Endometriosis - symptoms and causes (2023)

General description

What is endometriosis? A Mayo Clinic expert explains

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

Hi, I'm Dr. Megan Wasson, a minimally invasive gynecologist at the Mayo Clinic. In this video, we'll cover the basics of endometriosis, including what it is, who gets it, and symptoms, diagnosis, and treatment. Whether you're looking for answers for yourself or a loved one, we're here to provide you with 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 involve 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, because of its location, often causes pain. Endometriosis causes irritation of the surrounding tissues and potentially the development of scars and sticky fibers that connect the tissues together. In some cases, endometriosis can cause ovarian cysts. These are called endometriomas. Fortunately, there are effective treatments to control and treat endometriosis.

Who gets it?

There are a few possible explanations for what causes endometrial-like tissue to grow out of place. But the exact cause is still uncertain. However, there are some factors that make a person more likely to develop endometriosis, such as never giving birth, menstrual cycles occurring more often than every 28 days, heavy and prolonged periods lasting more than seven days, having higher estrogen levels. in your body, have a low body mass index, have a structural problem with the vagina, cervix or uterus that prevents menstrual blood from passing through the body, a family history of endometriosis, starting periods at a young 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 a normal period that goes beyond normal cramping. Normal period cramps should be tolerable and should not require someone to miss time from school, work, or normal activities. Other symptoms include cramping that starts before and extends after menstruation, lower back or abdominal pain, pain during intercourse, pain with bowel movements or urination, and infertility. People with endometriosis may experience fatigue, constipation, bloating or nausea, especially during periods. If you experience these symptoms, it's a good idea to talk to your healthcare provider.

How is the diagnosis made?

First, your provider will ask you to describe your symptoms, including the location of your pelvic pain. They may then perform a pelvic exam, ultrasound or MRI to get a clearer picture of the reproductive organs, including the uterus, ovaries and fallopian tubes. A definitive diagnosis of endometriosis requires surgery. This is most often done by laparoscopy. The patient is under general anesthesia while the surgeon inserts a camera into the abdomen through a small incision to assess the endometrial-like tissue. Any tissue that looks like endometriosis is removed and examined under a microscope to confirm the presence or absence of endometriosis.

How is it treated?

When it comes to treating endometriosis, the first steps are to try to control symptoms with pain relievers or hormone therapy. Hormones, such as birth control pills, control the rise and fall of estrogen and progesterone in the menstrual cycle. If these initial treatments fail and symptoms affect a person's quality of life, surgery to remove the endometrial tissue may be considered.

And now what?

Dealing with endometriosis, pain, complications and fertility problems can be difficult and stressful. Consider joining a support group of people who can relate to what you're going through. If you want to learn more about endometriosis, check out our other related videos or visit mayoclinic.org. We wish you the best.


Endometriosis - symptoms and causes (1)


With endometriosis, parts of the lining of the uterus (endometrium), or endometrial-like tissue, grow outside the uterus into other pelvic organs. Outside the uterus, the tissue thickens and bleeds, just like typical endometrial tissue during menstrual cycles.

Endometriosis (en-doe-me-tree-O-sis) is an often painful disorder in which tissue similar to the tissue that normally lines the inside of the uterus, the endometrium, grows outside the uterus. Endometriosis most commonly affects the ovaries, fallopian tubes, and tissue lining the pelvis. Rarely, endometrial-like tissue can be found beyond the area where the pelvic organs are located.

With endometriosis, the endometrial-like tissue acts like endometrial tissue: it thickens, breaks down, and bleeds with each menstrual cycle. But because this tissue has no way out of your body, it gets trapped. When endometriosis affects the ovaries, cysts called endometriomas can form. The surrounding tissue can become irritated and eventually develop scar tissue and adhesions, bands of fibrous tissue that can cause pelvic tissues and organs to stick together.

Endometriosis can cause pain, sometimes severe, especially during menstruation. Fertility problems may also develop. Fortunately, there are effective treatments available.


The main symptom of endometriosis is pelvic pain, often associated with menstruation. Although many people experience cramping during their period, those with endometriosis often describe period pain that is much worse than usual. The pain may also increase over time.

