Definition
Endometrioma is an ovarian cyst caused by the presence of ectopic endometrial tissue within the ovary. It is a manifestation of ovarian endometriosis, characterized by the collection of dense, degraded hemorrhagic material, which is why it is often referred to as a "chocolate cyst."
Etiology
The most widely accepted pathogenetic hypothesis is that of retrograde menstruation, according to which during menstrual flow a portion of endometrial tissue flows backward through the fallopian tubes and implants in ectopic locations, including the ovarian surface.
Other theories suggest that the endometrioma represents the outcome of progressive invagination and duplication of the ovarian cortex, secondary to repeated bleeding from superficial endometriosis foci.
Due to its location beneath the ovarian surface, the main clinical implication of endometrioma is the potential reduction of ovarian reserve — the available follicular pool at a given time. This compromise may be more pronounced when surgical treatment becomes necessary.
Symptoms
The main symptoms associated with the presence of an endometrioma are:
- Infertility
- Chronic pelvic pain
- Dysmenorrhea
- Dyspareunia
Diagnosis
Transvaginal ultrasound represents the first-line examination, with a sensitivity of approximately 80% and a specificity of approximately 90%. The typical endometrioma appears as a unilocular cystic formation, round or ovoid in shape, often referred to as a "chocolate cyst" due to the dense hemorrhagic content resulting from cyclic accumulation of degraded blood during menstrual cycles. It generally presents thickened but regular walls. In cases of bilateral involvement, the ovaries may be prolapsed and adherent posterior to the uterus, in the pouch of Douglas, configuring a picture suggestive of advanced pelvic endometriosis, with possible tubal and bowel involvement. Although the ultrasound characteristics of ovarian endometrioma often allow an accurate diagnosis, the findings may be less typical when the cyst is identified in postmenopausal women, raising differential diagnostic concerns with a borderline or malignant neoplasm.
Initial evaluation, key symptoms, and physical examination — adapted from As-Sanie et al., JAMA 2025
Key symptoms that should raise suspicion for endometriosis include progressive dysmenorrhea (worsening over time, unlike primary dysmenorrhea), non-menstrual pelvic pain, deep dyspareunia, and infertility. Ninety percent of patients with endometriosis report at least one pelvic pain symptom. Other important symptoms include cyclic dyschezia (pain during defecation during menstruation, 27%), cyclic dysuria, and cyclic bowel or bladder symptoms. Warning signs for deep endometriosis include hematochezia, hematuria, intestinal obstruction, or hydroureteronephrosis (present in <1% of cases). On physical examination, tender nodules at the uterosacral ligaments, rectovaginal septum nodules, or adnexal masses are suggestive of endometriosis.
Ref.: [1][3][4]
- Assess for current or past trauma before examination
- Build trust and validate the pain reported by the patient
- Ensure the presence of a chaperone and adequate draping during pelvic examination
- Inform the patient that she may refuse any part of the examination or stop it at any time
- Dysmenorrhea interfering with daily activities and quality of life
- Non-menstrual pelvic pain
- Deep dyspareunia (pain with deep vaginal penetration)
- Dysuria and/or hematuria, worse during menstruation
- Dyschezia and/or hematochezia, worse during menstruation
- Abdominal wall pain, worsened by menstruation
- Pneumothorax, hemoptysis, right shoulder pain during menstruation
| Position / Exam | Seated — Back | Supine — Abdomen | Lithotomy — Digital | Bimanual | Speculum |
|---|---|---|---|---|---|
| Findings suggestive of endometriosis | |||||
| — | — | Tender umbilical nodule; tender abdominal wall nodule (frequently at cesarean section scar) | Nodularity or tenderness of the posterior cul-de-sac (deep endometriosis at uterosacral ligaments, rectovaginal septum, and/or rectosigmoid colon) | Nodularity and/or tenderness of the posterior cul-de-sac (deep endometriosis); reduced uterine mobility with tenderness; adnexal mass (endometrioma) | Tender blue-gray nodule in the posterior vaginal fornix (vaginal endometriosis) |
| Findings suggestive of overlapping conditions or other gynecologic pathology | |||||
| Paravertebral, coccygeal, or sacroiliac joint tenderness (possible musculoskeletal or rheumatologic origin) | Neuropathic pain around surgical scars; abdominal wall trigger points (myofascial pain) | Vulvar tenderness on cotton swab test (vestibulodynia); pelvic floor tenderness (myalgia); bladder tenderness (bladder pain syndrome / interstitial cystitis) | — | Enlarged uterus (uterine fibroids, adenomyosis); adnexal mass (non-endometrioma) | Vaginal atrophy, lichen planus (dyspareunia) |
Source: As-Sanie S et al. Endometriosis. JAMA. 2025;334(1):64-78. [Ref. 1]
The presence of an endometrioma with typical characteristics nonetheless requires careful clinical and imaging follow-up, with potential surgical indication in cases of suspected evolution.
