What is endometriosis?

Referenced webpage for endometriosis.

The lining of the womb is called endometrium; if endometrial-type tissue is found outside the womb it is called endometriosis. Endometriosis is most commonly found in the pelvis notably on the ovaries and behind the uterus (Figure 23.2). It can involve the bowel and urinary tract. The diagnosis is confirmed by direct visualisation usually by laparoscopy. There is a very large spectrum in the severity of endometriosis: It may consist of no more than a few tiny spots or at the other extreme, there may be extensive disease with cysts filled with a chocolate-like material and scar tissue around the pelvis. The chocolate cysts are derived from blood released by the endometriosis at the time of menstruation. Endometriosis is essentially a condition occurring in the pelvis. There are rare occasions when it may occur elsewhere such as in the lung.

Staging of Endometriosis:

There have been numerous classifications to describe the severity of the condition. The American Society for Reproductive Medicine revised the classification in 1997 to take account of the latest observations. A score is obtained according to the number of sites and the size of each deposit. Assessment of the severity of endometriosis using the revised American Fertility Society classification allows a degree of comparison although a study of the laparoscopic videotapes of 20 patients with endometriosis showed considerable variation of scoring between observers and also by the same observer on re-evaluation of the same patient.

Photographs of endometriosis can be seen at:

When there is severe endometriosis, there can be little doubt that there is a disease process. The relevance of minimal and mild endometriosis is more often a matter of debate. Some suggest that endometriosis is so commonly found in association with pelvic pain that the possibility of its presence should always be considered. Others are more sceptical as to its significance. At a meeting of the European Society of Human Reproduction and Embryology in 1991, a group of experts concluded that 'Endometriosis does not exist; all women have endometriosis.'

There is no way of looking at endometriosis and deciding whether or not it is the cause of symptoms. Ultimately a trial of therapy may seem appropriate. If symptoms respond our goal has been achieved. If symptoms do not respond the assumption must be that cause and effect have been refuted and a different causation must be sought (Q4. 3). Even when symptoms respond to treatment, this does not necessarily confirm that the endometriosis has been causative; suppression of the menstrual cycle could not only affect the endometriosis but also other conditions that are cyclically related including bowel disturbance as in the irritable bowel syndrome . The failure of symptoms to respond should be recognised as evidence that the endometriosis is probably not a factor in the pain.  

How prevalent is endometriosis?

Endometriosis is a frequent finding. An incidence of 10-25 % of all women having endometriosis is commonly quoted but if the pelvis is carefully scrutinised, the incidence is probably much higher. When there is pelvic pain or infertility an incidence of more than 60% is quoted. Recent observations, however, suggest that endometriosis is present in most if not all women at some stage. Minimal endometriosis is probably a natural process and not a disease. Endometriosis is often found coincidentally in women without symptoms. 

Related Medical Abstracts - Click on the paper title.


What causes endometriosis?

Sex hormones must play a significant role in endometriosis as the condition is not found before the onset of menstruation and is rare after the menopause. Removing the ovaries usually cures endometriosis.

The origin of endometriosis remains an area of debate. No single theory explains all aspects of endometriosis so there is presumably more than one cause. The implantation theory remains the most likely explanation for the majority of occurrences. During a period, although most of the blood is passed out through the vagina, some passes in a retrograde fashion up through the Fallopian tubes and into the peritoneal cavity (Figure 23.2). Some of this blood will contain live endometrial cells, which can implant on to structures around the pelvis. This would explain why the most common sites of endometriosis are the ovaries and the pouch behind the uterus where the fluid will collect as a result of gravity. As a result of effective contraception and reduction of breast feeding, women today experience a ten-fold increase in the number of periods they experience compared to their great-grandmothers. This may explain the increased incidence of endometriosis.

Other theories include:- Coelomic metaplasia and changes in the immune system. "metaplasia" refers to the transformation of one kind of tissue into another. Coelomic metaplasia refers to cells that transform into endometrial cells, perhaps as a result of chronic inflammation or irritation from retrograde menstrual blood. There may be a genetic predisposition.

