What Is Endometriosis? – Causes, Symptoms and Treatment

By MD, PhD, MSc (gynecologist), MD, MSc (gynecologist), MD, FACOG, FACS, FACE (reproductive endocrinologist), BSc, MSc (embryologist), BSc, MSc (embryologist) and BA, MA (fertility counselor).
Last Update: 09/20/2018

Endometriosis is a condition that causes endometrial tissue to grow outside the uterine cavity. The symptoms associated with endometriosis vary depending on the severity of the condition and the place where endometrial tissue is growing. For example, it it affects the ovary (ovarian endometriosis), it will cause ovarian cysts to grow (endometriomas).

Its effects on female fertility, the complications that it might cause to achieve a pregnancy, and the chances of getting pregnant using In Vitro Fertilization (IVF) will depend on the type of endometriosis as well. In the most severe cases of endometriosis (stage IV), the woman may have no alternative but to use donor eggs to have offspring.

Definition & location

The uterus (womb) is formed by an external muscular layer named myometrium, and an internal mucous layer named endometrium, which detaches regularly and is expelled during menstruation.

Endometriosis, commonly referred to as endo, is defined as the growth of endometrial tissue outside the uterine cavity.

It is a common condition in women of childbearing age. Endometriosis causes pain, which increases during menstruation. It is estimated that endometriosis affects 10-20% of women of reproductive age in America.

Endo is a common cause of female infertility, since 30-40% of women that suffer from it have, subsequently, problems to achieve pregnancy. Different severity levels (stages) can be distinguished, depending on the location, deepness, quantity and size of the tissue.

This growth can take place in several parts of the body, such as the ovaries, the Fallopian tubes, behind the uterus, on the uterine ligaments, in the pelvic cavity, and also but rarely in other areas, such as the bladder.

Based on the location where endometrial tissue grows, we can distinguish between:

  • Ovarian endometriosis
  • Tubal endometriosis
  • Pelvic endometriosis
  • Rectal endometriosis
  • Intestinal endometriosis
  • Peritoneal endometriosis


The classification made by the American Society for Reproductive Medicine (ASRM) is the most commonly used nowadays to determine the levels of severity of endometriosis. According to the ASRM, we can distinguish for types of endo based on their degree of severity:

Stage 1 (minimal)
Isolated implants are found superficially, without adhesions.
Stage 2 (mild)
It distinguishes itself by the growth of superficial implants of 5 cm approximately. They tend to grow around the peritoneum and the ovaries. Other organs may be affected, too.
Stage 3 (moderate)
Several implants are detected, which can be superficial or invasive. They grow around the tubes and ovaries.
Stage 4 (severe)
A large number of cysts and severe adhesions appear.


The causes why this kind of growth takes place outside its common location are not completely known.

It is believed that it can be due to some fragments of the endometrium that are not expelled during menstruation. They ascend along the Fallopian tubes and get adhered to some organs of the pelvic cavity, where the tissue develops forming bulges or cysts, named endometrial implants.

Other causes may be due to genetic factors, which means this condition could be inherited, thus having certain predisposition to suffer from it.

It could also be provoked by immunological or endocrine causes, but all of them are being studied. In fact, it is most likely due to a multifactorial mechanism rather than a single one.

The physiopathology of endometriosis is still a field of continuos study, since discovering the causes of this disease could be determining to finding effective treatments to fight against it.

Some risk factors associated with endometriosis in females include:

  • Family history of endometriosis
  • Not having had children
  • Giving birth for the first time after age 30
  • Abnormalities of the genital tract
  • Uterine anomalies
  • Having menstrual period too often which last 7 or more days
  • Having had the first period very early
  • Immunological diseases, such as lupus or multiple esclerosis


As if it was a normal endometrium, the implants found in several parts of the body respond to the hormonal changes in progesterone and estrogenic hormone during the menstrual cycle. They bleed too, just like the uterine endometrium, the difference lies in the fact that this blood is not expelled outside of the body, hence provoking the inflammation of the tissues that surround them and scars in those tissues (adherences).

