14 min read


Medically reviewed

All of Healthily's articles undergo medical safety checks to verify that the information is medically safe. View more details in our safety page, or read our editorial policy.

What is endometriosis?

Endometriosis is a common condition in which small pieces of tissue similar to the tissue that lines your womb (the endometrium) are found outside the womb. This could be in the fallopian tubes, ovaries, bladder, bowel, vagina or rectum.

Endometriosis affects around 2 million women in the UK. Most of them are diagnosed between the ages of 25 and 40.

Endometriosis is a long-term (chronic) condition that causes painful or heavy periods. It often causes pain in the lower abdomen (tummy), pelvis or lower back. It may also lead to lack of energy, depression and [fertility] problems.

However, the symptoms of endometriosis can vary and some women have few symptoms or no symptoms at all.

If your doctor suspects that you have endometriosis they will refer you to a gynaecologist (specialist in the female reproductive system). The gynaecologist may carry out an examination of your fallopian tubes, ovaries and womb, known as a laparoscopy, to check for patches of endometriosis.

Read more about diagnosing endometriosis.

What causes endometriosis?

The causes of endometriosis are not fully known, but there are several theories. The most common theory is that the womb lining does not leave the body properly during a period and embeds itself onto the organs of the pelvis. Doctors refer to this as retrograde menstruation.

The endometriosis cells behave in the same way as those that line the womb, so every month they grow during the menstrual cycle and bleed.

Normally, before a period, the hormone oestrogen causes the endometrium to thicken to receive a fertilised egg. If the egg isn’t fertilised, the lining breaks down and leaves the body as menstrual blood (a period).

Endometriosis tissue anywhere in the body will go through the same process of thickening and shedding, but it has no way of leaving the body. This leads to pain, swelling and sometimes damage to the fallopian tubes or ovaries, causing fertility problems.

Endometriosis treatment

There is no known cure for endometriosis. However, the symptoms can often be managed with painkillers or hormone treatments, which help prevent the condition from interfering with your daily life. Surgery can sometimes be used to improve symptoms and fertility.

A healthy diet can improve energy levels and help regulate bowel movements and sleep patterns.

Pregnancy sometimes reduces the symptoms of endometriosis, although symptoms often return once the menstrual cycle returns to normal.

Read more about how endometriosis is treated.

Endometriosis can be a difficult condition to deal with both physically and emotionally.

Endometriosis and pregnancy

One of the main complications of endometriosis is difficulty getting pregnant, or not being able to get pregnant (infertility).

Surgery can improve fertility by removing endometriosis tissue, but there is no guarantee that this will allow you to get pregnant.

Endometriosis is unlikely to put your pregnancy at risk. However, there is some evidence to show that women with endometriosis are slightly more at risk of complications during pregnancy such as pre-eclampsia, a premature birth or the need for a caesarean section.

Read information about how infertility is treated.

Endometriosis symptoms

Symptoms of endometriosis vary from person to person. Some women have no symptoms at all.

The most common symptoms include:

  • painful or heavy periods
  • pain in the lower abdomen (tummy), pelvis or lower back
  • pain during sexual intercourse
  • bleeding between periods
  • fertility problems

The experience of pain varies between women. Most women with endometriosis get pain in the area between their hips and the tops of their legs. Some women have this all the time, while others only have pain during their periods, when they have sex or when they go to the toilet.

Other symptoms may include:

  • discomfort when urinating
  • bleeding from your back passage (rectum)
  • bowel blockage (if the endometriosis tissue is in the intestines)
  • coughing blood (if the endometriosis tissue is in the lung)

How severe the symptoms are depends largely on where in your body the endometriosis is, rather than the amount of endometriosis you have. A small amount of tissue can be as painful as, or more painful than, a large amount.

Causes of endometriosis

The exact cause of endometriosis is unknown, but there are several theories about what causes it.

Retrograde menstruation

Retrograde menstruation happens when the womb lining (endometrium) flows backwards through the fallopian tubes and into the abdomen, instead of leaving the body as a period. This tissue then embeds itself onto the organs of the pelvis and grows.

It is thought that retrograde menstruation happens in most women, but many are able to clear the tissue naturally without it becoming a problem. It is possible that this is how endometriosis occurs in some women.

Retrograde menstruation is the most commonly accepted theory for endometriosis. However, it does not explain why the condition can occur in women who have had a hysterectomy.


Endometriosis is sometimes believed to be hereditary, being passed down through the genes of family members. It is rare in women of African-Caribbean origin, and is more common in Asian women than in white (Caucasian) women. This suggests that genes may play a part.

