What Is Ovarian Endometrioma

  • Simron JakhuBachelor of Science - BSc (Hons) Biomedical Science, University of Wolverhampton
  • Jenny Lee Master of Chemistry with medicinal Chemistry 2025


Endometriomas are cystic lesions found mainly in the ovaries. They stem from endometriosis and are the most common ovarian endometriosis manifestations. Endometriomas are sometimes referred to as ‘chocolate cysts’ as they are filled with dark brown endometrial fluid. The presence of endometriomas indicates a severe stage of endometriosis.1

Approximately 10% of women of reproductive age are affected by endometriosis. 17 to 44% of these women experience endometriomas, with 28% of them having bilateral endometriomas.1 Ovarian endometriomas account for 35% of all benign ovarian cysts.2

The risks of chronic pelvic pain, infertility, painful periods, painful intercourse, and pain when passing stool are all increased with endometriosis.1

Causes and risk factors

What is endometriosis?

Endometriosis is a neuro-inflammatory condition that affects 6% to 10% of women who are of reproductive age. It is also linked with crippling chronic pelvic pain. A definitive diagnosis of endometriosis is only considered when endometrial-like tissue (lesions) are found outside the uterus during surgery.

There are 3 subtypes of endometriosis: superficial peritoneal, which accounts for approximately 80% of endometriosis; ovarian (endometrioma);3 and deep, which accounts for approximately 20% of endometriosis.4

Risk factors of endometriosis

According to research, women who have endometriosis lesions have an increased risk of cardiovascular disease, melanoma, asthma, rheumatoid arthritis, breast cancer, and ovarian cancer.3

Risk factors for the development of endometriosis include early menarche (before 11-13 years of age, ie. early menstruation), heavy menstrual bleeding, late menopause, and short menstrual cycles.1

Endometriosis and ovarian endometriomas

As a subset of endometriosis, the pathophysiology of endometriomas is identical to that of endometriosis as a whole, i.e how they both develop is the same The ectopic endometrial tissue's hormonal response sets off the disease process pathway. This tissue, out of the uterus, reacts to the hormonal changes during a menstrual cycle, just like the intrauterine endometrium found in the uterus.

Inflammatory responses created by certain molecules lay the basis for producing new fibrous tissue formation and the growth of new blood vessels. Adhesions and pain that are frequently connected to this illness process are subsequently brought on by this snowball effect.1

Factors contributing to the development of ovarian endometrioma

While the development of endometriomas remains elusive, it is widely believed that endometriomas develop from retrograde menstruation, and other papers have suggested a possibility of endometriomas being associated with immune dysfunction, which can impede the removal of endometrial implants.5

In a usual menstrual cycle i.e. menstruation, the uterus lining is usually broken down during a period and expected to pass out of the cervix and through the vagina. However, in retrograde menstruation, the endometrial tissue travels backwards (retrogradely) through the fallopian tube into the pelvis during this menstrual cycle. This endometrial tissue then travels to different areas and plants itself, creating lesions. Some of these lesions may originate in the ovary and begin forming endometriomas.1


  • Painful periods
  • Heavy periods
  • Back pain
  • Pelvic pain
  • Bloating
  • Nausea/vomiting
  • Painful intercourse
  • Painful defecation
  • Painful urination
  • Frequently urinating1
  • Mid-cycle bleeding
  • Diarrhoea
  • Infertility4


Only a surgical diagnosis using direct visualisation and tissue samples can confirm the diagnosis of endometriosis and endometriomas. Biopsies must contain endometrial glands and stroma to confirm endometriosis's presence.1

Before a surgical diagnosis can occur a clinical history and physical examination of the patient is taken. During the physical examination, pelvic tenderness, tenderness in the area, and pain is generally found. Depending on the menstrual cycle, more pain and tenderness may occur during the examination.1 However, a physical examination alone is not enough to aid in an accurate diagnosis, so imaging techniques such as a transvaginal ultrasound (TVU) provide a more accurate assessment of where the lesions are.6

