What is endometriosis?

Endometriosis is a condition in which the tissue that’s usually on the inside of the uterus grows on the outside of the uterus as well. Endometriosis can cause pelvic pain that can range from mild to severe, and can interfere with fertility when trying to conceive.

Endometriosis is extremely common, as according to the American College of Obstetricians and Gynecologists, it affects around 1 in 10 women of reproductive age. It can show up as early as in the first few years after puberty, but often occurs later, and usually is diagnosed in women in their 30s and 40s.

Signs and symptoms

Pelvic pain is the most common, defining symptom of endometriosis, but it isn’t the only one. Other common symptoms of endometriosis include:

  • Heavy bleeding: Since the endometrial tissue on the outside of the uterus still acts like it would if it was on the inside of the uterus, thickening before breaking down into blood at each menstrual cycle, endometriosis can cause either unusually heavy bleeding during periods or some bleeding between periods.
  • Pelvic cramps: During or leading up to menstruation, endometriosis can cause cramps that are stronger or more painful than usual.
  • Painful sex: Pelvic pain from endometriosis can also show up as painful sexual intercourse.
  • Painful urination or bowel movements: Especially during menstruation, endometriosis can cause painful urination or bowel movements.
  • Infertility: Somewhere between one-third and half of all women with endometriosis experience infertility. Endometriosis interferes with fertility when the endometrial tissue in the fallopian tube gets in the way of the sperm and the egg meeting each other. Endometriosis may also cause damage to the sperm or the egg less directly.
  • Other symptoms: Endometriosis may also cause other symptoms that aren’t always easy to distinguish from a regular period, like fatigue, constipation, diarrhea, bloating, or nausea, most commonly during menstruation.


It’s not certain exactly what causes endometriosis. There are a few theories for what might cause it, though. The three most common theories are:

  • Sampson’s theory: The theory that the Mayo Clinic describes as the most likely cause of endometriosis, it suggests that endometriosis happens when, during menstruation, menstrual blood which includes endometrial cells gets backed up, and flows backwards up the fallopian tube and into the pelvic cavity. Then, those endometrial cells attach themselves to the outside of the uterus, where they grow.
  • Meyer’s theory: Suggesting that the endometriosis comes from the same cells that have been on the outside of the uterus all along, this theory asserts that the cells that have been there since birth, can sometimes change into endometrial cells, and as those endometrial cells grow, they can turn into endometriosis.
  • Vascular theory: This theory states that the endometrial cells that start out inside the uterus, exactly where they’re supposed to be, can travel to different parts of the body through the blood vessels. If they make it into the abdomen through the blood vessels, they can implant on the outside of the uterus and start to grow.

Other possible causes in some cases are endometrial cells implanting themselves into the outside of the uterus through a surgical incision after a C-section or hysterectomy, or an immune system disorder that could make it hard for the body to fight against endometrial cells trying to implant themselves where they shouldn’t.


Endometriosis can be suspected based on symptoms, but the only way for it to be definitely diagnosed is surgically, through a laparoscopy. Other tests to rule out other possible causes will probably be run first, including a pelvic exam, ultrasound, blood tests, and vaginal cultures to check for infection.

In a laparoscopy, the laparoscope, a thin tube that allows the doctor to look inside the body, is passed into the abdomen through an incision. The doctor can then look at the outside of the uterus, ovaries, fallopian tubes, and other nearby organs. There may be a second incision to pass surgical instruments through, or surgical instruments can be attached to the laparoscope to take tissue samples or remove scar tissue.


Depending on how strong the symptoms of endometriosis are, there are several different courses of treatment that may be recommended.

  • Observation and lifestyle changes: For women whose symptoms are mild, especially young women, simple observation is often an early starting point for treatment. On the other hand, women who are diagnosed with endometriosis partially because they’re having trouble conceiving may prefer a more active treatment. Lifestyle changes that can help manage endometriosis pain during observation include a healthy diet, getting enough rest, and even relaxation techniques. Healthcare providers may also recommend over-the-counter pain relievers like ibuprofen or naproxen products.
  • Surgery during diagnosis: During the laparoscopy to diagnose endometriosis, the doctor may cut or burn away endometrial lesions, especially in early or less extensive cases. Endometriosis that covers a larger area may be harder to treat this way. This treatment is shown to reduce pain in most patients, and though it’s less clear whether it improves fertility, some evidence suggests it could.
  • Hormone therapy: Hormone therapy can reduce pain in endometriosis patients, though it isn’t a permanent fix, and symptoms can come back after stopping treatment. Hormones can be effective for managing endometriosis since it’s hormones that cause endometrial tissue to thicken, break down, and bleed. Targeted hormonal treatment can do the opposite, and slow endometrial growth, though this treatment generally isn’t compatible with trying to conceive.
  • Hysterectomy: Endometriosis generally ends on its own at menopause in women who aren’t taking additional hormonal medication. A full hysterectomy, which includes the removal of the uterus and the cervix, as well as the removal of both ovaries, has the same effect. This is generally considered a last resort treatment, since not only is it not possible to become pregnant after, but it’s also a highly invasive surgery.


While hormone therapy and laparoscopy can’t cure endometriosis, they can relieve the symptoms for years. A hysterectomy gives the best chance of a full cure, as does menopause, for women who don’t continue to take hormonal medication.

However, pain management techniques can help endometriosis patients to live more comfortably with it, and in cases where endometriosis causes fertility problems, or even infertility, a healthcare provider may eventually recommend trying assisted reproductive technology like in vitro fertilization for women who are trying to conceive.

  • “Endometriosis.” MedlinePlus. U.S. National Library of Medicine, September 26 2016. Web.
  • “Endometriosis: Does It Cause Infertility?” ASRM. American Society of Reproductive Medicine, 2012. Web.
  • “Facts About Endometriosis.” IDPH. Illinois Department of Public Health. Web.
  • “FAQ: Endometriosis.” ACOG. American College of Obstetricians and Gynecologists, October 2012. Web.
  • “Endometriosis: A Guide for Friends, Siblings, and Significant Others.” Youngwomenshealth. Boston Children’s Hospital, July 30 2014. Web.
  • Mayo Clinic Staff. “Endometriosis.” Mayo Clinic. Mayo Clinic, April 2 2013. Web.
  • “Surgical Treatment for Endometriosis.” my.clevelandclinic. The Cleveland Clinic Foundation, 1995-2014. Web.
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