What is endometriosis? A Mayo Clinic expert explains

Learn more about endometriosis from Megan Wasson, D.O., a minimally invasive gynecologic surgeon at Mayo Clinic.

Hi, I'm Dr. Megan Wasson, a minimally invasive gynecologic surgeon at Mayo Clinic. In this video, we will cover the basics of endometriosis, including what is it, who gets it, as well as the symptoms, diagnosis and treatment. Whether you are looking for answers for yourself or someone you love, we are here to give you the best information available. Endometriosis is a condition in which cells similar to the lining of the uterus, or endometrium, grow outside the uterus. Endometriosis often involves the pelvic tissue and can envelop the ovaries and fallopian tubes. It can affect nearby organs, including the bowel and bladder. So during the menstrual cycle, or period, this tissue responds to hormones, and due to its location, frequently results in pain. Endometriosis causes surrounding tissues to become irritated and potentially develop scars and sticky fibers that bind tissues together. In some cases, endometriosis can cause cysts on the ovaries. These are called endometriomas. Fortunately, there are effective treatments to manage and treat endometriosis.

Who gets it?

There are some possible explanations of what sparks the endometrial-like tissue to grow out of place. But the exact cause is still uncertain. However, there are some factors that make someone more likely to get endometriosis, such as never giving birth, menstrual cycles occurring more frequently than every 28 days, heavy and prolonged menstrual periods that lasts longer than seven days, having higher levels of estrogen in your body, having a low body mass index, having a structural issue with the vagina, cervix, or uterus that prevents the passage of menstrual blood from the body, a family history of endometriosis, starting your period at an early age, or starting menopause at an older age.

What are the symptoms?

The most common symptom of endometriosis is pelvic pain, either during or outside of the normal menstrual period that is beyond normal cramping, Normal menstrual cramping should be tolerable and should not require someone to miss time from school, work or normal activities. Other symptoms include cramps that begin before and extend after a menstrual period, lower back or abdominal pain, pain with intercourse, pain with bowel movements or urination, and infertility. Individuals with endometriosis may experience fatigue, constipation, bloating, or nausea, especially during periods. If you are feeling these symptoms, it's a good idea to talk to your health care provider.

How is it diagnosed?

First, your provider will ask you to describe your symptoms, including the location of the pelvic pain. Next, they may do a pelvic exam, an ultrasound, or an MRI to get a clearer view of the reproductive organs, including the uterus, ovaries, and fallopian tubes. To definitively diagnose endometriosis, surgery is required. This is most commonly performed by laparoscopy. The patient is under general anesthesia while the surgeon inserts a camera into the abdomen through a small incision to evaluate for endometrial-like tissue. Any tissue that looks like endometriosis is removed and examined under the microscope to confirm the presence or absence of endometriosis.

How is it treated?

When it comes to treating endometriosis, first steps involve trying to manage symptoms through pain medications or hormone therapy. Hormones, such as birth control pills, control the rise and fall of estrogen and progesterone in the menstrual cycle. If those initial treatments fail and symptoms are impacting a person's quality of life, surgery to remove endometriosis tissue may be considered.

What now?

Dealing with endometriosis, its pain, complications and fertility problems can be hard to cope with and be stressful. Consider joining a support group of people who can relate to what you are going through. If you'd like to learn even more about endometriosis, watch our other related videos or visit mayoclinic.org. We wish you well.

Endometriosis (en-doe-me-tree-O-sis) is an often-painful condition in which tissue that is similar to the inner lining of the uterus grows outside the uterus. It often affects the ovaries, fallopian tubes and the tissue lining the pelvis. Rarely, endometriosis growths may be found beyond the area where pelvic organs are located.

Endometriosis tissue acts as the lining inside the uterus would — it thickens, breaks down and bleeds with each menstrual cycle. But it grows in places where it doesn't belong, and it doesn't leave the body. When endometriosis involves the ovaries, cysts called endometriomas may form. Surrounding tissue can become irritated and form scar tissue. Bands of fibrous tissue called adhesions also may form. These can cause pelvic tissues and organs to stick to each other.

Endometriosis can cause pain, especially during menstrual periods. Fertility problems also may develop. But treatments can help you take charge of the condition and its complications.