A transvaginal ultrasound is an imaging technique used to visualise cysts. Endometriomas generally appear to be simple cysts with a ground-glass appearance of the fluid in the cyst. They can appear to be multi-loculated with no more than four locules.1,6 An MRI is another imaging modality used. An MRI is more sensitive towards detecting a pelvic mass than a TVU. Endometriomas appear as round structures on an MRI.6

Laparoscopy is the gold standard in diagnosing endometriosis. Lesions appear black or blue but may be non-pigmented, red, or white. Laparoscopy is a very important procedure in endometriotic patients as it is both therapeutic and diagnostic.1


Infertility and chronic pain are the two main complications of endometriomas. Ovarian torsion is also a possible complication if the endometrioma measures 6 cm or larger. This would then require surgery, which could result in the loss of an ovary. Endometriomas have a small probability of developing into malignancy, and women with endometriosis are more likely to develop some forms of ovarian cancer, but the risk overall is low.1


Conservative management

Milder forms of endometriosis are treated by oral contraceptive pills, progestogens (intra-uterine device, oral pill, intramuscular) - this thickens the uterus lining, anti-progestogens, gonadotrophin-releasing hormone (GnRH) agonists (leuprolide), GnRH antagonists, and androgens (danazol).1,3 Although GnRH agonists have been shown to decrease the size of endometriomas, they do not make any difference in patients' pain, so they are not usually used in patients with endometriomas.1

Surgical intervention

Depending on the patient's symptoms and desire for future fertility, surgical therapy for endometriosis can take a variety of forms, from more conservative to more radical. A conservative approach would be to undergo a cystectomy via two methods – ablation and stripping. The ablation method of a cystectomy would destroy the lesions by a cautery (using heat from an electric current to destroy abnormal tissue) or laser, drain the endometrioma, and then remove the cystic capsule.1,6

The stripping technique would drain the endometria, pull apart the ovarian cortex and drain the endometria by grasping forceps, and then applying pressure to control the bleeding at the site of where the cyst is removed.6 Some patients choose to have a total hysterectomy combined with a bilateral salpingo-oophorectomy (removal of the uterus, fallopian tubes and ovaries) as a more conclusive course of treatment if their pain is extreme, and they do not want to become pregnant in the future.1

Fertility preservation

Oocyte cryopreservation and ovarian cortex cryopreservation are two possible ways to preserve fertility; however, further research is needed. Oocyte cryopreservation freezes gametes for future use.7 Ovarian cortex cryopreservation involves surgically removing ovarian tissue and freezing the cortical tissue.8

There are benefits and risks with both treatments:9

 Oocyte cryopreservationOvarian cortex cryopreservation
BenefitsSuccess rates are highAlternative for women who cannot or do not want to undergo ovarian stimulation (administration of hormones to stimulate egg growth)
 The laparoscopy can be avoidedAlternative for females in need of oophorectomy
 Risk of ovarian tissue damage is avoidedPotentially carried out during excisional (removing tissue) surgery for individuals who pose a risk
RisksMore research is necessary to determine the reproductive capacity of endometriosis patients’ folliclesThis is an experimental technology
 A large number of oocytes (immature eggs) need to be cryopreservedThere is potential for damage to occur to viable tissue
 There is a possibility that the quality of the oocyte and embryo may be impairedLaparoscopy carries risks


The prognosis is favourable for patients with endometriosis. Patients with endometriomas will have long-term complications as endometriomas signify the severity of the disease. The level of reoccurrence is high, so treatment may only be effective for a short period of time. Once entering menopause, women see an improvement in their symptoms because there is no longer any cyclical hormonal signalling.1

Patient education

Patients should receive education on the types of treatment available and what each treatment consists of, and any complications of having the condition.

As surgery is used to treat endometriomas, the patient must be educated on the procedure and the risks and benefits of undergoing this surgery. They should also be made aware that there is a high reoccurrence rate and that approximately 25% of women experience endometrioma reoccurrence.1

Patients should also be made aware that they may experience issues with chronic pelvic pain and fertility which is due to their underlying condition of endometriosis.1


What happens if you have an endometrioma?

You may be required to undergo surgery as part of treatment.1

Does an endometrioma need to be removed?

If the endometrioma is over 4 cm large, it would need to be removed.10

What is the difference between a cyst and an endometrioma?

