Endometriotic Cysts – Causes, Symptoms, Treatment

Endometriotic Cysts/Endometrioma is the presence of endometrial tissue in and sometimes on the ovary. It is the most common form of endometriosis. Endometrioma is found in 17–44% of patients with endometriosis.[rx] Endometriomas are typically an advanced form of endometriosis, around stage three or four.[rx] More broadly, endometriosis is the presence of endometrial tissue located outside the uterus. The presence of endometriosis can result in the formation of scar tissue, adhesions, and an inflammatory reaction. It usually is a benign growth. An endometrioma is most often found in the ovary.[rx] This ovarian endometriosis forms dark, fluid-filled cysts.[rx] These fluid-filled sacs can vary greatly in size and are known as endometriomas, also called chocolate cysts. The fluid inside the cysts is thick, dark, old blood, giving it a chocolate-like appearance. It can also develop in the cul-de-sac (the space behind the uterus), the surface of the uterus, and between the vagina and rectum.[rx]

Endometriomas, also known as chocolate cysts or endometriotic cysts or ovarian endometrioma, or endometrioid cysts is  a localized form of endometriosis and are usually within the ovary. They are readily diagnosed on ultrasound, with most demonstrating classical radiographic features.

Endometrioma is a common, estrogen-dependent, inflammatory, gynecologic disease process in which normal endometrial tissue is abnormally present outside of the uterine cavity. Endometriomas are cystic lesions that stem from endometriosis. Endometriomas are most commonly found in the ovaries. Affecting approximately 10% of reproductive-aged women, endometriosis is a common cause of chronic pain, dyspareunia, dysmenorrhea, and infertility. Most commonly, endometriosis is found within the pelvis, specifically on the ovaries.


There are 4 stages of endometriosis described by the American Society for Reproductive Medicine. The stages are minimal, mild, moderate, and severe. Staging is completed surgically, most commonly via laparoscopy.

  • Stage I (minimal) – Small solitary lesions without significant adhesions
  • Stage II (mild) – Superficial lesions < 5 cm, without significant adhesions
  • Stage III (moderate) – Multiple deep implants, small endometriomas unilaterally or bilaterally on the ovaries, and thin adhesions
  • Stage IV (severe) – Multiple deep implants, large endometriomas unilaterally or bilaterally on the ovaries, thick adhesions

As can be seen by these descriptions, if an endometrioma is present, the patient is already a stage 3 or 4. Most patients are found to have stage 1 or 2 endometriosis. However, staging does not always coincide with the severity of symptoms.

Causes of Endometriotic Cysts

Endometriomas are most commonly thought to be caused when seeding of ectopic endometrial tissue, most often present on the ovary, bleeds, causing a hematoma. This commonly occurs with the natural menstrual cycle of a woman, due to the fact that the ectopic endometrial tissue is still hormonally active. Therefore, this tissue will naturally shed with the withdrawal of progesterone after the breakdown of the corpus luteum..

This theory of retrograde menstruation is likely a contributing factor to the development of endometriosis. However, most people in the medical community feel that it is more of a multifactorial development. For instance, it is difficult to believe this theory in women who have distant endometriosis lesions, or pre-pubescent females with endometriosis. Therefore, other theories that have been suggested include the theory of metaplasia.

There is also limited data to suggest specific risk factors for endometriomas alone. However, there are known risk factors for the development of endometriosis in general.

These include:

  • Nulliparity
  • Early menarche (typically before 11-13 years old)
  • Late menopause, short menstrual cycles (less than 27 days)
  • Heavy menstrual bleeding
  • Mullerian anomalies
  • Height greater than 68 inches
  • Low body mass index (BMI)
  • Consumption of high amounts of trans unsaturated fat
  • Exposure to diethylstilbestrol in utero
  • such as infertility, chronic pelvic pain, dyschezia, dyspareunia, and dysmenorrhea.
  • certain types of ovarian cancer. The overall risk of ovarian cancer remains low.
  • endometrioid ovarian cancer.

Symptoms of Endometriotic Cysts

  • Pelvic pain
  • Heavy menses
  • Painful menses
  • Back pain
  • Painful sexual intercourse (dyspareunia)
  • Painful defecation (dyschezia)
  • Painful urination (dysuria)
  • Urinary frequency
  • Nausea/vomiting
  • Bloating
  • Symptomatic endometriosis is frequently nulliparous in females of reproductive age with a chief complaint of heavy or painful menses. Their periods will often last longer than 7 days. They may complain of chronic pelvic pain, pain with sexual intercourse, or defecation.
  •  If an ovarian endometrioma ruptures, the thick endometrial fluid can spill throughout the abdomen and cause significant pain and inflammation.
  • The main symptom of endometriosis is a pain in the abdomen (lower belly). This often arises when women have their menstrual period, or during or after sex. The severity of pain may vary, sometimes radiating into the lower belly, back and legs. It is often described as “cramp-like” pain and might be accompanied by nausea, vomiting, and diarrhea.

