Endometriomas usually present as a pelvic mass arising from growth of ectopic endometrial tissue within the ovary. They typically contain thick brown tar-like fluid (hence the name "chocolate cyst") and are often densely adherent to surrounding structures, such as the peritoneum, fallopian tubes, and bowel. An endometrioma may be associated with symptoms of endometriosis (eg, pelvic pain, dysmenorrhea, and dyspareunia) or identified at the time of evaluation for a pelvic mass or infertility. A woman with a ruptured endometrioma may initially present with peritoneal signs and symptoms, elevated white blood cell count, and low grade fever, similar to patients with acute pelvic inflammatory disease or appendicitis.
The diagnosis and management of endometriomas will be discussed here. General issues relating to endometriosis are reviewed separately. (See "Pathogenesis, clinical features, and diagnosis of endometriosis" and "Overview of the treatment of endometriosis".)
The pathogenesis of endometriomas is not clear. One hypothesis is that retrograde passage of menstrual blood or shedding from endometriosis implants deposit on the ovary. Progressive invagination of the ovarian cortex over these deposits then leads to formation of an endometrioma, which is actually a pseudocyst . The cyst contents of endometriomas contain high concentrations of iron, presumably from chronic bleeding into the cyst, possibly at the time of menses.
Histopathology is required to make a definitive diagnosis of endometrioma. However, a clinical diagnosis can often be made with a high degree of certainty in a woman with histologically confirmed endometriosis and an adnexal mass, since 50 percent of women with endometriosis develop endometriomas, which are often bilateral .
Ultrasound is useful for supporting the clinical diagnosis of endometrioma, but of limited value for diagnosis or determining extent of endometriosis at other sites since it lacks adequate resolution for visualizing adhesions and superficial peritoneal/ovarian implants. However, when there are sonographic signs suggestive of endometriomas, it is likely that moderate to severe endometriosis is present; therefore, if pain is the presenting problem, extensive surgery may be required for relief of pain .