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A middle aged woman in a checked (pink and white) shirt, is clutching her stomach, as though in pain. The word – Endometriosis – can be seen

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Endometriosis is a fairly common and often painful condition in women in which endometrial-like tissue is present outside of the uterus.

The endometrium is the mucous membrane that lines the uterus. This membrane thickens during the menstrual cycle in preparation for possible implantation of an embryo and subsequent pregnancy. The problem that occurs with endometriosis is that tissue similar to the endometrium accumulates outside of the uterus and behaves like normal endometrial tissue – it builds up and breaks down with the menstrual cycle, but it cannot be shed like normal endometrial tissue during menstruation. It can appear in, or on the ovaries, the fallopian tubes, structures near the uterus, and the lining of the pelvic cavity.

Sometimes, endometrial tissue is also found in other locations including the cervix, vagina, rectum, bladder, bowel, and elsewhere. This tissue build-up can cause irritation and inflammation.

The accumulated tissue can also scar and block the fallopian tubes, thus causing infertility by preventing eggs from leaving the ovaries, or coming into contact with sperm.

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While some women with endometriosis experience pain and sometimes infertility, other affected women have no symptoms at all.

Endometriosis is experienced primarily by women during their reproductive years, although it has been reported in girls as young as 11 years of age. It is rarely seen in women who are postmenopausal. Symptoms usually go away after a woman reaches menopause. Studies further suggest that endometriosis is most common in taller, thin women with a low body mass index (BMI).

The following list describes some of the major risk factors for endometriosis in approximate order of how frequently they are associated with occurrence of the condition:

  • Family history of endometriosis
  • Early age of menarche (first occurrence of menstruation)
  • Short menstrual cycles (shorter than 27 days), but long duration of menstrual flow (more than 7 days) and heavy bleeding during menses
  • Delaying pregnancy until an older age
  • Never giving birth
  • Defects in the uterus, or fallopian tubes.

In addition to the above risk factors, there is also a report in the peer-reviewed scientific literature that red hair, blue, or green eyes, and freckles increase the odds of diagnosis of endometriosis (Peterson et al., 2010).

The large array of risk factors reported for endometriosis may be a result of varying methods used to study different populations of women, the definitions used for risk factors, and the accuracy of diagnosing the condition.

Risk factors are different than causes. The term “risk factor” is used to indicate a factor that is associated with a given outcome. However, a risk factor is not necessarily a cause. For example, beginning menstruation at an early age is a risk factor for endometriosis, meaning that a significant number of women with endometriosis began menstruation at a young age, but early onset of menstruation is not a cause of endometriosis. The cause(s) of endometriosis are not fully understood, but several theories have been suggested, including:

  • Genetics – the condition tends to run in families and affects people of certain ethnic groups more than others. In a recently published meta-analysis, Asian women were significantly more likely to have this diagnosis compared with white women, and black women were less likely to receive this diagnosis than white women (Bougie et al., 2019)
  • Retrograde menstruation – when some of the uterine lining flows up through the fallopian tubes and embeds itself on the organs of the pelvis, rather than leaving the body during menstruation
  • Dysfunction of the immune system
  • Hormones – high levels of estrogen appear to promote endometriosis
  • Surgery
  • Endometrium cells spreading through the body in the bloodstream, or lymphatic system.

None of these theories fully explain why endometriosis happens and it is likely that it is caused by a combination of factors.

The exact prevalence of endometriosis is not precisely known, but estimates range from between 2% and 10% of the general female population, and up to 50% in infertile women. It typically takes an average of 7 years for most women to be definitively diagnosed with endometriosis after the first onset of symptoms.

The long road to diagnosis often starts with the woman believing they are simply experiencing worse-than-usual monthly cramps (period pain). This condition is also often initially confused with, or misdiagnosed as, irritable bowel syndrome (IBS), a similarly painful, but very different condition requiring very different treatment.

Many women also report not being believed about the pain and other symptoms, sometimes even by their doctors. So, in addition to the physical pain of the condition, many women suffer from embarrassment, distress, and guilt, believing they should simply be strong enough to endure the symptoms. A definitive diagnosis based on laparoscopy (discussed further below) is the first step toward both relief at learning the source of this very real pain, and at getting treatment to alleviate that pain.

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Endometriosis is grouped by stage and type and considers factors, such as the location, depth, size, and amount of tissue. Different kinds of endometriosis produce different symptoms and require different kinds of treatment.

Stages of Endometriosis

The most widely used scale to measure endometriosis was developed by the American Society of Reproductive Medicine. Doctors visualize the patient’s internal affected area and assign points according to the spread of the endometrial tissue, its depth, and the areas of the body that are affected.