Endometriomas are a specific type of cyst formed on the uterus when the endometrial tissue grows outside the uterus - the condition of endometriosis. They appear to be filled with brown fluid.1 Not all cysts are endometriomas.

Is an endometrioma cyst cancerous?

There is a small risk of endometriomas developing malignancy; however, they are not normally considered premalignant, so no screening nor staging workup is required.1


Endometriomas, often termed ‘chocolate cysts’, are manifestations of endometriosis. They indicate a severe stage of endometriosis and are associated with complications such as infertility. Symptoms of endometriomas include pelvic pain and painful periods.

Diagnosis is confirmed by surgery and with the use of imaging techniques. Management options include hormonal treatments to surgical intervention. Patient education is crucial as they need to know all this condition's risks, benefits, and complications. Patients should have an individual approach to treatment, taking into account their desires for fertility as well as their symptoms.


  1. Hoyle AT, Puckett Y. Endometrioma. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023. Available from: http://www.ncbi.nlm.nih.gov/books/NBK559230/
  2. Gałczyński K, Jóźwik M, Lewkowicz D, Semczuk-Sikora A, Semczuk A. Ovarian endometrioma – a possible finding in adolescent girls and young women: a mini-review. J Ovarian Res [Internet]. 2019 Nov 7;12(1):104. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6839067/
  3. Saunders PTK, Horne AW. Endometriosis: Etiology, pathobiology, and therapeutic prospects. Cell [Internet]. 2021 May 27;184(11):2807–24. Available from: https://www.sciencedirect.com/science/article/pii/S0092867421005766
  4. Ellis K, Munro D, Clarke J. Endometriosis is undervalued: a call to action. Frontiers in Global Women’s Health [Internet]. 2022 May 10;3. Available from: https://www.frontiersin.org/articles/10.3389/fgwh.2022.902371
  5. Jayaprakasan K, Becker C, Mittal M. The effect of surgery for endometriomas on fertility: scientific impact paper no. 55. BJOG [Internet]. 2017 Sep 25;125(6). Available from: https://obgyn.onlinelibrary.wiley.com/doi/10.1111/1471-0528.14834
  6. Cranney R, Condous G, Reid S. An update on the diagnosis, surgical management, and fertility outcomes for women with endometrioma. Acta Obstet Gynecol Scand [Internet]. 2017 Feb 10;96(6):633–43. Available from: https://obgyn.onlinelibrary.wiley.com/doi/10.1111/aogs.13114
  7. Somigliana E, Vigano P, Filippi F, Papaleo E, Benaglia L, Candiani M, et al. Fertility preservation in women with endometriosis: for all, for some, for none? Human Reproduction [Internet]. 2015 Apr 16;30(6):1280–6. Available from: https://academic.oup.com/humrep/article-lookup/doi/10.1093/humrep/dev078
  8. Harzif AK, Pratama G, Maidarti M, Prameswari N, Shadrina A, Mutia K, et al. Ovarian cortex freezing as a method of fertility preservation in endometriosis: A case report. Annals of Medicine and Surgery [Internet]. 2022 Feb;74:103222. Available from: https://www.sciencedirect.com/science/article/pii/S2049080121011729
  9. Llarena NC, Falcone T, Flyckt RL. Fertility preservation in women with endometriosis. Clin Med Insights Reprod Health [Internet]. 2019 Sep 3;13. Available from: http://journals.sagepub.com/doi/10.1177/117955811987338610. Ünlü C, Yıldırım G. Ovarian cystectomy in endometriomas: Combined approach. J Turk Ger Gynecol Assoc [Internet]. 2014 Sep 1;15(3):177–89. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4195329/
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Simron Jakhu

Bachelor of Science - BSc (Hons) Biomedical Science, University of Wolverhampton

Simron is a first-class biomedical science graduate. She has experience in different areas such as data analysis, laboratory work, and academic writing. Her research project investigated the quantification of immunosuppressive proteins in glioblastoma multiforme by ELISA.

She is someone who enjoys learning and expanding her knowledge, especially in the areas of health and science. By using her experience and knowledge to write articles, Simron hopes they can be helpful to the general public.

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