The most common symptom is a mild to intense pain in the abdomen, pelvis and lower back. Generally, this pain increases during the period and it’s not related to the quantity of endometriosis that a woman can have.

Other symptoms include:

  • Pain in the intestine and intestinal disorders, such as constipation or diarrhea.
  • Pain during and after sexual intercourse (dyspareunia).
  • Pain when urinating while on your period, or even hematuria or blood in urine.
  • Longer periods, in which there’s an increase in the expelled blood.
  • Brown spotting or bleeding between periods and before them.
  • Exhaustion and fatigue


In order to diagnose endometriosis, a complete physical examination with special attention to the pelvic area must be performed. The information gathered, along with the medical history, will help to reach an accurate diagnosis.

Other tests that can be carried out are an ultrasound, in which the images of the genital organs are obtained, or in some cases, a magnetic resonance imaging to obtain a picture in two dimensions of some organ.

Magnetic resonance imaging (MRI) can be used in patients with an unclear previous diagnosis via ultrasound, or in before undergoing surgery. MRI is used to determine the exact location of endometrial implants as well as the deepness of the lesions.

Even though MRI is a very useful tool to diagnose endometriosis, it is highly expensive, hence the fact that it is not so commonly used.

Nevertheless, the doctor will only be sure of the diagnosis when a laparoscopy is performed. It is a minor surgery with general anesthesia, in which through a tube equipped with a lens and a light, the inside of the abdominal cavity can be observed.

Recent researches are trying to find endometriosis biomarkers that allow a diagnosis by carrying out a simple blood or urine analysis. These markers would be substances created by our body in response to the illness or created by the illness itself.

Endometrial markers in the endometrial fluids have been discovered so far, such as the CA-125 tumor marker, which means an analysis of the endometrial fluids would allow detecting the illness. However, to date, their diagnostic value is limited.


Endometriosis can’t be cured nowadays. Its treatment consists on relieving the pain of the woman that suffers from it, so that she can carry a normal life.

Since it depends on hormones, endometriosis is present during all her fertile life, and sometimes even longer.

Depending on the severity of the symptoms, one of the following treatments may be indicated:

In cases of mild endometriosis, painkillers to relieve the symptoms may be enough. Unfortunately, this option is insufficient in many cases.
The development of endometrial tissue can be stopped by administering the hormones involved in the menstrual cycle artificially. Oral contraceptives are an example.
In the most severe cases, endometriosis can be treated surgically. Based on the location and expansion, the surgical procedure will vary.

As one shall see, the treatment depends on the stage of endometriosis. In the mildest cases, the treatment will consist on painkillers and in the most severe cases, when chronic pain is experienced, surgery can be a good option.

The patient must be informed of the advantages and disadvantages of every treatment, since some of them, such as the hormonal, may not be compatible with the idea of having children.

Can you recover fertility after treating endometriosis with surgery?

Unfortunately, surgery to treat endometriosis is indicated in certain cases only, Dr. Blanca Paraíso, OB/GYN specialized in Reproductive Medicine, states.

Examples of cases where surgery is typically indicated include women who cannot be diagnosed using the normal procedures for diagnosis, women with severe symptoms that cannot be controlled with a medical treatment, women with too large endometriomas or endometriomas that grow too fast, or those with endometriomas in other locations, such as the bladder, that can lead to serious symptoms.

According to Dr. Blanca Paraíso, in some cases, fertility increases after laparoscopy to treat endometriosis. However, on the other side of the coin, the ovarian reserve may be affected, especially if surgery involves the resection of an ovarian cyst (endometrioma), as surgery will damage the healthy tissue that surrounds the endometriomas.

As a result, the number of eggs retrieved may be less than normal, hence the fact that laparoscopy is indicated as a treatment option for women with endometriosis only in particular cases, not as an option to recover fertility even though it may improve it temporarily.