Spreading through the bloodstream or lymphatic system

Although it is not known how, endometriosis cells are believed to get into the bloodstream or lymphatic system (a network of tubes, glands and organs that is part of the body's defence against infection). This theory could explain how, in very rare cases, the cells are found in remote places such as the eyes or brain.

Immune dysfunction

It is believed that some women's immune systems are not able to fight off endometriosis effectively. Many women with endometriosis are said to have lower immunity to other conditions. However, this may be a result of the endometriosis, rather than the cause of the disease.

Environmental causes

It is thought that endometriosis may be caused by certain toxins in the environment, such as dioxins (chemical byproducts), affecting the body and its immune system.


Metaplasia is the process of one type of cell changing into another to adapt to its environment. It is this development that allows the human body to grow in the womb before birth.

It has been suggested that some adult cells retain the ability they had as an embryo to transform into endometrial cells.

Diagnosing endometriosis

If your doctor suspects that you have endometriosis, they will refer you to a gynaecologist (specialist) for a proper diagnosis. Endometriosis can only be diagnosed with an examination called a laparoscopy.


For this procedure, you will be given a general anaesthetic (put to sleep) and a special viewing tube with a light on the end (a laparoscope) will be passed into your body. The laparoscope has a tiny camera that transmits images to a video monitor so that the specialist can see the endometriosis tissue.

The specialist will then either take a small sample (a biopsy) for laboratory testing or insert other surgical instruments to treat the endometriosis.

Read more about how endometriosis is treated.

Where the laparoscope will be inserted depends on where in your body the specialist thinks the endometriosis tissue is. Because many women have symptoms around their pelvis and lower abdomen (tummy), the laparoscope is usually inserted into the pelvis through the navel (belly button).

You can usually go home the same day if you have had a laparoscopy.

Endometriosis treatment

There is no cure for endometriosis and it can be difficult to treat. The aim of treatment is to ease the symptoms so that the condition does not interfere with your daily life.

Treatment will be given to relieve pain, slow the growth of endometriosis, improve fertility and prevent the disease from coming back.

Deciding which treatment

Your gynaecologist will discuss the treatment options with you and outline the risks and benefits of each.

When deciding which treatment is right for you, there are several things to take into consideration, including:

  • your age
  • whether your main symptom is pain or difficulty getting pregnant
  • whether you want to become pregnant (some treatments may stop you getting pregnant)
  • how you feel about surgery
  • whether you have tried any of the treatments before

Treatment may not be necessary if your symptoms are mild and you have no fertility problems. In about a third of cases, endometriosis gets better by itself without treatment.

One course of action is to keep an eye on symptoms and decide to have treatment if they get worse.

Support from self-help groups can be very useful if you are learning to manage endometriosis.

Pain medication

Non-steroidal anti-inflammatories, are usually the preferred painkiller used to treat endometriosis. This is because they act against the inflammation (swelling) caused by endometriosis, as well as helping to ease pain and discomfort. It is best to take NSAIDs the day before (or several days before) you expect the period pain.

Paracetamol can be used to treat mild pain. It is not usually as effective as NSAIDs, but may be used if NSAIDs cause any side effects, such as nausea, vomiting and diarrhoea.

Codeine is a stronger painkiller that is sometimes combined with paracetamol or used alone if other painkillers are not suitable. However, constipation is a common side effect, which may aggravate the symptoms of endometriosis.

Hormone treatments

The aim of hormone treatments is to limit or stop the production of oestrogen in your body. This is because oestrogen encourages endometriosis to grow and shed. Without exposure to oestrogen, the endometriosis tissue can be reduced, which helps to ease your symptoms. However, hormone treatment has no effect on adhesions ('sticky' areas of endometriosis, which can cause organs to fuse together) and cannot improve fertility.

Read more about adhesions and other complications of endometriosis.

Hormone treatments stop the production of oestrogen by putting you in either an artificial state of pregnancy or an artificial state of menopause, which stops your periods.

Once your periods have stopped, the endometriosis is no longer aggravated. However, it is important to note that most of these treatments are not contraceptives.

There are four broad types of hormone-based treatment:

  • progestogens
  • antiprogestogens
  • the combined oral contraceptive pill
  • gonadotrophin-releasing hormone (GnRH) analogues


Progestogens are synthetic hormones that behave like the natural hormone progesterone. They stop eggs from being released (ovulation), which can help to shrink endometriosis tissue. However, they can have side effects such as bloating, mood changes, irregular bleeding and weight gain.

Drug names include [medroxyprogesterone acetate], dydrogesterone and [norethisterone].

The Mirena intrauterine system, a T-shaped contraceptive device that fits into the womb and releases progestogen, has been successfully used for the treatment of endometriosis.

