What Is an Endometrioma?

An Ovarian Cyst Related to Endometriosis

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Endometriomas are cysts that can form when tissue from the lining of the uterus grows in the ovaries. They are part of a condition known as endometriosis. Endometriomas are also called "chocolate cysts" because they are filled with dark brown menstrual blood.

When you have endometriosis, endometrial tissue grows outside the uterus and into other areas of the abdomen/pelvic region.

This article explains the symptoms and causes of endometriomas. It also describes some of the possible complications and how these cysts are treated.

A woman with hands on her stomach and pelvic area while lying down

Ozgurcankaya / Getty Images

What Causes Endometriomas?

The cause of endometrioma isn't known for sure, but research suggests some may form as a result of retrograde menstruation. Retrograde menstruation may also contribute to endometriosis. Ovarian endometriomas are found in up to 17% to 44% of women with endometriosis.

In retrograde menstruation, some of a woman’s menstrual blood flows back into her body during her period instead of out through the cervix and vagina. The endometrial cells are carried backward through the fallopian tubes to the ovaries and pelvic cavity, where they implant and cause endometriosis.

With endometriomas, retrograde menstruation results in endometrial tissue being trapped in the cysts, causing inflammation.

Endometriomas are sometimes called "chocolate cysts" because they are filled with dark brown fluid consisting of old menstrual blood and tissue.

There is some evidence suggesting that an autoimmune response can contribute to endometriomas. In this case, the endometrial tissue that normally forms during menstruation would cause an inflammatory response that could lead to scarring and diseased tissue in the pelvis.

Are Endometriomas Dangerous?

Endometriomas are almost never dangerous. Rarely, however, a cancerous tumor may be misdiagnosed as an endometrioma. For this reason, cysts that are larger than 4 cm and don't resolve on their own are usually removed surgically. 

Symptoms of Endometriomas

Endometriomas may or may not cause symptoms. When symptoms do occur, they are the same as the symptoms of endometriosis.

These may include:


Among the possible complications of endometriomas are:

  • Infertility
  • Ovarian cancer (very rare)
  • Blockage of the urinary tract or bowel
  • Chronic pelvic pain, which may be debilitating

Rupture is a serious complication of endometriomas. Signs of a ruptured cyst include:

  • Pain with fever and vomiting
  • Sudden, severe abdominal pain
  • Faintness, dizziness, or weakness
  • Rapid breathing
  • Bleeding

If an ovarian endometrioma ruptures, you may experience severe, sudden abdominal and pelvic pain on the side where the cyst is located. If you have these symptoms or think you may have a ruptured cyst, seek medical attention immediately.

Risk of Infertility

Endometriosis is closely linked with infertility. As many as 50% of women with endometriosis and endometriomas have difficulty getting pregnant. Among women who are infertile, about 30% have endometriosis.

It is not known exactly how these conditions affect fertility, but experts think the increased risk may be due to:

  • A decrease in the "ovarian reserve," or the number of eggs available for fertilization: This may be due to the hormonal effects of the cysts.
  • Inflammation: It is believed that inflammation may interfere with the functions of the sperm and egg cells, making fertilization more difficult.
  • Fluid in the cysts: This may result in embryos that are not viable.


Your healthcare provider may consider a diagnosis of endometrioma if you have endometriosis and are experiencing symptoms or have unexplained fertility. A cyst can sometimes be felt during a pelvic exam.


Ultrasounds are good at identifying the presence of cysts, but they might not be able to determine the exact type of cyst you have.

There are several different types of ovarian cysts, including follicle cysts, corpus luteum cysts, dermoid cysts, and cystadenomas, most of which are more common than endometriomas.


A needle biopsy starts with an ultrasound to locate the exact location of the cyst. A thin, hollow needle and a syringe are inserted into the cyst to extract tissue and fluid.

The fluid and tissue samples are then examined under a microscope to determine if they contain endometrial cells, which is a key indicator of an endometrioma.

How Is an Endometrioma Treated?

Your healthcare provider will develop a treatment plan for endometriomas depending on several factors. These include your age, your symptoms, whether one or both ovaries are affected, and your plans for having children going forward.

Observation and Monitoring

Cysts that are not causing symptoms are usually not treated. Instead, your healthcare provider may take a watch-and-wait approach.

Birth Control Medications

Endometriosis responds to fluctuations in the hormones progesterone and estrogen.