Treatment
In the majority of cases, treatment is medical.
First-line medications are combined estrogen-progestins, used both in less severe forms for pain control and after surgery in more complex cases, with the aim of reducing the risk of recurrence.
Laparoscopic surgical treatment is associated with a potential reduction of ovarian reserve and should be reserved for patients with a suspicious cyst, in the event of significant size increase, or in patients unresponsive to medical therapy. The main techniques include cyst wall enucleation — complete excision of the cyst — and fenestration followed by ablation or coagulation.
The clinical consequences of surgical damage are generally more limited in the presence of a unilateral endometrioma, since the contralateral ovary maintains its function. However, these consequences may be more significant in cases of bilateral endometriomas. In these situations, it may be appropriate to evaluate fertility preservation strategies, such as oocyte cryopreservation, embryo cryopreservation, or ovarian tissue cryopreservation.
Frequently Asked Questions
Endometriosis is a chronic estrogen-dependent inflammatory disease characterized by the presence of endometrial-like tissue outside the uterine cavity. Endometrioma, on the other hand, represents a specific ovarian manifestation of the disease and consists of an ovarian pseudocyst lined by endometrial glands and stroma. Clinically, endometriosis encompasses superficial peritoneal, deep, ovarian, and extrapelvic forms, while endometrioma identifies ovarian involvement and is often associated with more extensive forms of disease.
Ref.: [1, 2]
Symptoms that should raise clinical suspicion include progressive dysmenorrhea, chronic pelvic pain also outside the menstrual period, deep dyspareunia, and infertility. In more complex forms, cyclic dyschezia, cyclic dysuria, and cycle-related bowel or urinary symptoms may also appear. More alarming signs include hematochezia, hematuria, or urinary or bowel obstruction, suggestive of deep endometriosis. On physical examination, the presence of tender nodules at the uterosacral ligaments, rectovaginal septum, or adnexal masses may point toward the diagnosis.
Ref.: [1, 3, 4]
Transvaginal ultrasound is the initial imaging examination recommended by international guidelines and is particularly useful both for identifying endometriomas and for evaluating deep endometriosis. The so-called augmented pelvic ultrasound enables evaluation of the dynamic relationships between pelvic organs, including the presence of "kissing ovaries" and reduced sliding between pelvic structures. MRI with a dedicated protocol is a very useful second-level examination in defining disease extent, particularly when rectosigmoid, bladder, or ureteral involvement is suspected, and provides a panoramic view of the pelvis useful for surgical planning.
Ref.: [1, 5]
Malignant transformation of endometriosis is an infrequent event, estimated overall at approximately 0.5–1% of cases, and is observed predominantly in the ovary. The histologic subtypes most frequently associated are endometrioid carcinoma and clear cell carcinoma. The relative risk of ovarian carcinoma is increased in women with endometriosis, particularly in deep forms and endometriomas, but the absolute risk remains low. The main factors associated with greater risk are older age, postmenopausal status, large cysts, and prolonged estrogen exposure. In light of these data, prophylactic demolitive surgery is not recommended in the absence of specific indications.