Fertility treatments and costs

In women with stage I endometriosis (mild), pregnancy can be achieved naturally or with just Intrauterine Insemination (IUI).

However, given that endometriosis affect the woman's ovarian reserve and the functionality of the tubes, the fertility treatment with the highest chance of success in these cases is In Vitro Fertilization (IVF).

The cost of conventional IVF or IVF/iCSI ranges between $8,500 and $12,000. It should be noted that the cost of medications is rarely included in the initial cost. As for the UK, the cost of IVF is usually around £5,000 per cycle of treatment.

In the most severe cases of endometriosis, egg quality may be affected as well. This is the reason why many women have no alternative but to use donor eggs to get pregnant. In the USA, IVF with donor eggs can cost up to $20,000-$40,000, while in countries like Spain, the price ranges between €4,700 and €7,600.

IVF with donor eggs is probably the most confusing of all fertility treatments, and oftentimes, a misleading one. Transparency is one of our strict selection criteria when it comes to recommending fertility clinics to our readers. You can create your Fertility Report now to filter clinics based on our selection criteria and get an individual report based on your preferences with answers to your queries and most importantly, to prevent potential frauds.

FAQs from users

What are your reproductive options if you have stage IV endometriosis?

By Mark P. Trolice MD, FACOG, FACS, FACE (reproductive endocrinologist).

Endometriosis affects 10-15% of all women. Of women with endometriosis, 30-50% are estimated to have infertility; of women with infertility, 25-50% are estimated to have severe endometriosis. A hallmark of endometriosis is inflammation and subsequent formation of adhesions in the pelvis. These adhesions distort the pelvic anatomy and impacts the woman in a variety of ways. The most direct consequence of adhesions can be a disruption of the anatomical relationship between the ovaries and fallopian tubes. In advanced cases of endometriosis, tubal blockage may occur to the point of a hydrosalpinx which may require removal before any fertility treatment.

The most appropriate treatment for each couple will depend on a number of factors including the woman’s age, the duration of infertility, her ovarian reserve, the sperm analysis, a history of past surgery for endometriosis and its severity.
For women younger 35 years of age with low stage disease, a trial of Fertility treatment with intrauterine insemination (IUI) is recommended. However, for women greater than or equal to 35 years of age with advanced stages of endometriosis (stages III and IV), IVF is recommended due to the higher pregnancy rate. Of note, advanced endometriosis, compared to other diagnoses, may reduce the pregnancy rate with in vitro fertilization.

Which is more effective with mild endometriosis, IUI or IVF?

By Manuel Aparicio Caballero MD, MSc (gynecologist).

Intrauterine Insemination (IUI) is the treatment of choice for young patients with mild-to-moderate endometriosis (stages I and II). For this treatment to be possible, no blockage in the Fallopian tubes must exist. However, recent studies suggest that IUI may be ineffective in these cases. The latest European review on the average success rates during years 2016-2017 with AIH (artificial insemination by husband) are below 15% per cycle. So, in conclusion, opting for IUI in cases of mild-to-moderate endometriosis is possible in very particular cases where there is evidence that it might work.

In general, In Vitro Fertilization (IVF) is the first option for patients with a moderate or severe type of endometriosis (stages III and IV), as well as for women with previous failed cycles in spite of having a good prognosis initially.

Can endometriosis lead to cancer?

By Zaira Salvador BSc, MSc (embryologist).

It is estimated that just 1% of the cases of endometriosis end up with a cancer diagnosis, that is, become malignant. However, more studies that confirm this prevalence are necessary.

Can Synarel (Nafarelin acetate) be used to treat endometriosis?

By Zaira Salvador BSc, MSc (embryologist).

Yes, it is a common hormonal treatment prescribed to relieve the symptoms of endometriosis. It is a nasal spray which main active ingredient is Nafarelin acetate, a GnRH agonist.

Can endometriosis cause uterine polyps?