Diagnosis of Endometriotic Cysts

The only way to confirm the diagnosis of endometriosis, including endometriomas, is to surgically diagnose it with direct visualization and tissue samples. In order to confirm the presence of endometriosis in the tissue, the biopsy must contain both endometrial glands and stroma.


Their periods are typically regular in nature, though they may have shorter menstrual cycles (less than 27 days). The onset of pain for these patients is typically 2-3 days prior to the onset of their menses, and the pain typically begins to resolve a couple of days after their menses has started. 


Endometriosis, including those with endometriomas, typically has minimal findings on physical exam. Endometriomas, if large enough, could be felt on a bimanual exam. You will often find generalized pelvic tenderness or tenderness to the affected area. The patient will often have more pain if the exam is completed just before the onset of her menses in comparison to if it was done just after her menses completed.

However, if a patient presents after the rupturing of an endometrioma, the patient could have an acute abdomen upon evaluation. These findings include peritoneal signs, which commonly present as abdominal rigidity, rebound pain, and involuntary guarding.


However, there are a limited number of tests that can be used as a tool to assist with the diagnosis.

  • Laboratory evaluations –  that can be considered for these patients include a complete blood count (CBC), cancer antigen (CA)-125, CCR1, urinalysis, and sexually transmitted infection (STI) testing. The CBC can help guide the concern for infection and anemia. If there is an elevated white blood cell count, the suspicion for an infectious cause of the patient’s pelvic pain would be higher.
  • The hemoglobin – can also help guide you to the level of blood loss, as these patients typically have heavier periods and may be anemic as a result. CA-125 can be elevated in women with endometriosis. However, this is a non-specific marker, and it is not routinely ordered.
  • CCR1 is a new lab marker – that has been shown to be higher in peripheral blood leukocytes of women with endometriosis. This is not yet commonly ordered as a standard practice but could be a test to consider in these patients while completing their work-up. It is also important to complete urinalysis to rule out a UTI from the differential diagnosis, as well as STD testing such as cervical cultures for gonorrhea and chlamydia in order to rule out these infections.
  • Transvaginal ultrasound – is commonly ordered for these patients to determine if there is a cause for their pelvic pain that can be visualized. Superficial implants of endometriosis cannot be seen on ultrasound, nor any other imaging modality. However, ultrasound is often where endometriomas are found.
  • CT scan – exposes the patient to radiation, and although it may identify a pelvic mass, the characteristics of the mass on CT scan do provide good clues as to the type of mass it is. Therefore, a CT scan is not the ideal imaging modality in these patients.
  • Laparoscopy –  endometriosis lesions will typically appear blue or black in color. However, they can be seen as red, white, or non-pigmented lesions. At this time, the severity of the disease can also be evaluated. If there are significant adhesions, peritoneal defects, or endometriomas present, this is indicative of more severe disease. The visualized lesions can then be biopsied and evaluated by pathology for endometrial glands and stroma.  Laparoscopy is an important procedure in patients with endometriosis, because although it is diagnostic, it is also therapeutic, especially in cases with endometriomas. This is an important part of treatment for these patients with refractory endometriosis or patients with symptomatic endometriomas.
  • Ultrasound – The appearance of endometriomas can be quite variable. The classical example is a unilocular cyst with acoustic enhancement with diffuse homogeneous ground-glass echoes as a result of the hemorrhagic debris. This appearance occurs in 50% of cases.
  • Less typical features include:
  • multiple locules (~85% will have <5 locules)
  • hyperechoic wall foci (present in 35%)
  • cystic-solid lesion (~15%) or purely solid lesion (1%)
  • anechoic cysts (rare; 2%)

Magnetic resonance imaging (MRI) – and computed tomography (CT). MRI has actually been shown to have a higher sensitivity for detecting a pelvic mass than ultrasonography. However, due to the cost of an MRI, the benefit does not outweigh the financial burden, and thus ultrasound is more commonly used. Like ultrasound, MRI is limited in detecting diffuse pelvic endometriosis, and may only be beneficial for finding endometriomas.

