An endometrioma is a cyst that forms when tissue similar to the lining of the uterus grows inside an ovary and bleeds with each menstrual cycle. The trapped blood turns dark and thick over time, which is why it is sometimes called a chocolate cyst. Symptoms can include pelvic pain, painful periods, and pain during sex, and treatment ranges from pain relief and hormone therapy to surgery, depending on size, symptoms, and whether you want to have children.
What Is An Endometrioma Cyst Symptoms Treatment?
Endometriomas are a specific feature of endometriosis, a condition where tissue resembling the uterine lining grows outside the uterus. When that tissue settles on or inside an ovary and repeatedly bleeds, the blood has nowhere to drain. It collects in a pocket and forms a cyst.
Over months, the old blood becomes thick and dark brown. That color is the reason for the “chocolate cyst” nickname. Endometriomas are sometimes called endometriotic cysts. They are different from ordinary ovarian cysts, which usually form from normal ovulation and often resolve on their own.
An endometrioma does not resolve on its own in the way a simple functional cyst does. It is a sign of endometriosis, and it needs proper evaluation. Many people with an endometrioma also have endometriosis elsewhere in the pelvis.
How Is an Endometrioma Different From a Regular Ovarian Cyst?
Most ovarian cysts are functional. They form during a normal menstrual cycle, fill with clear fluid, and often shrink within a few cycles. An endometrioma is not functional. It is filled with old blood and lined with endometriosis-like tissue.
The distinction matters because the two are managed differently. A simple fluid-filled cyst is often watched and rechecked with ultrasound. An endometrioma is usually monitored more closely and may need treatment, especially if it is large or causing symptoms.
On ultrasound, an endometrioma has a fairly characteristic appearance: a cyst with a uniform, low-level “ground glass” pattern of internal echoes. Experienced sonographers often recognize it from this pattern. Imaging is not always definitive, though, and other types of cysts can occasionally look similar.
| Feature | Functional cyst | Endometrioma |
|---|---|---|
| Cause | Normal ovulation cycle | Endometriosis tissue in the ovary |
| Contents | Clear fluid | Thick, dark old blood |
| Typical course | Often resolves on its own | Usually persists |
| Ultrasound look | Simple, clear | Ground glass internal pattern |
What Are the Symptoms of an Endometrioma?
Some endometriomas cause no symptoms at all and are found during an imaging test done for another reason. When symptoms do appear, they tend to reflect the underlying endometriosis as much as the cyst itself.
Common symptoms include:
- Pelvic or lower belly pain, sometimes constant and sometimes tied to your period
- Painful menstrual cramps that may get worse over time
- Pain during or after sex, particularly with deep penetration
- Pain with bowel movements or urination, especially around your period
- Heavy or irregular bleeding
- Difficulty getting pregnant
It is worth being clear about one thing: the size of an endometrioma does not reliably predict how much pain it causes. A small cyst can be very painful, and a large one can be silent. Pain comes from inflammation, scarring, and where the endometriosis tissue sits, not simply from the cyst’s dimensions.
Severe sudden pelvic pain, especially with nausea, vomiting, or fever, is a reason to seek urgent care. In rare cases an endometrioma can rupture or twist the ovary, and those are medical emergencies.
What Causes an Endometrioma?
Endometriomas form as part of endometriosis, but why endometriosis develops in the first place is still not fully understood. The most widely discussed explanation is retrograde menstruation, where menstrual blood flows backward through the fallopian tubes into the pelvis. Most women have some backward flow, yet only some develop endometriosis, so that process alone does not explain it.
Researchers believe several factors likely combine: genetics, immune system differences, hormonal influences, and how certain cells behave outside the uterus. Endometriosis tends to run in families, which points to a genetic component. The exact mechanism is still an active area of research, and no single cause has been confirmed.
Endometriosis is relatively common. It affects a meaningful share of women of reproductive age, though estimates vary widely because diagnosis is often delayed. One reason for delay is that pain is sometimes dismissed as normal period pain.
How Is an Endometrioma Diagnosed?
Diagnosis usually starts with your history and a pelvic exam, followed by imaging. Transvaginal ultrasound is typically the first imaging test and is good at identifying the ground glass appearance of an endometrioma. MRI can be used when the picture is unclear or before surgery.
A blood test called CA-125 is sometimes checked, but it is not a reliable diagnostic test for endometriosis. CA-125 can be elevated in endometriosis, but it can also be elevated for many other reasons, and a normal result does not rule anything out. It is used more to help monitor known disease than to diagnose it.
