Endometriosis 101

Endometriosis 101

Endometriosis is a medical condition where endometrial-like tissue (similar in structure to the tissue that lines the uterus and sheds during a period) is found outside of the uterus. The extrauterine endometrial-like tissue (lesions) are typically found in the pelvic cavity (on the bladder, rectum, or ovaries) as well as the bowel, diaphragm, and pleural cavity.

Endometriosis is one of the most common gynecological diseases, yet there is still a lot unknown about this condition and it is often misdiagnosed. The symptoms of endometriosis are widely variable and many mimic other gynecologic conditions. Among women* in Canada, there is a reported 5.4 year delay in diagnosis following the onset of symptoms. 

It is estimated that 1 in every 10 people with a uterus has or will develop endometriosis. However, this is likely an underestimate because the only way to officially diagnose endometriosis is with surgery. Endometriosis is a chronic disease meaning it requires lifelong management. 


Endometrial tissue is hormone responsive, meaning that the tissue grows and sheds in response to fluctuations of hormone levels within the body. One influential hormone is estrogen, which causes endometrial and endometrial-like tissue to grow. When the endometrium-like tissue grows it can create inflammation in surrounding tissue and, much like endometrium inside the uterus during a menstrual cycle, these lesions can shed and bleed. This creates scar tissue and adhesions (a band of scar tissue that connects two surfaces not usually connected).

Lesions cause pain and other symptoms depending on their location creating a broad constellation of symptoms that individuals with endometriosis may experience in any combination or they may not experience any symptoms. This makes endometriosis difficult to recognize and diagnose. 


  • Chronic abdominal or pelvic pain/pressure
  • Severe pain during menstruation (dysmenorrhea)
  • Pain with sex (dyspareunia)
  • Heavy menstrual bleeding
  • Bowel and bladder dysfunction (pain or changes in urgency and/or frequency)
  • Infertility 


There is uncertainty about the cause of endometriosis but family history, nulliparity (never being pregnant), and retrograde menstruation have all been shown to increase risk of developing the disease. 


While the exact mechanism of infertility among individuals with endometriosis is uncertain there is a clear link as almost 4 in 10 women* with infertility have endometriosis and up to 50% of women with endometriosis experience infertility

It is hypothesized that there are multiple causes depending on the stage of disease (a system used to classify disease severity). For individuals with stage I (minimal) or II (mild) endometriosis, fertility is thought to be impacted by chronic inflammation. Stage III or IV (advanced) endometriosis is associated with changes in pelvic anatomy and adhesions creating physical barriers to fertility in addition to chronic inflammation. 


The approach to diagnosis is a multi-step process that requires discussion between an individual and their doctor

Physical or pelvic exams and imaging (with ultrasound or MRI) are often unreliable for diagnosis of endometriosis due to the variation in location and size of lesions. However, providers may make a presumptive clinical diagnosis based on symptoms, physical exam findings, and imaging. The only definitive way to diagnose endometriosis is with a surgical procedure called a laparoscopy. This allows for visualization and confirmational sampling (biopsy) of endometrial lesions. 

Treatment of endometriosis is also individualized based on a multitude of factors including symptoms and severity, extent and location of lesions, and reproductive desires. Options include medication, surgery, or a combination. 

For individuals with mild to moderate symptoms and those who prefer to avoid surgery, current medical guidelines recommend trials of low-risk medication such as nonsteroidal anti-inflammatory drugs (NSAIDs), acetaminophen/paracetamol, and hormonal contraception (estrogen-progestin contraceptives and progestins)5. Symptoms should be reassessed after 3-4 months of treatment to evaluate for effectiveness. 

For individuals with severe symptoms or persistent symptoms despite a trial of the low-risk medications previously discussed, additional medications such as gonadotropin-releasing hormone (GnRH) analogs and aromatase inhibitors may be considered. Surgery may also be utilized for treatment and options for surgical interventions depend on lesion location, size, and individual desire for fertility. 


Ultimately, diagnosis and treatment are highly personalized processes for an individual and their doctor to navigate. If you are experiencing symptoms like the ones discussed in this article (or any that feel abnormal for your body) it may be beneficial to discuss this with a physician. While the road to diagnosis can be long, know that you are not alone. 

Below are additional resources for endometriosis education and support:

www.endometriosis.org – A nonprofit website dedicated to information about endometriosis and treatment

European Society of Human Reproductive and Embryology Guidelines: Endometriosis

American College of Obstetrics and Gynecologists Endometriosis FAQ

Center for Young Women’s Health – Informational site sponsored by Boston Children’s Hospital

American Society for Reproductive Medicine – Free materials on reproductive health issues

The Endometriosis Association – An independent, nonprofit, self-help organization of women with endometriosis, clinicians, and others interested in the disease

*The term “women” is used to reflect the population that participated in the study this data comes from. We acknowledge that not everyone with a uterus experiencing infertility identifies as a woman and strive to use gender-inclusive language.

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