Read more about the intrauterine system.


Also known as testosterone derivatives, antiprogestogens are synthetic hormones that bring on an artificial menopause by decreasing the production of oestrogen and progesterone. Side effects can include weight gain, acne, mood changes and the development of masculine features (hair growth and deepening voice).

Drug names include danazol and gestrinone. Gestrinone has fewer unpleasant side effects.

The combined oral contraceptive pill

The combined contraceptive pill contains the hormones oestrogen and progestogen. Although it is not officially licensed for the treatment of endometriosis, the pill can help relieve milder symptoms and can be taken over long periods of time. It stops the function of the ovaries, which in turn stops the menstrual cycle.

The pill can have side effects, but you can try different brands until you find one that suits you.

Gonadotrophin-releasing hormone (GnRH) analogues

Like antiprogestogens, GnRH analogues are synthetic hormones that cause an artificial menopause. They are taken as a nasal spray, implant or injection and work in a similar way to gonadotrophin-releasing hormone (a natural female hormone).

When you take GnRH analogues continuously for more than two weeks the production of oestrogen is stopped. They often have side effects such as hot flushes, vaginal dryness and low libido, so they are recommended alongside hormone replacement therapy (HRT), which is usually used to reduce the symptoms of menopause.

Drug names include [buserelin], [goserelin].


Surgery can be used to remove or destroy areas of endometriosis tissue, which can help improve symptoms and fertility. The kind of surgery you have will depend on where the tissue is. The options are:

Any surgical procedure carries risks. Discuss them with your surgeon.

Laparoscopic surgery

During a laparoscopy (a surgical procedure to gain access to the inside of your pelvis), endometriosis tissue can be destroyed or cut out using delicate instruments that are inserted into the body. This is also known as keyhole surgery.

Laparoscopy is now commonly used to diagnose and treat endometriosis. All grades of endometriosis can be successfully treated with this minimally invasive technique (where only small cuts are needed to insert the instruments). Heat, a laser or an electric current may be applied to destroy the patches of tissue.

Ovarian cysts or endometriomas, which are formed as a result of endometriosis, can also be easily treated using this technique, which can be used alongside medication such as GnRH analogues.

Although this kind of surgery can relieve your symptoms, they can sometimes recur, especially if some endometriosis tissue is left behind at the time of surgery.


This is major surgery that is used if your endometriosis is severe and extensive. Recovery time is longer than that for keyhole surgery. The surgeon makes a wide cut along the bikini line and opens up the area to access the affected organs and remove the endometriosis tissue.


If keyhole surgery and other treatments have not worked and you have decided not to have any more children, a hysterectomy (removal of the womb) can be an option. However, this is rarely required.

A hysterectomy is a major operation that will have a significant impact on your body. Deciding to have a hysterectomy is a big decision, which you should discuss with your doctor or gynaecologist. Hysterectomies cannot be reversed and there is no guarantee that the endometriosis will not return after the operation.

If the ovaries are left in place, the endometriosis is more likely to return.

The benefits of a healthy diet

Women with endometriosis may also benefit from eating a healthy, balanced diet. The benefits of this may include:

  • increasing ability to tolerate medical treatments
  • increasing ability to deal with potential side effects of treatment
  • increasing energy levels
  • helping to regulate bowel movements
  • helping to regulate sleep patterns

Your doctor may be able to refer you to a dietitian who can help you to put together a suitable diet plan.

Endometriosis complications

The main complication of endometriosis is difficulty getting pregnant (subfertility) or not being able to get pregnant at all (infertility). In some cases there may also be adhesions or ovarian cysts.

Fertility problems

The longer someone has endometriosis, the greater the chance that their [fertility] will be affected.

However, it is estimated that up to 70% of women with mild to moderate endometriosis will still be able to get pregnant without treatment. Pregnancy is also known to reduce the symptoms of endometriosis, although the symptoms often return once the menstrual cycle returns to normal.

Surgery can improve fertility by removing endometriosis tissue, but there is no guarantee that this will allow you to get pregnant.

Read information about how infertility is treated.

Adhesions and ovarian cysts

Other problems include the formation of adhesions, which are 'sticky' areas of endometriosis tissue that can fuse organs together, and ovarian cysts (fluid-filled cysts in the ovaries), which can occur when the endometriosis tissue is in or near the ovaries. In some cases, ovarian cysts (endometriomas) can become very large and painful.

Both of these complications can be removed through surgery, but may recur if the endometriosis returns.

Read information about how ovarian cysts are treated.

Content supplied byNHS Logonhs.uk
Was this article helpful?

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.