The only way to confirm endometriosis definitively is through surgery, usually laparoscopy, where a surgeon can see the tissue directly and take a biopsy. That said, a classic endometrioma seen on ultrasound is often treated as endometriosis without surgery, because the imaging findings are fairly characteristic. The choice to confirm with surgery depends on your situation and symptoms.
How Is an Endometrioma Treated?
Treatment depends on several things: the size of the cyst, your symptoms, your age, and whether you want to become pregnant. There is no single approach that fits everyone, and the evidence for some options is stronger than for others.
Watchful waiting
Small endometriomas that cause few or no symptoms are sometimes monitored with repeat ultrasound rather than treated right away. This is a reasonable option for some people, particularly if fertility is not an immediate concern. Regular follow-up matters because these cysts can grow.
Pain relief
Over-the-counter pain relievers such as nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used for endometriosis pain. They can ease symptoms but do not shrink the cyst or stop the disease from progressing. A clinician can advise on what is appropriate for you.
Hormone therapy
Hormonal treatments — including combined hormonal contraceptives, progestins, and other options that suppress ovarian activity — are widely used to reduce endometriosis pain. They work by lowering the hormonal drive that makes endometriosis tissue bleed and grow. These treatments can ease symptoms, but they do not reliably make an existing endometrioma disappear, and symptoms often return after stopping. The evidence supports their use for pain control, not as a cure.
Surgery
Surgery is generally considered when an endometrioma is large, causing significant symptoms, or when the diagnosis is uncertain. The usual procedure is laparoscopic removal of the cyst, called cystectomy. Surgery can relieve pain and confirm the diagnosis, but it carries risks, including a chance of reduced ovarian reserve because some healthy ovarian tissue can be removed along with the cyst. For anyone planning pregnancy, this is an important conversation to have with a specialist before surgery.
There is genuine debate among specialists about the ideal size threshold for surgery and about how best to preserve ovarian function. That uncertainty is real, not a gap in your understanding. A gynecologist or a reproductive endocrinologist can help weigh the trade-offs for your specific case.
Fertility treatment
Endometriomas and endometriosis can affect fertility. If you are trying to conceive, treatment planning usually involves both a gynecologist and a fertility specialist. The right path — surgery, assisted reproduction, or a combination — depends on your age, ovarian reserve, and the size and location of the cyst.
Can an Endometrioma Affect Fertility?
Yes, endometriomas and the endometriosis around them can affect fertility. The cyst itself can damage ovarian tissue, and endometriosis is associated with inflammation and scarring in the pelvis that can interfere with the normal process of ovulation and fertilization.
That does not mean pregnancy is impossible. Many people with endometriosis conceive, sometimes on their own and sometimes with help. What it does mean is that if you are trying to conceive and have a known endometrioma, it is worth discussing timing and options with a specialist rather than waiting indefinitely. The evidence on how much a given cyst affects a given person’s fertility is not precise, so individual assessment matters.
What Should You Do If You Think You Have One?
Start by tracking your symptoms — when pain occurs, how severe it is, and how it relates to your cycle. Bring that record to a clinician. Pain that disrupts your life, pain during sex, or trouble getting pregnant are all reasons to seek evaluation rather than accept it as normal.
Ask for imaging if it has not been done. A transvaginal ultrasound is a reasonable first step. If an endometrioma is found, ask about its size, whether monitoring or treatment makes sense, and how it might affect fertility if that is a concern for you.
Endometriosis is often under-recognized, and getting a clear answer can take time. That is a reality of the condition, not a reflection of whether your symptoms are real.
Frequently Asked Questions
Can an endometrioma go away on its own?
An endometrioma usually does not resolve on its own the way a simple functional cyst can. Some may shrink or stabilize over time, but they generally persist and need monitoring.
Is an endometrioma the same as endometriosis?
An endometrioma is a specific manifestation of endometriosis located in the ovary. Having one means you have endometriosis, though endometriosis can also affect other areas of the pelvis.
Does an endometrioma need surgery?
Not always. Small cysts with mild symptoms are sometimes monitored, while surgery is generally considered for large cysts, significant pain, or uncertain diagnosis. The decision depends on your symptoms and fertility plans.
Can I get pregnant with an endometrioma?
Many people with endometriomas do conceive, sometimes naturally and sometimes with fertility treatment. Because the cyst and surrounding endometriosis can affect fertility, it is worth talking with a specialist if you are trying to conceive.
