, infertility, and sometimes some pre-menstrual spotting.  If the endometriosis involves the rectum or bowel, this can cause painful defaecation or even blood in the bowel motion.

How is it diagnosed?

Often there is a strong clinical suspicion, but there is no blood test, X-ray or scan that can give a definitive diagnosis.  The only sure way to make a diagnosis is to take a biopsy.  This can usually be done via laparoscopy and often treatment can be performed at the same time.


For milder endometriosis, simple analgaesics may keep things under control.  For more severe symptoms there are some medical therapies that usually involve some kind of hormonal treatment to suppress the endometriosis.  For more advanced disease, surgery is usually required.  Most of the time surgery can be done via a laparoscopic (keyhole) approach. 

Schematic images of endometriosis.

Laparoscopic photograph of endometriosis involving the lining of the pelvis called the peritoneum