By Rebeca Reus BSc, MSc (embryologist).

Several scientific studies have shown that the risk of endometrial polyps increases in endometriosis patients. It should be noted that both are estrogen-dependent overgrowths of the endometrium, some it is only logical that they are associated with each other in some aspects. Moreover, this rate is believed to be slightly higher in women with stage 2 and stage 3 endometriosis compared with those at stage 1.

Suggested for you

To learn more about your options to achieve pregnancy with endometriosis, we recommend that you have a look at the following article: Can You Get Pregnant with Endometriosis? – Your Chances of Success.

Our editors have made great efforts to create this content for you. By sharing this post, you are helping us to keep ourselves motivated to work even harder.


ADAEC. Endometriosis: Documento de consenso S.E.G.O. La voz digital [periódico digital] 2007.

Adamson GD, et al. Creating solutions in endometriosis: global collaboration through the World Endometriosis Research Foundation. J of Endometriosis 2010;2(1):3-6.

Allen C, Hopewell S, Prentice A. Non-steroidal anti-inflammatory drugs for pain in women with endometriosis. Cochrane Database of Systematic Reviews 2005, Issue 4.

American College of Obstetricians and Gynecologists (ACOG). Medical management of endometriosis. Washington (DC): American College of Obstetricians and Gynecologists (ACOG); 1999 Dec. 14 p. (ACOG practice bulletin; no. 11).

ASRM American Society for Reproductive Medicine. Endometriosis. Guía para pacientes. En: Serie de Información para pacientes. Revisado en 2013. Birmingham, Alabama.

Clement PB. The pathology of endometriosis: a survey of the many faces of a common disease emphasizing diagnostic pitfalls and unusual and newly appreciated aspects. Adv Anat Pathol. 2007; 14(4):241-60

Davis L, Kennedy SS, Moore J, Prentice A. Modern combined oral contraceptives for pain associated with endometriosis. Cochrane Database of Systematic Reviews: Reviews 2007, Issue 3.

Di W, Guo SW. Curr Opin Obstet Gynecol. The search for genetic variants predisposing women to endometriosis. 2007; 19(4):395-401.

Dra. MA. Martínez Zamora. (2013). Actualización sobre la etiopatogenia de la endometriosis. Hospital Clínic Universitari de Barcelona. Acadèmia de Ciències Mèdiques i de la Salut de Catalunya i de Balears, Societat Catalana d’Obstetricia i Ginecologia

European Society for Human reproduction (ESHRE). Guideline for the diagnosis and treatment of endometriosis. Human Reproduction, 2005; 20(10):2698-2704.

Giudice LC. Endometriosis. Clinical Practice. N Engl J Med 2010;362(25):2389-98.

Guo S-W, et al. Reassessing the evidence for the link between dioxin and endometriosis: from molecular biology to clinical epidemiology. Mol Hum Reprod 2009;15(10):609-24.

Hughes E, Fedorkow D, Collins J, Vandekerckhove P. Ovulation suppression for endometriosis. Cochrane Database of Systematic Reviews 2003, Issue 3.

Husby GK1, Haugen RS, Moen MH. Diagnostic delay in women with pain and endometriosis. Acta Obstet Gynecol Scand. 2003 Jul;82(7):649-53.

Moen MH and Magnus P. The familial risk of endometriosis. Acta Obstet Gynecol Scand 1993;72(7):560-4.

Nnoaham KE, et al. Impact of endometriosis on quality of life and work productivity: a multicenter study across ten countries. Fertil Steril 2011;96(2):366-373.

Rogers PA, et al. Priorities for endometriosis research: recommendations from an international consensus workshop. Reprod Sci 2009;16(4):335-46.; Adamson GD, et al. Creating solutions in endometriosis: global collaboration through the World Endometriosis Research Foundation. J of Endometriosis 2010;2(1):3-6.

Royal College of Obstetricians and Gynaecologists. The investigation and management of endometriosis. London: RCOG; 2006. Green-top Guideline No. 24.