Signal characteristics vary according to the age of any complicating hemorrhage


  • typically, lesions appear hyperintense while acute hemorrhage occasionally appears hypointense
  • endometriomas with high T1 signal characteristically do not show loss of signal on T1 fat-suppressed sequence, which is important for differentiating it from mature cystic teratoma of the ovary.


  • typically hypointense owing to the presence of deoxyhemoglobin and methemoglobin (shading sign), which is very suggestive of endometrioma.
  • T2 dark spot sign is specific for chronic hemorrhage and is helpful in diagnosing endometriomas 9
  • old hemorrhage occasionally appears hyperintense


  • variable restricted diffusion


  • may have wall enhancement
  • the presence of an enhancing mural nodule is suggestive of malignant transformation

Treatment of Endometriotic Cysts

Treatment of endometriosis mainly consists of hormonal medications or surgical treatment.

  • Milder forms of endometriosis –  can be treated with oral contraceptive pills, various forms of progesterone (oral pill, intrauterine device), gonadotropin-releasing hormone (GnRH) agonists (such as leuprolide), or androgens (such as danazol.
  • GnRH agonists – have been shown to decrease the size of endometriomas. However, patients have not reported any difference in their pain. Therefore, this option is typically abandoned for patients with endometriomas.
  • Nonsteroidal anti-inflammatory drugs (NSAIDs) – are frequently used first in patients with pelvic pain, particularly if the diagnosis of endometriosis has not been definitively (excision and biopsy) established. The goal of directed medical treatment is to achieve an anovulatory state. Typically, this is achieved initially using hormonal contraception. This can also be accomplished with progestational agents (i.e., medroxyprogesterone acetate), danazol, gestrinone, or gonadotropin-releasing hormone agonists (GnRH), as well as other less well-known agents. These agents are generally used in oral contraceptives and NSAIDs are ineffective. GnRH can be combined with estrogen and progestogen (add-back therapy) without loss of efficacy but with fewer hypoestrogenic symptoms. These medications are often ineffective in treating endometriomas and any relief is short-lived while taking the medications. Therapy with these agents has a large number of sometimes permanent side effects, such as hot flushes, loss of bone mass, deepening of the voice, weight gain, and facial hair growth.[rx]
  • AMH (anti-mullerian hormone) – Women have been shown to have a lower AMH (anti-mullerian hormone) level after cystectomy, which is a hormone used by fertility specialists to measure ovarian reserve. There has also been a reported 2-3% of patients having ovarian failure after resection of bilateral endometriomas.  After surgery, some providers place patients on medical therapy to attempt to prevent a recurrence. There have been studies that show a 6-month course of oral contraceptive pills helps to prevent a recurrence. However, this treatment option again depends on the patient and whether or not they are trying to conceive.

The following options are available for conservative surgical treatment of ovarian endometrioma. These methods, the combined technique, and the two- or three-step approach are described below.


  • After mobilization of the ovary and drainage of the cyst, make an incision to reveal the cleavage plane; this may be either on the edge of the cyst opening or a central incision, which divides the cyst into two halves. With both approaches, the incision should be away from the blood vessels in the hilum/Meso-ovarium. The use of a cold cut at the edge of the cyst opening may assist in identifying the cleavage plane.
  • To aid dissection and identification of the cyst wall, saline or diluted synthetic vasopressin solution (0.1–1 unit/ml) may be injected under the cyst capsule. The diluted synthetic vasopressin injection has the additional advantage of reduced bleeding during cyst removal. Synthetic vasopressin is not available in all countries and, although rare, may cause intraoperative cardiovascular complications including bradycardia and hypertension.
  • In some cases, a cleavage plane may not easily be identified after the ovarian incision. In such cases, it may be better to take a small part of the cyst wall for histological diagnosis and then use an ablation method, rather than risking damage to the ovary from persistent attempts to perform a cystectomy.
  • Once the cleavage plane is identified, use gentle traction and counter-traction with appropriate instruments to dissect the cyst capsule from the ovarian parenchyma. Traction and counter-traction may be effective during the initial part of the dissection. Avoid the use of excessive force to separate a highly adherent cyst from the ovary, as this will likely cause tearing of the ovarian tissue, excessive bleeding, plus the need for coagulation or diathermy, and thus further damage the normal ovarian tissue.
  • Careful identification of the cleavage plane and precise spot bipolar coagulation is the key to achieve hemostasis, to prevent unnecessary damage to healthy tissue, and to avoid blind or excessive diathermy.
  • Ensure final hemostasis after complete removal of the cyst capsule. Bipolar coagulation, suturing or intraovarian hemostatic sealant agents may also be used for this purpose. It is important to avoid damaging the major blood supply at the hilum coming in from the ovarian and infundibulopelvic ligaments at this stage.
  • After the removal of large endometriomas, it may be necessary to reconstruct the ovary and achieve hemostasis with monofilament sutures. For small endometriomas, suturing is often not required as the ovarian opening usually approximates spontaneously. If a suture is used, it should ideally be placed inside the ovary, as the exposed suture may be prone to adhesion formation.
  • Small cyst walls may be divided and retrieved directly through a port. Large cyst walls can be removed in a specimen retrieval bag. The posterior colpotomy is very rarely used for the retrieval of endometriomas.

