Endometriosis 101
What Is It
Endometriosis is a condition in which tissue similar to the lining of the uterus grows outside of the uterus. The term lesions refers to areas of tissue that have grown where they don’t belong; in this case, patches of endometrial-like cells (the type that normally line the inside of the uterus) that have implanted in other places. Lesions typically develop in the pelvis and abdomen and are commonly found in areas such as the space between the uterus and rectum (pouch of Douglas), the ligaments around the uterus (uterosacral ligaments), ovaries, fallopian tubes, and the lining of the pelvic cavity. Less commonly, they can appear on the bladder, rectum, vagina, intestines, appendix, or spinal nerves. In rare cases, they may even spread beyond the pelvis to organs like the kidneys, lungs, diaphragm, or brain.
These lesions still respond to monthly hormonal changes. When estrogen levels ride, they can grow and thicken, just like the uterine lining does before a period. But because this tissue is outside of the uterus, it has nowhere to go when it breaks down, leading to inflammation and irritation in the surrounding areas.
Over time, this repeated inflammation can cause:
Adhesions: bands of sticky scar-like tissue that cause organs to stick together
Scarring: thickening or stiffening of tissue where inflammation has healed over multiple cycles
Internal bleeding: small amounts of bleeding inside the pelvis when these lesions break down each month, which can trigger pain and swelling.
Together, these changes can lead to pelvic pain, cramping, bloating, and other symptoms commonly seen in conditions like endometriosis and adenomyosis.
It’s important to clarify a common misconception: endometriosis is NOT a menstruation or gynecological disease. Let me say that again for emphasis: IT IS NOT A MENSTRUATION OR GYNECOLOGICAL DISEASE. Endometriosis is a complex, systemic, inflammatory condition that affects the whole body and can be debilitating.
Statistics
Endometriosis affects roughly 1 in 10 women in the U.S. While treatable, there is no known cause or cure. Due to gaps in research and education on women’s health, symptoms are often misdiagnosed or dismissed. This can lead to significant delays in diagnosis, typically 7–10 years. Imagine experiencing severe pain daily, navigating other symptoms, and spending years searching for answers while trying to find someone who believes you. Millions of women face this reality.
As Amy Schumer once said, “They have chewable Viagra, but they can’t throw us a bone with endometriosis?” Thanks for the advocacy, queen.
Symptoms
Symptoms of endometriosis include:
Abnormal periods
Painful periods
Pain with intercourse
Pain with urination and/or bowel movements
Fatigue
Gastrointestinal distress
Low back / leg pain
Infertility
Everyone’s experience is different. Some women may have several symptoms, all of them, or none. Severe symptoms don’t always correlate with severe disease, and vice versa.
Stages
The American Society of Reproductive Medicine (ASRM) developed the most commonly used staging system. It divides endometriosis into four stages based on lesion number and depth, using a points system:
ASRM Endometriosis Stages
Stage I (1–5 points): Minimal — few superficial implants
Stage II (6–15 points): Mild — more and deeper implants
Stage III (16–40 points): Moderate — many deep implants, small ovarian cysts, filmy adhesions
Stage IV (>40 points): Severe — many deep implants, large ovarian cysts, dense adhesions
While helpful, this system doesn’t indicate pain, fertility issues, or lesion location. The Endometriosis Foundation of America (EndoFound) proposed a classification based on location and infiltration depth:
EndoFound Classification
Category I: Peritoneal Endometriosis — minimal, affects the peritoneum lining the abdomen
Category II: Ovarian Endometriomas (Chocolate Cysts) — established in ovaries, may rupture and spread
Category III: Deep Infiltrating Endometriosis I (DIE I) — affects pelvic organs, can distort pelvic anatomy
Category IV: Deep Infiltrating Endometriosis II (DIE II) — affects organs inside and outside the pelvis, including bowels, appendix, diaphragm, heart, and lungs
What causes it
Shockingly (I hope you can hear the sarcasm here), the cause of endometriosis is still unknown, mostly due to lack of research. In 2013, a study looked at the “attractiveness” of women with endometriosis rather than its cause, cure, or underlying biology. Eye-roll worthy, to say the least.
Despite the lack of a definitive cause (or causes - there is likely more than one), there are some proposed theories:
Retrograde menstruation
During menstruation, some menstrual blood containing endometrial cells can travel backward through the fallopian tubes into the pelvic cavity instead of leaving the body. These displaced cells may then attach to surrounding tissues, leading to the implantation and growth of endometriosis lesions.
Immunologic
Another theory suggests that endometriosis may be linked to immune system dysfunction. Antibodies against endometrial cells have been found in the blood, triggering inflammation and damage to surrounding tissues. However, it remains unclear whether these immune changes cause endometriosis or occur as a result of the condition itself.
Genetic
A family history of endometriosis significantly increases risk (up to sevenfold) indicating a genetic component. While no specific gene has been identified, the condition appears to result from multiple genetic and environmental factors
Genetic/Epigenetic
Recent evidence indicates that endometriotic lesions may arise from endometrial, bone marrow, or stem cells with genetic or epigenetic abnormalities. These microscopic lesions can regress or progress depending on additional factors, resembling how certain tumors form.
How Is It Diagnosed
Recent guidelines indicate that endometriosis can often be diagnosed based on clinical symptoms and imaging findings, although laparoscopy remains the gold standard for confirmation. While imaging and symptom patterns can strongly suggest the condition, surgery is still required for a definitive diagnosis.
Ultrasound and MRI are useful for identifying endometriomas and deep infiltrating lesions. However, the more common peritoneal implants (stage I–II) are typically too small to be detected without surgery.
How Is It Treated
Treatment for endometriosis generally includes two main approaches: medication to regulate hormonal activity and surgery to remove endometrial-like tissue. If symptoms continue despite medical management, surgical excision of the lesions may be recommended.
Final Thoughts
Endometriosis affects millions of women worldwide, yet it remains misunderstood and under-researched. Educating yourself, seeking care from knowledgeable providers, and connecting with others who understand your experience can make a meaningful difference. You deserve to be heard, supported, and taken seriously every step of the way.
While women are working to make sure that their voices are heard and their symptoms are not dismissed, it seems like we still have a long way to go. So I urge you to continue to advocate for yourself and to fight for the care you deserve. And if you decide to work with me, which I sincerely hope you do, I promise to fight for you, too.