For women who are not actively trying to conceive, hormonal forms of birth control, such as birth control pills, NuvaRing, or a hormonal birth control patch, can regulate hormone function, slow down cyst growth, and help reduce pain.


Surgery to remove cysts—called ovarian cystectomy—is recommended for women who have painful symptoms, large cysts, cysts that might indicate cancer, or infertility.

This procedure involves making small incisions (cuts) in the belly and inserting a laparoscope—a thin, long tube with a camera and light. This helps the healthcare provider see and remove the cyst.

In women who are planning to conceive, the risks and benefits of an ovarian cystectomy have to be weighed carefully. The procedure can potentially have a negative effect on ovarian function. This decreases the likelihood of conception, either naturally or with in vitro fertilization (IVF).

On the other hand, leaving endometriomas in place before undergoing treatment with IVF increases the risk of pelvic infection after a woman's eggs are extracted. They can also contaminate the culture in which the egg and sperm are joined.

Complementary Therapies

While this area hasn't been studied extensively for women who have endometrioma, some complementary or alternative therapies have been found to help some women with endometriosis.

These include acupuncture, Chinese medicine, vitamins, and dietary supplements.

Always talk to your healthcare provider before trying an alternative treatment.


In addition to medical approaches, you may find some relief from the symptoms and stress of an endometrioma by adjusting certain aspects of your lifestyle.


In recent years there has been a lot of interest in the role of inflammation in many diseases. Diet can affect inflammation.

Studies have shown that consuming a diet consisting largely of fresh vegetables, fresh fruit, and foods high in omega-3 fatty acids (such as salmon, halibut, walnuts, and flaxseeds) can significantly reduce the risk of endometriosis.

Eating red meat on a regular basis increases the risk.


Exercise may relieve the pain of endometrioma by encouraging healthy circulation, decreasing excessive estrogen production, relieving stress, and releasing pain-relieving endorphins in the brain.

Stress Management

The pain and potential infertility of an endometrioma can negatively affect all aspects of your life, including work, family, and relationships. Exercising, getting adequate sleep, and seeking individual talk therapy and/or a support group for women with endometriosis may all be effective ways to reduce stress.


Endometriomas are cysts that form on the ovaries when endometrial tissue grows on the ovaries. An endometrioma can form in women who have endometriosis.

Symptoms of an endometrioma include painful periods and heavy menstrual bleeding. While these cysts are rarely dangerous, they can cause fertility problems.

A Word From Verywell

Cysts associated with endometrioma can be painful and cause stress, especially for women who are planning to have children. Fortunately, there are many treatment options as well as lifestyle measures that can manage the pain and reduce the risk of complications.

Because endometriomas, as well as the surgery used to treat them in some cases, can significantly affect fertility, it's important to talk to your healthcare provider if you are trying to conceive.

Frequently Asked Questions

  • What kind of healthcare provider treats endometriomas?

    A gynecologist, a doctor who specializes in women's reproductive health, can diagnose and manage endometriomas.

  • How big do endometriomas get?

    Endometriomas don't usually grow larger than a few centimeters. However, it is possible for them to grow larger than that. Some can even become grapefruit-sized. Those larger than 4 cm are usually removed surgically.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Endometriosis Foundation of America. Sampson’s theory of retrograde menstruation.

  3. Brigham and Women's Hospital. Deep ovarian endometriosis (endometriomas).

  4. Shigesi N, Kvaskoff M, Kirtley S, et al. The association between endometriosis and autoimmune diseases: a systematic review and meta-analysis. Hum Reprod Update. 2019 Jul 1;25(4):486-503. doi: 10.1093/humupd/dmz014

  5. Endometriosis Foundation of America. Endometriomas and fertility.

  6. Office on Women's Health. Ovarian cysts.

  7. Cleveland Clinic. Needle biopsy.

  8. Brigham and Women's Hospital. Medical treatment for endometriosis.

  9. Buggio L, Barbara G, Facchin F, Frattaruolo MP, Aimi G, Berlanda N. Self-management and psychological-sexological interventions in patients with endometriosis: strategies, outcomes, and integration into clinical careInt J Womens Health. 2017;9:281-293. doi:10.2147/IJWH.S119724

By Lana Barhum
Lana Barhum has been a freelance medical writer since 2009. She shares advice on living well with chronic disease.