Laser ablation

  • Ablate the entire inner surface of the cyst wall using the laser beam. Power settings of 30–55 W for the CO2 laser beam and 6–10 W for CO2 fiber (based on animal data) are usually used. The laser should be on the ablate function to widen the beam (e.g. ‘defocus’ or ‘surgical’). The laser should be applied in such a mode that it can ablate the tissue while preserving the underlying healthy tissue.
  • Aim to vaporize the endometriotic cyst lining only until haemosiderin pigment-stained tissue is no longer visible (until the color changes from reddish to yellow-white). The entire depth of the cyst capsule does not need vaporization, as endometriotic tissue is present only superficially.
  • Use intermittent irrigation to maintain good visibility and to remove carbon debris.
  • Ensure the border of the cyst opening is completely vaporized.

Plasma energy ablation

  • Ablate the entire inner surface of the cyst wall using plasma energy in coagulation mode set at 10 to 40, at a distance averaging 5 mm from the tip of the handpiece [, ].
  • Aim to vaporize the endometriotic cyst lining only until haemosiderin pigment-stained tissue is no longer visible (until the color changes from reddish to yellow-white). The entire depth of the cyst capsule does not need vaporization, as endometriotic tissue is present only superficially.
  • Take care to treat all areas and to ablate the edges of the invagination site.
  • When cyst eversion is not feasible, expose the cyst interior progressively to apply the plasma at an angle perpendicular to the inner surface of the cyst.


Electrosurgery is widely used for the treatment of ovarian endometrioma. Coagulation modes with different techniques and electrodes lead to different voltage levels, including modulation of high-frequency (HF) current with soft coagulation, forced coagulation, or spray coagulation. These various application modes result in different effects on the target tissue and cause different degrees of tissue damage[rx].

  • Coagulate the cyst lining systematically using bipolar forceps. The power setting depends on the generator and the type of forceps used, but a 25–40 W setting is frequently used. It is advisable to start at a lower power setting and adjust it depending on the effectiveness of coagulation achieved. The key point is to use very short coagulation times to minimize ovarian tissue damage, as the depth of the destruction can be difficult to judge.
  • Monopolar energy may be used in selected areas where there is fibrotic endometriotic tissue located at the hilum. A power setting of 15–20 W is frequently used.
  • Tissue damage tends to be deeper than with laser and plasma energy ablation; hence, the ovary should be cooled frequently with irrigation fluid.

Combined technique

A combined technique using both excision and ablation can be used to prevent excessive bleeding and ovarian tissue removal/damage from the ovarian hilum, particularly for larger endometriomas.

  • Open and drain the cyst followed by identification of the cleavage plane, as described above.
  • Strip 80–90% of the cyst wall and perform a partial cystectomy, as described above, up to the ovarian hilum. Laser, plasma energy, or bipolar can then be applied to treat the remaining endometriotic tissue (10–20%).
  • Suturing of the ovary may be considered to restore anatomy.

Two- or three-step approach for large endometriomas

For large endometriomas, a two- or three-step procedure can be considered.

  • The first step involves opening and draining the endometrioma as described in the initial stage section.
  • Inspect the cyst cavity and take a biopsy.
  • Following this initial step, administer a GnRH agonist (GnRHa) therapy for 3 months, during which time the thickness of the cyst wall significantly decreases, with atrophy and reduction in stromal vascularisation of the cyst [].
  • Complete the surgery with a second laparoscopy in the form of either cystectomy, CO2 vaporization, bipolar diathermy, or plasma ablation of the cyst wall lining.

Although women have to undergo two invasive procedures, the potential benefit is that this may facilitate the management of larger ovarian endometriomas, reduce recurrence rates and limit the decrease in ovarian reserve.


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