The main symptom of endometriosis is pelvic pain. It's often linked with menstrual periods. Although many people have cramping during their periods, those with endometriosis often describe menstrual pain that's far worse than usual. The pain also may become worse over time.

Common symptoms of endometriosis include:

  • Painful periods. Pelvic pain and cramping may start before a menstrual period and last for days into it. You also may have lower back and stomach pain. Another name for painful periods is dysmenorrhea.
  • Pain with sex. Pain during or after sex is common with endometriosis.
  • Pain with bowel movements or urination. You're most likely to have these symptoms before or during a menstrual period.
  • Excessive bleeding. Sometimes, you may have heavy menstrual periods or bleeding between periods.
  • Infertility. For some people, endometriosis is first found during tests for infertility treatment.
  • Other symptoms. You may have fatigue, diarrhea, constipation, bloating or nausea. These symptoms are more common before or during menstrual periods.

The seriousness of your pain may not be a sign of the number or extent of endometriosis growths in your body. You could have a small amount of tissue with bad pain. Or you could have lots of endometriosis tissue with little or no pain.

Still, some people with endometriosis have no symptoms. Often, they find out they have the condition when they can't get pregnant or after they get surgery for another reason.

For those with symptoms, endometriosis sometimes may seem like other conditions that can cause pelvic pain. These include pelvic inflammatory disease or ovarian cysts. Or it may be confused with irritable bowel syndrome (IBS), which causes bouts of diarrhea, constipation and stomach cramps. IBS also can happen along with endometriosis. This makes it harder for your health care team to find the exact cause of your symptoms.

When to see a doctor

See a member of your health care team if you think you might have symptoms of endometriosis.

Endometriosis can be a challenge to manage. You may be better able to take charge of the symptoms if:

  • Your care team finds the disease sooner rather than later.
  • You learn as much as you can about endometriosis.
  • You get treatment from a team of health care professionals from different medical fields, if needed.

Women’s health topics - straight to your inbox

Get the latest information from our Mayo Clinic experts on women’s health topics, serious and complex conditions, wellness and more. Click to view a preview and subscribe below.

To provide you with the most relevant and helpful information, and understand which information is beneficial, we may combine your email and website usage information with other information we have about you. If you are a Mayo Clinic patient, this could include protected health information. If we combine this information with your protected health information, we will treat all of that information as protected health information and will only use or disclose that information as set forth in our notice of privacy practices. You may opt out of email communications at any time by clicking on the unsubscribe link in the email.


The exact cause of endometriosis isn't clear. But some possible causes include:

  • Retrograde menstruation. This is when menstrual blood flows back through the fallopian tubes and into the pelvic cavity instead of out of the body. The blood contains endometrial cells from the inner lining of the uterus. These cells may stick to the pelvic walls and surfaces of pelvic organs. There, they might grow and continue to thicken and bleed over the course of each menstrual cycle.
  • Transformed peritoneal cells. Experts suggest that hormones or immune factors might help transform cells that line the inner side of the abdomen, called peritoneal cells, into cells that are like those that line the inside of the uterus.
  • Embryonic cell changes. Hormones such as estrogen may transform embryonic cells — cells in the earliest stages of development — into endometrial-like cell growths during puberty.
  • Surgical scar complication. Endometrial cells may attach to scar tissue from a cut made during surgery to the stomach area, such as a C-section.
  • Endometrial cell transport. The blood vessels or tissue fluid system may move endometrial cells to other parts of the body.
  • Immune system condition. A problem with the immune system may make the body unable to recognize and destroy endometriosis tissue.

Risk factors

Factors that raise the risk of endometriosis include:

  • Never giving birth.
  • Starting your period at an early age.
  • Going through menopause at an older age.
  • Short menstrual cycles — for instance, less than 27 days.
  • Heavy menstrual periods that last longer than seven days.
  • Having higher levels of estrogen in your body or a greater lifetime exposure to estrogen your body produces.
  • Low body mass index.
  • One or more relatives with endometriosis, such as a mother, aunt or sister.

Any health condition that prevents blood from flowing out of the body during menstrual periods also can be an endometriosis risk factor. So can conditions of the reproductive tract.

Endometriosis symptoms often happen years after menstruation starts. The symptoms may get better for a time with pregnancy. Pain may become milder over time with menopause, unless you take estrogen therapy.



