Many women experience painful periods. In a minority of cases, this can be caused by endometriosis, a condition in which small pieces of the womb lining (the endometrium) grow outside the womb. Endometriosis occurs in between 1-15% of women of childbearing age. In many women it causes no symptoms, but in others it can cause severe pain and may reduce the chances of becoming pregnant.
This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.
During the menstrual cycle the lining of the womb, known as the endometrium, gradually thickens and fills with blood as it prepares for the arrival of a fertilised egg. If the egg is not fertilised, the womb lining breaks down and is lost as the monthly period. Sometimes small pieces of endometrium grow on organs outside the uterus. This is called endometriosis. The endometriosis goes through the same monthly changes as the womb lining; sometimes swelling and bleeding into the body cavity, which can cause inflammation and pain. Rubbery bands of scar tissue, called adhesions, may form. These can tie organs and tissues together and affect the normal working of organs.
Endometriosis most commonly occurs on the ovaries, on the tubes that carry eggs from the ovaries to the womb (Fallopian tubes), and on the tissues that hold the womb in place. When it occurs on the ovaries the endometriosis can forms cysts (endometrioma). These are also called chocolate cysts because of the brown fluid they contain. They may not cause any pain and may only be found during an internal examination to check fertility. However if they burst, their contents spill into the body cavity where they can cause severe pain and result in adhesions. Less commonly endometriosis can occur on the bladder or bowel or on other organs.
No one knows for certain what causes endometriosis or why some women get endometriosis and others do not. Some people believe it is caused by some menstrual fluid flowing backwards up the Fallopian tubes towards the ovaries, instead of flowing out of the body through the vagina.
Which women get endometriosis?
Endometriosis can occur in any woman of childbearing age. Endometriosis can run in families. It is more common in white people than in other ethnic groups, in women who give birth for the first time after the age of 30, and in infertile women.
Treatments for endometriosis aim to:
- relieve pain
- shrink endometriosis or slow its growth
- remove the endometriosis
- keep or bring back fertility
The type of treatment will depend on the woman's age, the severity of her symptoms, whether she wants to have children, and the severity of the endometriosis. Without treatment, endometriosis stays the same or gets better in most women, but in about one in three women it gets worse. It is important to discuss the condition with a doctor and agree a plan. If the endometriosis is mild, then drug treatment may be effective. In more severe endometriosis, surgery may be required. Sometimes it is necessary to remove the womb or one or both ovaries.
Analgesics (such as paracetamol, anti-inflammatories and codeine may help to control the pain if the symptoms are mild. Complementary medicines (such as acupuncture, aromatherapy, herbal remedies, homeopathy etc) may also help.
Hormonal treatment to shrink the endometriosis
Just like the normal endometrium, endometrial cells need the hormone oestrogen to survive and grow. Hormonal medicines that reduce the amount of oestrogen in the body will reduce the size of the endometriosis. There are several hormonal medicines that can be used:
- combined oral contraceptives (the pill)
- gonadotropin-releasing hormone (GnRH) analogues
All of these hormonal medicines work equally well overall but have different side effects. The doctor may suggest trying several medicines to find one that works and causes fewest side effects.
A barrier method of contraception (such as condoms) should be used while taking hormonal medicines (except oral contraceptives) because they can damage a developing baby.
Treatment with medicines wont cure endometriosis and symptoms usually return when the medicine is stopped. Pain returns in about 2 in 5 women 12 months after stopping treatment, and in about half after 5 years.
The aim of surgery is to remove as much of the endometriosis as possible while keeping the woman's ability to have children. Surgery is recommended:
- if the pieces of endometriosis are larger than 4 - 5cm (1.5 - 2 inches)
- if there are many adhesions or they are interfering with the normal workings of internal organs such as the bowel
- if the endometriosis is blocking the Fallopian tubes and causing infertility
- if there is severe pain which cannot be controlled with analgesics or hormones. The endometriosis may be cut away, or destroyed with heat produced by an electrical device or by using a laser. This can often be done through small cuts in the belly, using a laparoscope (keyhole surgery), but may require an open operation.
Endometriosis returns in about 1 in 5 women five years after having surgery. Hormonal medicines are sometimes given after surgery to try to delay this return. However, the only sure way to prevent endometriosis returning is to remove the ovaries. This is only considered for women with severe symptoms as a last option, or in women who are not planning to have a baby.
Tests that may be done
Ultrasound, X-ray and MRI (magnetic resonance imaging) may be used to see how the endometriosis is responding to treatment.
The National Endometriosis Society (UK)
Website written by a patient:
Website written by a doctor:
National Womens Health Information Center (US)
Endometriosis Research Center
The Endometrosis Association (Victoria)
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