Hormonal health

Endometrioma: The 'Chocolate Cyst' Explained

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A chocolate cyst, or ovarian endometrioma, forms when endometriosis grows on an ovary and fills with old, dark blood. It is a sign of endometriosis, not a separate disease, and can affect pain and fertility. Some are monitored while others are removed, though surgery carries trade-offs for the ovary.

Last updated: July 2026

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What is a chocolate cyst?

A chocolate cyst is an ovarian cyst created by endometriosis. When endometriosis-like tissue takes hold on an ovary, it bleeds a little with each cycle, and that trapped blood darkens over time into a thick, brown fluid — the reason for the nickname 'chocolate cyst'. The medical term for it is an endometrioma. According to the 2022 ESHRE guideline, endometriomas are among the forms of endometriosis that imaging identifies reliably, which is why one is often first spotted on a pelvic ultrasound 1. Finding one usually means endometriosis is present elsewhere in the pelvis too, even if those areas do not show on a scan. So the cyst is often a visible clue to a larger, quieter condition.

What does an endometrioma mean for pain and fertility?

An endometrioma can affect both pain and fertility, though not always in obvious ways. Some cause significant period pain or pain with sex, while others are found by chance and cause few symptoms. Endometriosis affects roughly 1 in 10 women of reproductive age — around 10%, or about 190 million worldwide — and it is a common finding in people facing endometriosis and fertility challenges 2. An endometrioma itself can lower the number of eggs an ovary holds, and both the cyst and surgery to remove it may reduce ovarian reserve — the measure clinicians track with a blood test called AMH 3. This is why fertility plans so often shape decisions about treatment. Understanding that link early tends to make later choices clearer.

Does a chocolate cyst always need surgery?

Not every endometrioma needs to be removed. Small cysts that cause few symptoms are often monitored with periodic ultrasounds, and hormonal treatment can ease pain without an operation. According to ACOG, decisions about surgery weigh symptom severity, cyst size, fertility goals, and the risk of harming the ovary 4. Endometriosis is also a leading cause of chronic pelvic pain, present in as many as 1 in 3 of those evaluated for it, so relief matters 5. Removing a cyst can ease pain and confirm the diagnosis, but it can reduce ovarian reserve, so surgeons preserve as much healthy tissue as possible. For someone hoping to conceive that balance is delicate, and some explore treatment without surgery first.

How is an endometrioma monitored or treated?

Monitoring and treatment depend on symptoms, size, and life stage. A stable, symptom-light cyst may simply be watched with repeat imaging, while a painful or growing one may prompt hormonal treatment or surgery 1. Endometriomas typically appear during the reproductive years and often shrink after menopause as estrogen falls, so a cyst first found in the mid-forties may be handled differently than one found at 25 2. A new or rapidly changing cyst after menopause is watched more carefully, because the reasoning shifts once estrogen is low. Comparing an endometrioma with a simple ovarian cyst helps clarify why the approach differs. Age, in other words, is part of the diagnosis.

When a clinician helps with an endometrioma

An endometrioma finding is worth discussing in detail rather than worrying over alone. A gynecologist can explain what the cyst means for your symptoms and fertility, whether monitoring or treatment fits your goals, and when a fertility specialist should be involved. Bringing your questions about pregnancy timing and pain to that visit helps you weigh the trade-offs clearly. Gale can help you prepare for that conversation. Learning how surgeons compare excision and ablation can also help if an operation is ever on the table.

Common questions

Endometriomas are benign, not cancer; they are a form of endometriosis. A very small number of ovarian cancers have been linked to long-standing endometriosis, which is one reason persistent or changing cysts are monitored, but the overall risk stays low.

Endometriomas rarely disappear completely without treatment, though they can stay stable for a long time. Hormonal treatment may shrink them or ease symptoms. After menopause, when estrogen drops, some become smaller. Regular imaging helps track any change.

Many people with endometriomas conceive, though endometriosis can make it harder. The cyst and any surgery may affect ovarian reserve, so fertility goals are worth raising early. A fertility specialist can advise on timing and options if conceiving is proving difficult.

No. Removal is one option, not a rule. Small, quiet cysts are often monitored, and surgery is weighed against its effect on the ovary. The right choice depends on your symptoms, age, and pregnancy plans, decided with your gynecologist.

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When an ovarian cyst needs prompt attention

  • —Sudden, severe one-sided pelvic pain with nausea or vomiting warrants urgent, same-day evaluation for possible cyst rupture or ovarian torsion.
  • —Fever with worsening pelvic pain is a reason to seek prompt clinician review.
  • —A cyst that grows quickly or appears after menopause is a reason to see a gynecologist.
  • —Pain that keeps you from daily activities or sleep is a reason to have your treatment options reviewed.

This article is general health education, not medical advice. Whether an endometrioma should be monitored, treated, or removed is a decision to make with a gynecologist who knows your history.

References

  1. 1.Becker CM, et al. (ESHRE) (2022). ESHRE guideline: endometriosis. Human Reproduction Open. doi:10.1093/hropen/hoac009 ✓Supports that ovarian endometriomas are reliably seen on imaging, that an endometrioma signals endometriosis elsewhere, and that cystectomy can reduce ovarian reserve.
  2. 2.World Health Organization (2025). Endometriosis (fact sheet). World Health Organization (WHO). link ✓Supports the prevalence of roughly 10% (about 190 million), that endometriosis is common in those evaluated for infertility, and that it eases after menopause.
  3. 3.Practice Committee of the American Society for Reproductive Medicine (2020). Testing and interpreting measures of ovarian reserve: a committee opinion. Fertility and Sterility. doi:10.1016/j.fertnstert.2020.09.134 ✓Supports that anti-Mullerian hormone (AMH) is a blood marker of ovarian reserve used to gauge the pool of eggs an ovary holds.
  4. 4.American College of Obstetricians and Gynecologists (2010). Practice bulletin no. 114: management of endometriosis. Obstetrics & Gynecology. doi:10.1097/AOG.0b013e3181e8b073 ✓Supports that decisions about surgery for endometriosis weigh symptom severity, cyst size, fertility goals, and preservation of ovarian tissue.
  5. 5.American College of Obstetricians and Gynecologists (2020). Chronic Pelvic Pain: ACOG Practice Bulletin, Number 218. Obstetrics & Gynecology. doi:10.1097/AOG.0000000000003716 ✓Supports that endometriosis is a leading cause of chronic pelvic pain and is found in a substantial share of those evaluated for it.

5 sources, numbered by first appearance. General health information, not medical advice. AI-assisted editorial content — every citation independently verified. Editorial policy

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