What is Endometriosis? Why should you care?

Definition: Endometriosis is a women’s disorder where tissue similar to the lining of the uterus is found elsewhere in the body – mainly in the abdominal cavity thus causing chronic pelvic pain, heavy bleeding and infertility. It is clinically described as a chronic illness but not a terminal illness – where life threatening complications have not set in.


The exact cause of endometriosis isn’t known, and there are several theories regarding the cause, although no one theory has been scientifically proven. However, one of the  oldest theory is that Endometriosis is caused by retrograde menstruation, in which fragments of menstrual endometrium are refluxed through the fallopian tubes into the peritoneal cavity (Sampson, 1927).

A second theory is that hormones transform the cells outside the uterus into cells similar to those lining the inside of the uterus, known as endometrial cells.

A third theory is that the endometrial cells are transported out of the uterus through the lymphatic system. Still another theory purports it may be due to a faulty immune system that isn’t destroying errant endometrial cells.

Some believe endometriosis might start in the fetal period with misplaced cell tissue that begins to respond to the hormones of puberty. This is often called Mullerian theory. The development of endometriosis might also be linked to genetics or even environmental toxins

Others believe the condition may occur if small areas of your abdomen convert into endometrial tissue. This may happen because cells in your abdomen grow from embryonic cells, which can change shape and act like endometrial cells. It’s not known why this occurs.

It’s also possible for the menstrual blood to leak into the pelvic cavity through a surgical scar, e.g C-section.

Symptoms: Classic endometriosis symptoms include; Painful, heavy, prolonged or irregular periods, pain during or after sex, infertility, painful bowel movements and fatigue.

Stages: In the most commonly used classification system, endometriosis stages are as follows: 1-minimal, 2-mild, 3-moderate, and 4-severe. These reflect the extent of disease, which occurs when tissue that is similar to the kind that lines the uterus (endometrium) grows outside of it.

Specifically, endometriosis stages reflect the number of growths (implants), their depth, and whether endometriomas (cysts) or scarring are present.

Endometriosis is a painful condition, but endometriosis stages do not necessarily reflect the level of pain or specific symptoms a person experiences.

This article discusses what the four stages of endometriosis mean, how they’re diagnosed, and the role of other classification systems.

Endometriosis Staging System

There are different ways to classify the severity of endometriosis. The most common method is a points rating and numerical scale system created by the American Society of Reproductive Medicine (ASRM).

This determines disease stages by assigning points according to characteristics of the disease. 

ASRM’s scale has four endometriosis stages:

  • Stage 1: Minimal disease (five points or less)
  • Stage 2: Mild disease (six to 15 points)
  • Stage 3: Moderate disease (16 to 40 points)
  • Stage 4: Severe disease (41 points and higher)

In addition to the current scale, researchers are also working on new methods to evaluate and stage endometriosis.

How Points Are Assigned

Unless endometriosis is advanced and has caused other issues with organs and structures, it typically doesn’t show up on diagnostic imaging tests such as a computed tomography (CT) scan or ultrasound.

The only way for a healthcare provider to confirm the diagnosis is to do endometriosis surgery to look inside the pelvis and abdomen.

If indications of endometriosis are seen, a surgeon may be able to make the diagnosis visually. Regardless, they will still take a sample of tissue (biopsy) to look at under a microscope.

Depending on the stage of the disease, lesions can vary in appearance, color, and depth. Even using surgical lighting and scopes, surgeons may not be able to see lesions that are superficial and clear, for example.

Using the ASRM staging system, points are then assigned based on the characteristics of the endometrial lesions to determine the stage of endometriosis.

Stage 1 Endometriosis

Stage 1, or “minimal” endometriosis, is used for cases that:5

Subramanian A, Agarwal N. Endometriosis – Morphology, clinical presentations and molecular pathologyJ Lab Physicians. 2010;2(1):1. doi:10.4103/0974-2727.66699

  • Involve few small and superficial endometrial growths
  • Have growths on organs or the tissue that lines the pelvis and abdominal cavity
  • Show minimal or no scar tissue

Having stage 1 endometriosis doesn’t mean a person will have few or no symptoms, or that the disease won’t have a major impact on their life.

Stage 2 Endometriosis

Stage 2 endometriosis defines “mild disease.” At this stage, there is evidence of:

  • More implants than in stage 1
  • Deeper implants than in stage 1
  • Possible scar tissue, but no signs of active inflammation

Endometriosis implants can be located throughout the body, but tend to be found on or near the ovaries, fallopian tubes, and area behind the uterus.

Stage 3 Endometriosis

Stage 3 endometriosis is for “moderate” disease. At this stage, there are:

  • Many deep endometrial implants
  • Cysts (ovarian endometriomas) in at least one of the ovaries
  • Filmy adhesions (in some cases)

Ovarian endometriomas form when endometrial tissue attaches to an ovary. As the tissue sheds, it collects along with old, thick, brown blood.

Based on the appearance of the blood, ovarian endometriomas are sometimes called “chocolate cysts.”

Filmy adhesions are thin bands of scar tissue that form in response to the body’s attempts to protect itself from the inflammation caused by endometriosis. (They can also form because of the surgeries used to diagnose and treat it.)

Adhesions tend to make organs to stick together, which can cause sharp, stabbing pain, as well as other symptoms depending on their location. For example, when on the reproductive organs, adhesions can make it harder for someone to get pregnant.

Adhesions on the bowel may lead to gastrointestinal symptoms, such as nausea.

