Figures 1-A and 1-B: Axial T1-weighted out-of-phase images demonstrate a T1 hyperintense mass in the
left adnexa (Figure 1-A). There is no India ink artifact surrounding this mass, thus, suggesting that the T1 hyperintensity represents hemorrhagic products. Similar hemorrhagic masses are also seen in the right adnexa (Figure 1-B).

Figures 2-A and 2-B: Axial T2-weighted images demonstrate the left adnexal lesion (Figure 2-A) has a fairly homogeneous, decreased signal “shading.” The differential for “shading” includes endometrioma and hemorrhagic cyst. The right adnexal lesions (Figure 2-B) demonstrate similar homogeneous mild T2 hypointensity.

Figures 3-A and 3-B: Axial subtracted post-contrast images demonstrate no contrast enhancement in the
left adnexal lesion (Figure 3-A) and right adnexal lesions (Figure 3-B).

Endometriosis.

Endometriosis is a generally benign entity defined as the presence of endometrial glands in locations outside the uterus. The ectopic endometrium responds to hormonal stimulation with various degrees of cyclic hemorrhage that result in suggestive symptoms and appearances. Endometriosis has an estimated prevalence of 10% in women of reproductive age. It average age of onset is between the ages of 25 to 29 years and endometriosis is rarely seen in postmenopausal women. Endometriosis in women younger than 20 years is often secondary to obstructive anomalies of the uterus or vagina. The pathogenesis of endometriosis is debated and there are numerous theories that have been postulated, including: (1) reflux of endometrial cells through the fallopian tubes with direct implantation onto pelvic structures; (2) coelomic metaplasia in which totipotential cells are transformed by repeated exposure to hormonal stimuli; and (3) vascular dissemination in which endometrial cells are transported by the blood vessels or lymphatics. The three hallmarks of endometriosis are peritoneal endometrial implants, endometriomas (“chocolate” cysts), and adhesions. The most frequent site of peritoneal involvement is the ovary, specifically termed endometriomas or endometriotic cysts. Endometriomas are usually multiple and bilateral. The next most frequent locations (in order of decreasing frequency) are the uterine ligaments, pelvic cul-de-sac (pouch of Douglas), pelvic peritoneum reflected over the uterus, fallopian tubes, rectosigmoid, and bladder dome. Rare extraperitoneal sites include the lungs and the central nervous system.

Although endometriosis may be an incidental finding, the most common symptoms include chronic pelvic pain and infertility, cyclical pain, dysparenunia, and ovarian masses. Adhesions can obliterate the cul-de-sac, which correlates with the physical examination finding of a “frozen pelvis.” Complications of endometriosis include bowel and ureteral obstruction resulting from endometrial implants, pelvic adhesions, or mass effect from large endometriomas. Although rare (1%), malignant transformation can occur, with the most common tumor types being endometrial carcinoma, clear cell carcinoma, and carcinosarcoma.

Laparoscopy is the standard for the diagnosis and staging of pelvic endometriosis. Staging of endometriosis depends on the degree and complications of endometrial implants. The 1985 Revised Classification of Endometriosis created by the American Society for Reproductive Medicine evaluated characteristics of endometrial implants, such as location and depth of penetration, as well as the degree of cul-de-sac obliteration and adhesions. The findings on laparoscopy can classify patients into four classes from mild (stage I) to severe (stage IV). The staging correlates with likelihood of pregnancy but not with severity of pain. Laparoscopic imaging is limited in endometriosis in that it can not clearly visualize lesions located in regions obscured by pelvic adhesions and lesions located in extraperitoneal sites.

Magnetic resonance (MR) imaging is a promising alternative for the evaluation of endometriosis before treatment with a demonstrated a sensitivity between 90 to 92% and specificity between 91 to 98% for the detection of endometriomas. Endometriomas are thick walled cysts with extensive surrounding fibrosis and adhesions to adjacent structures. On T1-weighted images, endometriomas demonstrate homogeneously high signal intensity, more conspicuous on fat-suppressed T1 weighted images—which also help differentiate these from fat-containing lesions. On T2-weighted images, endometriomas demonstrate a gradient of low signal intensity, termed “shading,” presumably caused by repeated bleeding and the build-up of blood products, especially iron, that shorten T2. This T2 shortening is rarely seen in other masses of any type, e.g. functional or hemorrhagic cysts. The discrete endometrial implants are more difficult to identify, although their imaging characteristics are similar to endometriomas. Some endometrial implants exhibit enhancement after gadolinium. MR imaging can also demonstrate the complications of endometriosis including bowel obstructions and hydronephrosis. MR imaging has limitations, with its main limitation being the detection of small (< 3 mm) peritoneal implants, as well as atypical implants, identifying adhesions, and accurate staging of the disease.

Laparoscopic or surgical diagnosis, staging, and treatment are still often necessary. Treatment for symptomatic endometriosis can be medical or surgical. Nonsteroidal anti-inflammatory drugs (NSAIDs) are frequently used first in patients with pelvic pain, particularly if the diagnosis of endometriosis has not been definitively established. Oral contraceptives can be used to achieve an anovulatory state. Laparoscopic surgical approaches to endometriosis include ablation of implants, lysis of adhesions, removal of endometriomas, uterosacral nerve ablation, and presacral neurectomy. Conservative surgery can be performed to preserve fertility in young patients. Definitive surgery is a hysterectomy and bilateral oophorectomy.

References:

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