To observe the area, they insert a thin tube equipped with a camera and light through a small incision in the abdomen (called a laparotomy). If they observe signs of endometriosis, like implanted endometrial tissue, or scar tissue, they can simultaneously diagnose the condition and remove cysts and scar tissue. Being able to see endometriosis implants and scarring is what enables doctors to classify the disease into four different stages.

Stage 1, or minimal – there are a few small implants, or small wounds, or lesions. They may be found on organs, or the tissue lining the pelvis, or abdomen. There is little to no scar tissue.

Stage 2, or mild – there are more implants than in stage 1. They are also deeper in the tissue, and there may be some scar tissue.

Stage 3, or moderate – there are many deep implants. There may also be small cysts on one, or both ovaries, and thick bands of scar tissue called adhesions.

Stage 4, or severe – this is the most widespread. There may be many deep implants and thick adhesions. There are also large cysts on one, or both ovaries.

Researchers do not know why some people have more severe cases than others. Endometriosis does not always proceed from one stage to the next. If left untreated, it can remain the same over time, or it may get worse, or improve. In addition, the stage of the endometriosis does not necessarily reflect the level of pain experienced, risk of infertility, or symptoms present. For example, it is possible for a woman in stage 1 to be in severe pain, while a woman in stage 4 may have no symptoms present.

Endometriosis is also classified by the area of the pelvis, or abdomen, it affects. There are four main types:

  • Superficial peritoneal endometriosis. The peritoneum is a thin membrane that lines the abdomen and pelvis. It also covers most of the organs in this area. In this type, the endometrial tissue attaches to the peritoneum. This is the least severe form.
  • Endometriomas. These are dark, fluid-filled cysts, also called chocolate cysts. They vary in size and can appear in different parts of the pelvis, or abdomen, most commonly in the ovaries.
  • Deeply infiltrating endometriosis (DIE). Here, the endometrial tissue has invaded the organs either within, or outside, the pelvic cavity. This can include ovaries, rectum, bladder and bowels. In rare cases, scar tissue can bond organs so they become stuck in place. This condition is called frozen pelvis.
  • Abdominal wall endometriosis. In this type, endometrial tissue grows on the abdominal wall. The cells may also attach to a surgical incision, such as from a C-section.

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Symptoms can vary greatly and some women with endometriosis may experience no symptoms at all. The main symptom is pain in the pelvis, usually during menstruation. Some affected women might also feel pain during sex, bowel movements, and urination. Other symptoms include heavy periods, fatigue, diarrhoea, constipation, bloating, nausea, a painful caesarean section scar, or cyclical lump, and back, leg, or chest pain.

Rare symptoms of endometriosis include chest pain, or coughing blood due to endometriosis in the lungs. Headache and/or seizures can also rarely occur due to endometriosis in the brain. Transfer of endometrial cells via the bloodstream, or lymphatic system, is the most likely explanation for the cases where endometriosis is found in the brain, or other organs remote from the pelvis.

Most often, the stage and type of this condition does not affect symptoms. For example, a person with stage 1 endometriosis may have worse pain than someone with stage 4. The exception is infertility. Women at stages 3, or 4, are more likely to have trouble becoming pregnant than those at stages 1, or 2.

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Suspected endometriosis can be managed by a primary care physician, but if the cause of the pain is uncertain, or if the woman is experiencing fertility issues, she should be referred to a gynaecologist, or a specialist endometriosis centre. At a minimum, the patient should be given an abdominal examination and, if appropriate, a pelvic examination and should be informed that endometriosis is being considered.

Women with cases of severe endometriosis (or severe suspected endometriosis) involving deep tissues, such as the bowel, bladder, or ureter, should be referred to a specialist endometriosis centre accredited by the British Society for Gynaecology Endoscopy (BSGE).

At these centres, women can access specialist gynaecologists who work in conjunction with general surgeons and urologists. These specialist centres also collaborate with pain-management teams and local fertility teams.

Neither the symptoms, various types of imaging, nor physical examinations, can conclusively establish a diagnosis of endometriosis. For an accurate and definitive diagnosis, direct visual inspection inside of the abdomen, as well as biopsy of any implants, are necessary. For this visualization procedure, termed laparoscopy, the patient first undergoes general anesthesia and will therefore be asleep. The surgeon then makes a small incision in the patient’s abdomen and inserts a tiny, thin viewing tube equipped with a light (a laparoscope) to look for signs of endometriosis. The doctor may also remove a small tissue sample, or biopsy, for testing. Examination and testing of the biopsy will also help rule out other causes.

The doctor can only see superficial (not deep) peritoneal endometriosis by laparoscopy. However, before ordering further surgery, the doctor will also perform other tests, such as a pelvic exam to feel for a cyst, or an ultrasound, or magnetic resonance imaging (MRI) to look for an endometrioma, which is endometrial tissue in, or on, the ovaries. This is the most common type of endometriosis.


