Low-level internal echoes within an endometrioma

Wall calcification within an endometrioma

Large endometrioma with thickened wall, internal low-level echoes and thin septation


Pelvic sonography demonstrates a cystic adnexal mass with a thickened wall and internal echoes. At laparoscopy this proved to be an endometrioma. Two additonal cases of endometriomas are demonstrated; one with a wall calcification and the other with a thin septation.


Endometriosis is a disease process in which functioning endometrial tissue is present in an abnormal and ectopic location, outside of the uterus. This tissue is most commonly seen in the cul-de-sac with deposits on the serosal surfaces. The posterior leaf of the broad ligament, ovaries, fallopian tubes, uterus, colon and bladder are commonly affected however ectopic endometrial tissue has been reported affecting the kidneys, liver, pleural space, extremities and abdominal wall, as well. Endometriosis most commonly affects women of reproductive age with reports of between 5% and 20% of these women being affected. It has been estimated that endometriosis is a cause of infertility in 20% to 45% of women. Pathologically, endometriomas are often diagnosed by the presence of endometrial epithelium, glands or stroma, or hemosiderin-laden macrophages in an adnexal mass. Clinically patients may present with pelvic pain, however there is no predictable relationship between the patients symptoms and the extent of disease at surgery.

When the endometrial deposits become walled off and develop internal hemorrhage they become endometriomas. Sonographically, detection of the endometrioma is the real only clue to the presence of this disease process. There have been numerous reports describing the ultrasound appearance and sensitivity for the detection of endometriomas. In a study by Kupfer et al they found the most common appearance for an endometrioma was that of a cystic pelvic mass which contained homogeneous low-level echoes (found in 82% of their patients). A report by Fried et al analyzed 51 proven cases of endometrioma. They found 30% were purely cystic, 62% were cystic with few septations or minimal debris and 8% were essentially solid. Their analysis as well as others have pointed out that, as expected, the appearance follows the natural course of hematoma resolution. Lesions may begin as homgeneously gelatinous structures which appear cystic, then develop partial resolution and liquifaction and ultimately are purely cystic. The difference between this study and others in describing the appearance of the lesion as cystic, etc is largely a semantic one. Other authors use the term cystic to describe unilocular lesions with low-level internal echoes, however no soft-tissue or sepatations. In their study the average diameter of endometriomas was 6.1 cm. (range 2.0 to 20 cm.). A number of studies have examined the accuracy for the sonographic detection of endometriosis utilizing transabdominal, transvaginal and color Doppler evaluation. Sensitivities ranging from 75% to 89% have been reported. A recent study by Alcazar et al demonstrated no statistically significant difference in the resistive index of endometriomas from non-endometriomas. In addition, while they did find the color Doppler pattern originally described by Kurjak (pericystic vessels at the level of the ovarian hilus) in as many as 90% of their patients, it was also found in other cystic ovarian masses. Their conclusion was that color Doppler did not improve the diagnostic accuracy.

Hemorrhagic cyst (Low-level echoes from fibrinous strands within the cyst)

MRI of the pelvis (Fat-supression technique)

While the pattern of a cystic mass with low level echoes is frequently seen in endometriomas it can be seen in a number of other adnexal masses. The differential diagnosis includes: hemorrhagic ovarian cysts, pelvic inflammatory disease, tubo-ovarian abscess, ovarian neoplasms, ectopic pregnancy and ligamentous fibroids. In the authors experience the two most common confusing entities are a hemorrhagic or dermoid cyst. Persistence of the lesion at a relatively stable size over time may be helpful in defining this lesion. On the other hand, no appearance should be considered exclusionary of the disease and patients may need laparoscopy for confirmation. Magnetic resonance imaging (MRI) is helpful in many patients.


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Fried AM; Rhodes RA; Morehouse IR. Endometrioma: analysis and sonographic classification of 51 documented cases Southern Medical Journal, Mar;86(3):297-301,1993

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Alcazar JL, Laparte C, Jurado M, Lopez-Garcia G. The role of transvaginal ultrasonograpy combined with color velocity imaging and pulsed Doppler in the diagnosis of endometrioma. Fertility and Sterility 67:487-491, 1997

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