The transplantation theory - That Endometriosis spreads via the circulatory and lymphatic system.

Latrogenic transplantation - Endometriosis is accidentally transported during surgery. Endometriosis occasionally occurs in wounds following caesarean section or hysterectomy

Coelomic metaplasia - This theory holds that certain cells, when stimulated, can transform themselves into a different kind of cells.

The hereditary theory - Women with family members who have Endometriosis are more likely, or are susceptible to developing the disease. Studies of twins have shown that there is a genetic predisposition to endometriosis. At one time it was thought that Caucasian women were more susceptible than others but the latest data shows that the only group with a genuine increased incidence is the Japanese. African women seem to be at lower risk.

Auto-immune disorder - Of all the theories being postulated for the cause of Endometriosis, the idea that this disease is an autoimmune disease seems the very likely, credible and feasible. Autoimmune diseases are now widely believed to occur based on genetic predisposition that may be triggered by environmental and other external factors.

Thin women seem to be more at risk. Endometriosis is more common in those who have not been pregnant.

If deposition of live endometrial cells in the peritoneal cavity is a common, monthly occurrence, why do the majority of women have just a few tiny spots of endometriosis at most, whilst others have severe disease? It is likely that there are a variety of mechanisms which can facilitate the development of endometriosis and others that remove endometriotic deposits. The effectiveness of these mechanisms must vary between individuals. It would seem that there is a normal dynamic process so that small endometriotic deposits develop and are then removed by natural processes. The tiny spots of endometriosis so frequently seen at laparoscopy may be a normal event that nature will usually remove without intervention. Some experts now question whether minimal endometriosis is a disease or just a normal biological process.

How can endometriosis be treated?

Medical treatment takes account of the dependence of endometriosis on sex hormones by reducing oestrogen levels or by creating a largely progestogenic or androgenic (Q 2.9) environment. It is not yet clear whether treatments designed to reduce menstrual flow exert their benefit by reducing the activity of the endometriotic deposits or by suppressing retrograde menstruation and hence deposition of endometrial cells.