Ref.: [1, 6, 7]
Endometriosis, and in particular endometrioma, is associated with a clinically relevant reduction in ovarian reserve. Affected women present lower AMH levels compared with those without the disease, with a more pronounced reduction in cases of ovarian involvement and in infertile patients. More advanced disease stages are also correlated with greater compromise of ovarian function. Ovarian surgery, particularly cystectomy, may cause a further postoperative reduction in AMH levels. For this reason, ovarian reserve assessment is a relevant step in treatment planning.
Ref.: [1, 8, 9, 10, 11]
First-line hormonal therapies include combined oral contraceptives and progestins, used for pain control and management of disease progression. Available evidence shows that these treatments significantly reduce pelvic pain compared with placebo, without substantial differences in efficacy among the various first-line options. The levonorgestrel intrauterine system is also a valid therapeutic option. Second-line therapies include GnRH agonists and antagonists, while aromatase inhibitors are reserved for selected settings. In general, continuous administration aimed at amenorrhea is more effective than cyclic use in controlling pain symptoms.
Ref.: [1, 4]
Surgery is indicated when medical therapy is ineffective, contraindicated, or not tolerated. Surgical treatment may also become necessary in the presence of endometriomas with suspicious features, large cysts, or cases associated with risk of ovarian torsion. In deep endometriosis, surgery is also indicated in cases of hematuria, hematochezia, or obstructive conditions involving the urinary or intestinal tract. For ovarian endometrioma, cystectomy is associated with a reduction in dysmenorrhea and recurrences compared with simple drainage and ablation. The surgical choice must nevertheless be individualized, considering age, symptoms, reproductive desire, and ovarian reserve.
Ref.: [1, 2]
Yes, the correlation is well documented. A high proportion of women with endometriosis report gastrointestinal symptoms such as abdominal bloating, alternating bowel habits, nausea, constipation, or pain during defecation. Patients with endometriosis also present an increased risk of irritable bowel syndrome compared with the general population. Cyclic dyschezia is a particularly suggestive symptom, as is bowel pain that worsens in relation to the menstrual cycle. In deep forms, bowel involvement may cause hematochezia or, more rarely, obstructive presentations. The so-called "endo belly" — cyclic abdominal distension — is also considered a frequent clinical finding.
Ref.: [1, 3, 12, 13]
Endometriosis exerts a significant impact on spontaneous fertility. Infertility affects approximately 30–50% of women with this disease. Affected patients present lower rates of spontaneous conception compared with women without endometriosis and may show an increased risk of spontaneous miscarriage and ectopic pregnancy. The negative effect on fertility is related to multiple mechanisms, including altered ovarian function, tubal compromise, pelvic inflammatory environment, and reduced endometrial receptivity. In mild or moderate forms, spontaneous conception is still possible in a significant proportion of cases, while in more severe forms the probability is substantially reduced.
Ref.: [3, 14, 15, 16]
Lifestyle modifications may contribute to symptom control and management of the inflammatory context associated with endometriosis, although they do not replace medical therapy. Available data suggest a possible benefit of dietary regimens rich in antioxidants, omega-3 fatty acids, vitamins D, C, and E, and low in ultra-processed foods, animal fats, and red meat. Greater adherence to the Mediterranean diet has been associated with a lower probability of endometriosis in observational studies. In selected patients, particularly those with concomitant bowel symptoms, dietary approaches such as the low-FODMAP diet or predominantly plant-based regimens may prove useful. Acupuncture and cognitive behavioral therapy have also shown possible benefit for pain, but definitive recommendations require further high-quality controlled studies.
Ref.: [17, 18, 19, 21]
For information on gynecologic examination and the initial diagnostic pathway for endometriosis, visit the portal dedicated to clinical gynecology.
iltuoginecologo.it → Clinical Gynecology
Request a Specialist Consultation
For a specialist evaluation of ovarian endometrioma — from ultrasound diagnosis to surgical planning and fertility preservation — Prof. Di Donato offers individual consultations at Sapienza University of Rome.
Book a Consultation →