Endometrioma (Chocolate Cyst)

A chocolate cyst, medically called an endometrioma, forms when tissue similar to the womb lining creates a cyst in an ovary. The name refers to the dark fluid inside, which resembles old blood. It is the ovarian form of endometriosis and is associated with pain, period symptoms or difficulty conceiving in some people, while others have no symptoms. Decisions about monitoring, medication or surgery depend on symptoms, cyst features, age and pregnancy plans. The information below offers a general overview and does not replace an individual diagnosis or treatment advice.

What is a chocolate cyst (endometrioma)?

Endometriosis means tissue similar to the womb lining occurring outside the womb. When this tissue is in an ovary, it responds to hormones and bleeds with each cycle. Blood builds up and forms an ovarian cyst. There may be one or several cysts, and their size varies.

A chocolate cyst differs from other ovarian cysts. Functional cysts, which develop with the menstrual cycle and often resolve on their own, and other ovarian cysts such as dermoid cysts are different structures with different assessment and treatment. People with a chocolate cyst may also have areas of endometriosis on the lining of the abdomen outside the ovaries.

What symptoms can an endometrioma cause?

A chocolate cyst may cause no symptoms and may be found during an ultrasound for another reason. When symptoms occur, they may include:

• Chronic pelvic pain during or outside periods
• Severe period pain (dysmenorrhoea)
• Pain during sex (dyspareunia)
• Difficulty conceiving
• Changes in menstrual pattern

These symptoms can also occur in other conditions, so they do not prove the presence of a chocolate cyst on their own. Symptom severity and cyst size may not correspond in every case.

How is an endometrioma diagnosed?

Assessment begins with the symptom history and a gynaecological examination. Transvaginal ultrasound is effective for diagnosing an ovarian endometrioma. The cyst's contents and wall may have a typical ultrasound appearance. Magnetic resonance imaging (MRI) is used if needed to clarify the diagnosis and extent of other areas of disease. Imaging may not show superficial endometriosis in every case; no imaging findings does not completely rule out the condition.

Tumour markers measured in blood tests, such as CA-125, can also rise because of endometriosis. They are not sufficient on their own to diagnose a chocolate cyst or rule out malignancy. The doctor undertakes further assessment if there are findings such as older age, rapid cyst growth or solid areas within it. Malignant transformation of a chocolate cyst is rare.

What treatment options are available for an endometrioma?

There is no single approach. Decisions depend on symptoms, cyst size and imaging features, age, ovarian reserve and pregnancy plans.

When is monitoring preferred?

Regular monitoring instead of surgery may be chosen for cysts with no symptoms and typical imaging features, particularly in people planning pregnancy or needing careful consideration of ovarian reserve. Cyst size, appearance and changes in symptoms are checked at intervals. The doctor decides the monitoring interval and duration for the individual.

What can medicines achieve?

Hormonal medicines are used to control endometriosis-related pain and period symptoms and reduce recurrence. They cannot be said to remove the cyst permanently. The aim is often symptom management and prevention of recurrence. The doctor decides which medicine to use and for how long according to pregnancy wishes, side effects and accompanying conditions. Current medical guidance states that hormone treatment before surgery does not improve the short-term outcome of surgery for pain.

When is surgery needed?

Surgery is considered when medication does not control pain sufficiently, cyst features require further assessment or there are other clinical reasons. When surgery for an endometrioma is planned, current medical guidance recommends removing the cyst with its wall (cystectomy) rather than draining and cauterising it, as this approach has been reported to reduce recurrence and pain. However, cystectomy can also affect ovarian tissue and reduce ovarian reserve. Possible effects and expectations about the chance of pregnancy should therefore be discussed in detail before surgery, particularly for people planning pregnancy. General surgical risks, such as bleeding, infection and effects on nearby organs, and the possibility of cyst recurrence also apply.

Can an endometrioma affect ovarian reserve and pregnancy chances?

A chocolate cyst may affect ovarian tissue and reserve, and surgery may reduce reserve further. The clinical effect on the chance of pregnancy varies between individuals and includes uncertainties. Current medical guidance does not recommend routine endometrioma surgery before IVF to increase live birth rates. Surgery may nevertheless be considered for reasons such as pain or cysts that make follicles difficult to access. If there is difficulty conceiving, a plan is drawn up by assessing ovarian reserve (AMH and antral follicle count) and partner factors together.

Can it recur after surgery, and how is follow-up arranged?

A chocolate cyst can recur after surgery. Long-term hormonal treatment may be recommended to reduce recurrence in people not planning pregnancy immediately afterwards. Hormonal suppression after surgery is not recommended solely to increase future pregnancy rates. Medicine choice and duration are decided with the doctor, and follow-up uses regular ultrasound.