The main complication of endometriosis is trouble getting pregnant, also called infertility. Up to half of people with endometriosis have a hard time conceiving.

For pregnancy to happen, an egg must be released from an ovary. Then the egg has to travel through the fallopian tube and become fertilized by a sperm cell. The fertilized egg then needs to attach itself to the wall of the uterus to start developing. Endometriosis may block the tube and keep the egg and sperm from uniting. But the condition also seems to affect fertility in less-direct ways. For instance, it may damage the sperm or egg.

Even so, many with mild to moderate endometriosis can still conceive and carry a pregnancy to term. Health care professionals sometimes advise those with endometriosis not to delay having children. That's because the condition may become worse with time.


Some studies suggest that endometriosis raises the risk of ovarian cancer. But the overall lifetime risk of ovarian cancer is low to begin with. And it stays fairly low in people with endometriosis. Although rare, another type of cancer called endometriosis-associated adenocarcinoma can happen later in life in those who've had endometriosis.

Oct. 12, 2023
  1. Endometriosis. Office on Women's Health. https://www.womenshealth.gov/publications/our-publications/fact-sheet/endometriosis.html. Accessed March 22, 2023.
  2. Schenken RS. Endometriosis: Pathogenesis, epidemiology, and clinical impact. https://www.uptodate.com/contents/search. Accessed March 22, 2023.
  3. FAQs: Endometriosis. American College of Obstetricians and Gynecologists. https://www.acog.org/womens-health/faqs/endometriosis. Accessed March 22, 2023.
  4. AskMayoExpert. Endometriosis. Mayo Clinic; 2022.
  5. Smith RP. Endometriosis. In: Netter's Obstetrics and Gynecology. 3rd ed. Elsevier; 2018. https://www.clinicalkey.com. Accessed March 22, 2023.
  6. What is assisted reproductive technology? Centers for Disease Control and Prevention. https://www.cdc.gov/art/whatis.html. Accessed March 22, 2023.
  7. Schenken RS. Endometriosis: Treatment of pelvic pain. https://www.uptodate.com/contents/search. Accessed March 22, 2023.
  8. Lebovic DI. Endometriosis: Surgical management of pelvic pain. https://www.uptodate.com/contents/search. Accessed March 22, 2023.
  9. Strauss JF, et al., eds. Endometriosis. In: Yen and Jaffe's Reproductive Endocrinology. 8th ed. Elsevier; 2019. https://www.clinicalkey.com. Accessed March 22, 2023.
  10. Lobo RA, et al. Endometriosis etiology, pathology, diagnosis, management. In: Comprehensive Gynecology. 8th ed. Elsevier; 2022. https://www.clinicalkey.com. Accessed March 22, 2023.
  11. What are the symptoms of endometriosis? National Institutes of Health. https://www.nichd.nih.gov/health/topics/endometri/conditioninfo/symptoms. Accessed March 22, 2023.
  12. Tuesley KM, et al. Hysterectomy with and without oophorectomy and all-cause and cause-specific mortality. American Journal of Obstetrics and Gynecology. 2020; doi: 10.1016/j.ajog.2020.04.037.
  13. Burnett TL (expert opinion). Mayo Clinic, Rochester, Minn. June 15, 2018.
  14. Warner KJ. Allscripts EPSi. Mayo Clinic. May 11, 2021.
  15. Mira TAA, et al. Systematic review and meta-analysis of complementary treatments for women with symptomatic endometriosis. International Journal of Gynecology and Obstetrics. 2018;143:2.
  16. Nabi MY, et al. Endometriosis and irritable bowel syndrome: A systematic review and meta-analyses. Frontiers in Medicine. 2022; doi:10.3389/fmed.2022.914356.
  17. Schenken RS. Endometriosis: Clinical features, evaluation, and diagnosis. https://www.uptodate.com/contents/search. Accessed March 23, 2023.
  18. FAQs: Laparoscopy. American College of Obstetricians and Gynecologists. https://www.acog.org/womens-health/faqs/endometriosis. Accessed March 23, 2023.
  19. Abril-Coello R, et al. Benefits of physical therapy in improving quality of life and pain associated with endometriosis: A systematic review and meta-analysis. International Journal of Gynecology & Obstetrics. 2022; doi:10.1002/ijgo.14645.