Simoens S, Hummelshoj L, D'Hooghe T. Endometriosis: cost estimates and methodological perspective. Hum Reprod Update. 2007; 13(4):395-404.

Society of Obstetricians and Gynaecologists of Canada. Consensus guidelines for the management of chronic pelvic pain. Ottawa: SOGC; 2005. SOGC Clinical Practice Guidelines No 164.

Vigano P, et al. The relationship of endometriosis and ovarian malignancy: a review. Fertil Steril 2008;90(5):1559-70.

Vigano P, Somigliana E, Vignali M, Busacca M, Blasio AM. Genetics of endometriosis: current status and prospects. Front Biosci. 2007; 12:3247-55.

Wieser F, Cohen M, Gaeddert A, Yu J, Burks-Wicks C, Berga SL, Taylor RN. Evolution of medical treatment for endometriosis: back to the roots? Hum Reprod Update. 2007; 13(5):487-99.

FAQs from users: 'What are your reproductive options if you have stage IV endometriosis?', 'Which is more effective with mild endometriosis, IUI or IVF?', 'Can endometriosis lead to cancer?', 'Can Synarel (Nafarelin acetate) be used to treat endometriosis?' and 'Can endometriosis cause uterine polyps?'.

Read more

Authors and contributors

 Blanca Paraíso
Blanca Paraíso
MD, PhD, MSc
Bachelor's Degree in Medicine and Ph.D from the Complutense University of Madrid (UCM). Postgraduate Course in Statistics of Health Sciences. Doctor specialized in Obstetrics & Gynecology, and Assisted Procreation. More information about Blanca Paraíso
License: 454505579
 Manuel Aparicio Caballero
Manuel Aparicio Caballero
Bachelor's Degree in Medicine from the University of Murcia. Specialist in Obstetrics & Gynecology. Master's Degree in Human Reproduction from the King Juan Carlos University and the IVI. Currently, he is part of the team of Tahe Fertilidad (Murcia, Spain). More information about Manuel Aparicio Caballero
License: 303008030
 Mark P. Trolice
Mark P. Trolice
Reproductive Endocrinologist
Mark P. Trolice is the Director of Fertility CARE – The IVF Center and Clinical Associate Professor in the Department of Obstetrics & Gynecology (OB/GYN) at the University of Central Florida College of Medicine. He is Board-certified in REI and OB/GYN, and maintains annual recertification. His colleagues select him as Top Doctor in America® annually, one among the top 5% of doctors in the U.S. More information about Mark P. Trolice
License: ME 78893
 Rebeca Reus
Rebeca Reus
BSc, MSc
Degree in Human Biology (Biochemistry) from the Pompeu Fabra University (UPF). Official Master's Degree in Clinical Analysis Laboratory from the UPF and Master’s Degree about the Theoretical Basis and Laboratory Procedures in Assisted Reproduction from the University of Valencia (UV). More information about Rebeca Reus
 Zaira Salvador
Zaira Salvador
BSc, MSc
Bachelor's Degree in Biotechnology from the Technical University of Valencia (UPV). Biotechnology Degree from the National University of Ireland en Galway (NUIG) and embryologist specializing in Assisted Reproduction, with a Master's Degree in Biotechnology of Human Reproduction from the University of Valencia (UV) and the Valencian Infertility Institute (IVI) More information about Zaira Salvador
License: 3185-CV
Adapted into english by:
 Sandra Fernández
Sandra Fernández
Fertility Counselor
Bachelor of Arts in Translation and Interpreting (English, Spanish, Catalan, German) from the University of Valencia (UV) and Heriot-Watt University, Riccarton Campus (Edinburgh, UK). Postgraduate Course in Legal Translation from the University of Valencia. Specialist in Medical Translation, with several years of experience in the field of Assisted Reproduction. More information about Sandra Fernández

Find the latest news on assisted reproduction in our channels.