Endometriosis is most commonly treated by obstetrician-gynaecologists (OB-GYNs). It can be treated with medications, hormones, or surgery. The goals of treatment may include symptom relief and/or improvement of fertility.

Specific treatment for endometriosis will be determined by a health care provider based on the following considerations:

  • Overall health and medical history
  • Current symptoms
  • Extent of disease
  • The patient’s tolerance for specific medications, procedures, or therapies
  • Expectations for the course of the disease
  • The patient’s opinion, or preference
  • Desire for pregnancy.

If symptoms are mild, primary health care providers generally agree that pain medication alone is sufficient. Examples of pain relievers used to treat mild endometriosis include nonsteroidal anti-inflammatory drugs, such as ibuprofen, aspirin, naproxen, or other over-the-counter analgesics.

Hormone therapy is another effective way to treat the symptoms of endometriosis. Hormones can be administered in the form of a pill, a shot, injection, an intrauterine device (IUD), or a nasal spray. Oral contraceptives with combined oestrogen and progestin (a synthetic form of progesterone) hormones can be taken to prevent ovulation and reduce menstrual flow. If the woman cannot have oestrogen (e.g., because of cardiovascular disease, or a high risk of blood clots), then a progesterone-only pill (e.g., cerazette) could be used, but it is important to keep in mind that not all women will experience amenorrhoea, so pain may persist.

Gonadotropin-releasing hormone (GnRH) agonists are modified versions of a naturally occurring hormone which helps to control the menstrual cycle. These hormones interfere with production of oestrogen, causing endometrial implants to become inactive and degenerate. This produces a sort of “medical menopause” and symptom relief.

Danazol (also called Danocrine®) is a synthetic derivative of testosterone (a male hormone) used to treat endometriosis. It blocks the release of hormones involved in the menstrual cycle. While on this drug, women will have a period only occasionally, or not at all. The side effects of Danazol are more severe than experienced with other hormone treatments and this drug can harm a developing fetus. Therefore, it is important to prevent pregnancy while on this medication.

With all of these hormonal treatments, endometriosis symptoms return after the woman stops taking them. These medications also have side effects, including hot flashes, tiredness, problems sleeping, headache, depression, joint and muscle stiffness, bone loss, and vaginal dryness.

If medication-based treatments do not provide sufficient relief, then surgery may be necessary to remove the implants. Surgery is the preferred treatment when there is anatomic distortion of the pelvic organs, or obstruction of the bowel, or urinary tract. The surgery may be classified as either conservative, in which the uterus and ovarian tissue are preserved, or definitive, which involves hysterectomy (removal of the uterus), with, or without, removal of the ovaries. Conservative surgery is typically performed laparoscopically and endometrial implants may be removed, or destroyed, using a laser, or electrical current. If the disease is widespread, or the patient’s anatomy is distorted, laparotomy (abdominal surgery) may be required.

Some women also benefit from alternative treatments used in conjunction with other medical and surgical therapies for the treatment of endometriosis. These include:

  • Traditional Chinese medicine
  • Nutritional approaches
  • Homeopathy
  • Allergy management
  • Immune therapy.

It is important for the patient to discuss any, or all, of these treatments thoroughly with their health care provider, as some may conflict with the effectiveness of others. The National Institute for Care and Health Excellence (NICE) guidelines state that the available evidence does not support the use of traditional Chinese medicine, or other Chinese herbal medicines, or supplements for treating endometriosis.

While surgical treatments can be very effective for reducing pain, the recurrence rate of endometriosis following conservative surgical treatment can be as high as 40%. Many doctors recommend ongoing medical therapy following surgery to attempt to prevent recurrence of symptomatic disease.

Getting Pregnant

Most women who have endometriosis can conceive normally. A woman with endometriosis has several treatment options depending on the severity of the disease. In some women, surgery significantly improves their chances of getting pregnant. However, pregnancy rates tend to be lower for women with severe endometriosis.

Because some women with endometriosis have problems with ovulation, fertility drugs such as Clomid may be used to induce ovulation. Injectable hormones also may be prescribed for the same reason. Once successful ovulation is established, the doctor may suggest artificial insemination in which sperm is inserted directly into the uterus.

As mentioned above, it is critical that the doctor knows if the patient wishes to get pregnant, especially if she is receiving treatment that can either prevent pregnancy or, in the case of the hormone Danocrine, cause serious birth defects.

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In addition to the support provided by a physician, many women find it helpful to get involved with a support group of other women with endometriosis. Endometriosis UK offers a wide array of information and a directory of local support groups throughout the UK. This organization also has a confidential helpline staffed by trained volunteers who have experience with endometriosis. In addition, there is a free online community that provides a forum for women to connect with others.

The British Society for Gynaecology Endoscopy (BSGE) (