Endometriosis occurs when tissue that normally lines the inside of the uterus starts growing outside of the uterus, where it doesn't belong.
This out-of-place tissue, often called a lesion or an implant, can cause severe pain and inflammation throughout the month.
The symptoms of endometriosis are different for every woman
The 3 most common symptoms include:
- Painful periods
- Pelvic pain in between periods
- Pain with sex
But women with endometriosis can experience a variety of different symptoms.
The exact cause of endometriosis is unknown
One popular theory as to what causes endometriosis is something called retrograde menstruation, which is when, during menstruation, the lining of the uterus flows in the opposite direction of the way it’s supposed to. But it’s not certain this is the cause. Learn more about retrograde menstruation and explore other possible causes of endometriosis
Symptoms may depend on where the endometrial lesions are located
The location of endometrial lesions can affect what kind of symptoms a woman experiences. For example, if she has lesions on her bladder, she may have pain while urinating. Learn more about the different places lesions may develop and the symptoms they can cause
Stages of endometriosis
Endometriosis is described as having 4 stages. Doctors classify these stages as:
- Stage 1 – minimal
- Stage 2 – mild
- Stage 3 – moderate
- Stage 4 – severe
But it’s important to know that these stages have nothing to do with how painful the disease is. For example, a woman with stage 1 endometriosis might have severe pain, while a woman with stage 4 may have no pain at all.
Instead, the stages have to do with the size of the endometrial lesions, their location in the body, the number of them, and their depth (whether they're on the surface of an organ or deep within it).
References: 1. American College of Obstetricians and Gynecologists. Practice bulletin no. 114: management of endometriosis. Obstet Gynecol. 2010;116(1):223-236. 2. American College of Obstetricians and Gynecologists. Frequently asked questions. FAQ013. Gynecologic problems. https://www.acog.org/~/media/For%20Patients/faq013.pdf?dmc=1. Updated October 2012. Accessed January 8, 2020. 3. Fischer JR. APGO Educational Series on Women’s Health Issues. Diagnosis & management of endometriosis: pathophysiology to practice. Association of Professors of Gynecology and Obstetrics; 2012. 4. Liu JH. Merck Manuals. Consumer Version. Women’s Health Issues. Endometriosis. https://www.merckmanuals.com/home/women-s-health-issues/endometriosis/endometriosis. Updated February 2019. Accessed January 8, 2020. 5. American Society for Reproductive Medicine. ASRM Patient Information Series. Endometriosis—a guide for patients; revised 2012. 6. Giudice LC. Clinical practice: endometriosis. N Engl J Med. 2010;362(25):2389-2398.