 Stage 4 Endometriosis

Stage 4 endometriosis is the most severe. At this stage, there are:

  • A large number of cysts
  • Severe adhesions

While some types of cysts go away on their own, the cysts that form as a result of endometriosis usually need to be surgically removed. They can grow to be quite large, even as big as a grapefruit.

Small cysts on the back wall of the uterus and rectum may also be found at this stage. People with endometriosis in these areas may experience painful bowel movements, abdominal pain, constipation, nausea, and vomiting.

If endometrial lesions, cysts, or scar tissue is blocking one or both fallopian tubes, a person with endometriosis may experience infertility. Sometimes, trouble conceiving is the only symptom of endometriosis a person has.

Diagnosis: The only definitive way to diagnose endometriosis is by a laparoscopy – an operation in which a camera (a laparoscope) is inserted into the pelvis via a small cut near the navel. It is important that proper diagnosis is done since symptoms of endometriosis can be similar to and confused with symptoms of other conditions, such as pelvic inflammatory disease, ovarian cysts among others. Most women do not know about endometriosis until they are diagnosed through laparoscopy and this is usually initiated when the disease has spread widely in the reproductive system. The challenge is that laparoscopy surgery is very expensive and out of the reach of the majority of affected Kenyan women

Prevalence: Endometriosis affects 10% of women in the reproductive-age group (Eskenazi and Warner, 1997). This incidence increases up to 30% in patients with infertility (Italiano, 1994).

Impact of endometriosis on women’s lives: Endometriosis has a negative impact on marital/sexual relationships, social life, and on physical and psychological aspects in all the affected women. Other major impacts are on education for young women aged between 16–24 years, life opportunities and employment for women between 25–34 years while those aged 35 years and above face negative financial impact (Moradi et al., 2014). The economic burden of this disease is also high and similar to other chronic diseases such as diabetes, Crohn’s disease and rheumatoid arthritis (Simeons et al., 2012).

Association between endometriosis and cancer: The risk for cancer among women with endometriosis is elevated by 90% for ovarian cancer, 40% for hematopoietic cancer (primarily non-Hodgkin’s lymphoma), and 30% for breast cancer. Having a longer history of endometriosis and being diagnosed at a young age are both associated with increased cancer risk (Brinton et al 1997). Dr. Louise Brinton, Chief of the Hormonal and Reproductive Epidemiology branch at the National Cancer Institute, USA suggests that if endometriosis does increase the risk for ovarian cancer, then treating it might reduce this risk. Thus removing endometriosis should theoretically reduce the risk for cancer.


Albert L Hsu, MD1, IzabellaKhachikyan, MD1, and Pamela Stratton, MD1: Invasive and non-invasive methods for the diagnosis of endometriosis. ClinObstet Gynecol. 2010 June ; 53(2): 413–419

Brinton LA, Sakoda LC, Sherman ME, et al. Relationship of benign gynecologic diseases to subsequent risk of ovarian and uterine tumors. Cancer Epidemiol Biomarkers Prev. 2005;14:2929-2935

Brinton LA, Gridley G, Persson I, Baron J, Bergqvist A. Cancer risk after a hospital discharge diagnosis of endometriosis. Am J Obstet Gynecol. 1997;176:572-529. 

DeLigdisch L, Pénault-Llorca F, Schlosshauer P, Altchek A, Peiretti M, Nezhat F. Stage I ovarian carcinoma: different clinical pathologic patterns. FertilSteril. 2007;88:906-910.

Eskenazi B, Warner ML: Epidemiology of endometriosis. ObstetGynecolClin North Am 1997, 24:235-358.

Fader AN, Arriba LN, Frasure HE, von Gruenigen VE. Endometrial cancer and obesity: epidemiology, biomarkers, prevention and survivorship. GynecolOncol. 2009;114:121–7.

Friedenreich CM, Neilson HK, Lynch BM. State of the epidemiological evidence on physical activity and cancer prevention.Eur J Cancer. 2010;46:2593–604

GruppoItaliano: Prevalence and anatomical distribution of endometriosis in women with selected gynecological conditions: results from a multicentric Italian Study. Gruppoitaliano per lo studio dell’endometriosi. Hum Reprod 1994, 9:1158-1162.

Hennessy BT, Coleman RL, Markman M. Ovarian cancer.Lancet. 2009;374:1371Y1382.

Ness RB, Cramer DW, Goodman MT, et al. Infertility, fertility drugs, and ovarian cancer: a pooled analysis of case-control studies. Am J Epidemiol. 2002;155:217-224. 

Lynn Sterling, Luc van Lonkhuijzen,  JobNyangena, ElkanahOrango, Matthew Strother, NafthaliBusakhala and Barry Rosen. Protocol Development for Ovarian Cancer Treatment in Kenya. International Journal of Gynecological Cancer, 2011, DOI:10.1097/IGC.0b013e3182060316

Maryam Moradi, Melissa Parker, Anne Sneddon, Violeta Lopez and David Ellwood.  Impact of endometriosis on women’s lives: a qualitative study BMC Women’s Health 2014, 14:123

Renehan AG, Tyson M, Egger M, Heller RF, Zwahlen M. Body-mass index and incidence of cancer: a systematic review and meta-analysis of prospective observational studies. Lancet. 2008;371:569–78.

Sampson JA: Peritoneal endometriosis is due to menstrual disseminationof endometrial tissue into the peritoneal cavity.Am J ObstetGynecol1927, 14:422-469.

Simoens S, Dunselman G, Dirksen C, Hummelshoj L, Bokor A, Brandes I, D’Hooghe T: The burden of endometriosis: costs and quality of life of women with endometriosis and treated in referral centres. Hum Reprod 2012, 27(5):1292–1299.