  • Reducing menstrual flow by the combined oral contraceptive pill0804 or with the LNG-IUS (Mirena) for example may be beneficial.
  • Progestogens (Q33.10) or danazol (Q33.13) can be prescribed daily for several months to suppress the menstrual cycle.
  • The LNG-IUS (Mirena) is effective in the treatment of chronic pelvic pain (CPP) associated endometriosis, although no differences were observed between it and GnRH. Among the additional advantages of the LNG-IUS is the fact that it does not provoke hypoestrogenism and that it requires only one medical intervention for its introduction every 5 years. This device could therefore become the treatment of choice for CPP-associated endometriosis in women who do not wish to conceive.Insertion of an Lng-IUD after laparoscopic surgery for symptomatic endometriosis significantly reduced the medium-term risk of recurrence of moderate or severe dysmenorrhea.
    • Intrauterine progestogen (Mirena-LNG-IUS) is effective in symptom control throughout the 5 years on the device, and discontinuation is greatest between 3 and 6 months. For those patients with improvement in symptoms, it is an acceptable long-term alternative. TheMirena is effective in symptom control throughout the 3 years on the device, and discontinuation is greatest between 3 and 6 months. For those patients with improvement in symptoms, it is an acceptable long-term alternative. The levonorgestrel intrauterine system is an effective hormonal option for treating symptomatic endometriosis (minimal to moderate). It also alters the American Fertility Society staging of disease. With a continuation rate of 68% after 6 months, it has the potential for providing long-term therapy in a substantial number of sufferers, although this would require further study and verification. The Mirena greatly reduces pain associated with endometriosis and adenomyosis and delays disease recurrence. Irregular bleeding and spotting is the main side effects. Administration of GnRHa in advance does not improve the bleeding symptoms.
    • Endometriosis tends to disappear after the menopause. A relatively new set of drugs called gonadotrophin releasing hormone analogues (GnRH –gonadotrophins) provide a temporary menopause like state and they have proven value in the treatment of endometriosis. They should usually be used for a maximum of six months at a time as there is concern that prolonged suppression of oestrogens may have an adverse effect on the bones and arteries. In some circumstances it may be appropriate to continue GnRH analogues in combination with add-back HRT therapy (Q 27.27).
    • Exercise is associated with a reduction of oestrogen and sometimes helps.
    • It is acceptable to provide a trial of medical treatment for presumed endometriosis without performing a diagnostic laparoscopy first ( laparoscopy).
    • Some gynaecologists treat endometriosis by laser or diathermy during laparoscopy. Studies are currently underway to compare the relative merits of GnRH analogues and laser therapy. Almost invariably, removing the ovaries will cure endometriosis and this may be the operation of choice combined with hysterectomy once your family has been completed.
    • The relationship between endometriosis and pelvic pain is open to debate. It is a common observation that the severity of symptoms and the severity of the endometriosis do not correlate. Some with severe pain have just a few tiny spots of endometriosis whilst others with severe endometriosis may be symptom free. In a series of 33 patients having a second laparoscopy for persistent pelvic pain after laser therapy, more than half had no evidence of residual endometriosis. We should therefore be cautious in assuming that when endometriosis is discovered that it is necessarily the cause of pain. Failure of symptoms to respond to treatment may suggest that the endometriosis is not the cause of the pain rather than that the treatment of the endometriosis is not effective.
    • The classic, unproven dogma that ovarian endometrioma should be removed in all infertile women prior to IVF has been recently questioned. Both endometrioma-related injury and surgery-mediated damage may be claimed to be involved and the relative importance of these two insults remains to be clarified. Convincing evidence has emerged showing that responsiveness to gonadotrophins after ovarian cystectomy is reduced. Conversely, the impact of surgery on pregnancy rates is unclear since no deleterious effect has been reported. Of relevance here is that surgery exposes women to risk related to a demanding procedure whereas risks associated with expectant management are mostly anecdotal or of doubtful clinical relevance. Juan et al recommend proceeding directly to IVF to reduce time to pregnancy, to avoid potential surgical complications and to limit patient costs. Surgery should be envisaged only in presence of large cysts,or to treat concomitant pain symptoms which are refractory to medical treatments, or when malignancy cannot reliably be ruled out.

    Support Groups

    National Endometriosis Society

    50 Westminster Palace Gardens

    1 7 Artillery Row

    London SW1pRL

    Tel: 020 7222 2781

    Endometriosis Support Groups:

    Members of a support group, provide each other with various types of help and information for a particular shared difficulty.

    The support may take the form of providing relevant information,

    • relating personal experiences,
    • listening to others' experiences,
    • providing sympathetic understanding and
    • establishing social networks.

    A support group may also provide ancillary support, such as serving as a voice for the public or engaging in advocacy.

    Support groups maintain interpersonal contact among their members in a variety of ways.

    Support groups also maintain contact through printed information rich newsletters, telephone chains, internet forums, and mailing lists.

    Support groups offer companionship and information for people coping with diseases or disabilities. Support groups may not be appropriate for everyone, and some find that a support group actually adds to their stress rather than relieving it.



    Evaluation of the quality of Web sites is discussed in (Q4.27). You may find that several general women's health sites may help you (internet information). The following are more specialised relevant Web sites:-

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This is the personal website of David A Viniker MD FRCOG, retired Consultant Obstetrician and Gynaecologist - Specialist Interests - Reproductive Medicine including Infertility, PCOS, PMS, Menopause and HRT.
I do hope that you find the answers to your women's health questions in the patient information and medical advice provided.

I do hope that you find the answers to your women's health questions in the patient information and medical advice provided.


The aim of this web site is to provide a general guide and it is not intended as a substitute for a consultation with an appropriate specialist in respect of individual care and treatment.

David Viniker retired from active clinical practice in 2012. He now writes articles to support website promotion, examples can be found on dyslexia treatment with coloured tinted glasses, counselling in Woodford, top positioning on Google and website development in Essex.
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