Common signs and symptoms of endometriosis include:

  • Painful periods (dysmenorrhoea).Pelvic pain and cramps may start before and last several days after menstruation. You may also have lower back and abdominal pain.
  • Pain with intercourse.Pain during or after sex is common with endometriosis.
  • Pain during defecation or urination.You are more likely to experience these symptoms during a period.
  • Excessive bleeding.You may occasionally experience heavy periods or bleeding between periods (breakthrough bleeding).
  • Sterility.Endometriosis is sometimes first diagnosed in those seeking infertility treatment.
  • Other signs and symptoms.You may experience fatigue, diarrhea, constipation, bloating or nausea, especially during your period.

The severity of your pain may not be a reliable indicator of the extent of your condition. You could have mild endometriosis with severe pain, or you could have advanced endometriosis with little or no pain.

Endometriosis is sometimes confused with other conditions that can cause pelvic pain, such as pelvic inflammatory disease (PID) or ovarian cysts. It can be confused with irritable bowel syndrome (IBS), a condition that causes bouts of diarrhea, constipation and abdominal cramps. IBS can accompany endometriosis, which can complicate the diagnosis.

When to see a doctor

See your doctor if you have signs and symptoms that may indicate endometriosis.

Endometriosis can be a difficult condition to manage. Early diagnosis, a multidisciplinary medical team, and understanding your diagnosis can lead to better management of your symptoms.

Request an appointment

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Although the exact cause of endometriosis is not certain, possible explanations include:

  • Retrograde menstruation.In retrograde menstruation, menstrual blood containing endometrial cells flows back through the fallopian tubes into the pelvic cavity instead of exiting the body. These endometrial cells attach to the pelvic walls and surfaces of the pelvic organs, where they grow and continue to thicken and bleed during each menstrual cycle.
  • Peritoneal cell transformation.In what's known as the "induction theory," experts suggest that hormones or immune factors promote the conversion of peritoneal cells (cells that line the inside of the abdomen) into endometrial-like cells.
  • Embryonic cell transformation.Hormones such as estrogen can transform fetal cells (cells in the early stages of development) into endometrial-like cell implants during puberty.
  • Surgical scar implantation.After surgery, such as a hysterectomy or caesarean section, endometrial cells can become stuck to a surgical incision.
  • Endometrial cell transfer.Blood vessels or the fluid tissue (lymphatic) system can carry endometrial cells to other parts of the body.
  • Immune system disorder.A problem with the immune system can make the body unable to recognize and destroy endometrial tissue that grows outside the uterus.

Risk factors

Several factors put you at higher risk of developing endometriosis, including:

  • never give birth
  • Starting your period at an early age
  • You go through menopause at a later age
  • Short menstrual cycles, for example, less than 27 days.
  • Heavy menstrual periods lasting more than seven days.
  • Having higher levels of estrogen in your body or increased lifetime exposure to the estrogen your body makes
  • low body mass index
  • One or more family members (mother, aunt or sister) with endometriosis
  • Any medical condition that prevents blood from passing through the body during menstruation
  • disorders of the reproductive system

Endometriosis usually develops several years after the onset of menstruation (menarche). Signs and symptoms of endometriosis may improve temporarily with pregnancy and disappear completely with menopause, unless you are taking estrogen.



Fertilization and implantation

Endometriosis - symptoms and causes (2)

Fertilization and implantation

During fertilization, the sperm and egg unite in one of the fallopian tubes to form a zygote. The zygote then travels down the fallopian tube, where it develops into a nucleus. Once it reaches the uterus, the embryo becomes a blastocyst. The blastocyst then penetrates the lining of the uterus, a process called implantation.

The main complication of endometriosis is impaired fertility. About a third to a half of women with endometriosis have trouble getting pregnant.

For pregnancy to occur, an egg must be released from an ovary, travel through a nearby fallopian tube, be fertilized by a sperm, and attach to the wall of the uterus to begin development. Endometriosis can block the tube and prevent the egg and sperm from joining. But the condition also appears to affect fertility in less direct ways, such as by damaging the sperm or egg.

Even so, many with mild to moderate endometriosis are still able to conceive and carry a pregnancy to term. Doctors sometimes advise people with endometriosis not to delay having children because the condition can get worse over time.


Ovarian cancer occurs at higher rates than expected in people with endometriosis. But the overall lifetime risk of ovarian cancer is low to begin with. Some studies show that endometriosis increases this risk, but it is still relatively low. Although rare, another type of cancer, endometriosis-related adenocarcinoma, can develop later in life in those who have had endometriosis.

By the Mayo Clinic staff

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