Clinical History: A 35 year-old female runner with bilateral hip pain presents for MRI of the pelvis. Sagittal and coronal T2-weighted (1a,b), axial intermediate-weighted with fat suppression (1c), and coronal post-gadolinium T1-weighted with fat suppression (1d) images of the pelvis are provided. What are the findings? What is your diagnosis?
Degenerating uterine fibroid with large areas of necrosis.
Many non-musculoskeletal findings on routine hip and pelvis MRI studies are diagnostic and can simply be reported without the need for further imaging. However, because musculoskeletal pelvic MRI imaging techniques differ from gynecologic pelvic MRI techniques, additional imaging is occasionally indicated for incidentally discovered female pelvic findings. The intent of this article is to help the musculoskeletal radiologist become more comfortable diagnosing and adding clinical value when unexpected female pelvis findings are discovered. This is not meant to be all-inclusive web clinic of gynecologic pathology, but a review of the most common entities upon reviewing thousands of reported cases within our musculoskeletal MRI practice.
Leiomyomas are the most common uterine neoplasm, occurring in 20%–30% of women of reproductive age.1 They are composed of smooth muscle with a varying amount of fibrous tissue and often calcification. Generally, they are asymptomatic; however, they can present with abnormal uterine bleeding and pain depending upon their location and size. Approximately 30% of hysterectomies performed in the United States are for symptomatic leiomyomas; among black women, this number is as high as 50%.2,3 Some researchers find that up to 80% of women with leiomyomas are asymptomatic and require no treatment4 whereas others find that 20%–50% of women with leiomyomas present with symptoms such as menorrhagia, dysmenorrhea, pressure, urinary frequency, pelvic and back pain, dyspareunia, constipation, or obstipation.5 MRI is the most accurate method of evaluation–both for diagnosis and for potential complications. Leiomyomas can be classified as submucosal (Figure 3), intramural (Figure 4), and subserosal (Figures 1 and 2). Large fibroids can outgrow their blood supply with subsequent degeneration altering the appearance. Identifying and describing them will help the clinician appropriately address symptomatic fibroids.
Nondegenerated uterine leiomyomas have a typical MRI appearance: well-circumscribed masses with homogeneously decreased T2-weighted signal intensity compared with the normal myometrium6 and intermediate to decreased T1 signal with mild post gadolinium enhancement (Figure 4). Histologically, non-degenerated leiomyomas are composed of whorls of uniform smooth muscle cells with various amounts of intervening collagen.7 Cellular leiomyomas, which are composed of compact smooth muscles cells with little or no collagen, can have relatively increased T2-weighted signal intensity and demonstrate homogeneous enhancement on contrast-enhanced images.8
Degenerating leiomyomas (Figures 1 and 2) have a varied appearance. Calcified areas will appear as decreased T1 and T2 signal. (Figure 5) Areas of cystic degeneration will appear as fluid which doesn’t enhance. Areas of myxoid degeneration will be of increased T2 signal with minimal gadolinium enhancement. Variable T1-weighted signal intensity and low T2-weighted signal intensity are seen in necrotic leiomyomas that have not liquefied and formed cystic foci.8
Adenomyosis is ectopic endometrial gland tissue and stroma within the myometrium with reactive hypertrophy of the surrounding myometrial smooth muscle.9 Adenomyosis likely results from direct invasion of the basal endometrium into the myometrium. Adenomyosis occurs in focal and, more commonly, diffuse forms.9 Clinically, adenomyosis and leiomyomata can present similarly with dysmenorrhea or menorrhagia.
With MR imaging, the diffuse form of adenomyosis (Figure 6) appears as a thickened junctional zone (inner myometrium) on T2-weighted images.10A junctional zone measuring 12 mm thick or greater is highly predictive of adenomyosis.10 The low signal intensity of adenomyosis on T2- weighted images is due to the reactive, dense smooth muscle hypertrophy that surrounds the embedded endometrial glands.11 Small foci of high signal intensity on T2-weighted images represent the ectopic endometrial glands. Some of these ectopic endometrial glands also have corresponding high signal intensity on T1-weighted images, corresponding to functional hemorrhage.12,13
The focal form of adenomyosis appears as a poorly marginated area of low signal intensity within the myometrium on T2-weighted images.12 This has a similar appearance to a leiomyoma though less well-defined.
In the United States, endometrial cancer is the most common malignancy of the female pelvis. Endometrial adenocarcinoma accounts for 90% of the endometrial cancers.14 The typical MRI appearance (Figure 7) is of a mass in the endometrium with T1 signal of or lower than normal endometrium and intermediate T2 signal, lower than the endometrium but greater than the myometrium. The mass demonstrates less post-gadolinium enhancement than the myometrium.15 Other findings suspicious for an endometrial cancer are fluid within the endometrial canal of a post-menopausal patient along with irregularity of the endometrium, an irregular mass within the canal, or disruption of the interface of the endometrium with the myometrium.14
Uterine sarcomas are rare, representing only 2-6% of uterine malignancies. Approximately one-third of uterine sarcomas are leiomyosarcomas.16 They can originate from the connective tissue of uterine blood vessels, in a preexisting leiomyoma, or de novo from uterine musculature.17 However, the prevalence of a benign uterine leiomyoma undergoing sarcomatous change is reported to be only 0.1%–0.8%.18 A leiomyosarcoma usually presents as massive uterine enlargement with irregular central zones of extensive hemorrhage and necrosis, possibly with calcific foci. The opening case in question (Figures 1 and 2) has an appearance suspicious for leiomyosarcoma. An irregular margin of a uterine leiomyoma on MRI is suggestive of sarcomatous transformation, but the specificity of this finding is unknown.17
A septate uterus (Figures 8 and 9) is one form of Mullerian duct anomaly (MDA) that arises from interruption of normal uterine development. MDAs are a broad spectrum of abnormalities that are often associated with primary amenorrhea, infertility, obstetric complications, and endometriosis. They are commonly associated with renal and other anomalies. However, MDAs are not associated with ovarian anomalies.19 The difference between a septate and a bicornuate uterus is determined by the thickness of the fundal contour. The septate uterus maintains a normal fundal contour where a bicornuate uterus has a distinct concavity. A septate uterus, the most common form of MDA, can be complete or partial.
Nabothian cysts are very common incidental findings, representing rentention cysts of the cervical glands due to chronic inflammation and scarring.20
The fluid signal appearance is due to the accumulation of mucus. Nabothian cysts can be single or multiple within the cervical fibrous stroma, are round, and have regular borders. They are of increased T2 signal and of intermediate to slightly increased T1 signal (Figure 10).
Benign leiomyomas typically occur in the uterine body and fundus. However, rarely they can arise in the cervix, accounting for 0.6-10% of uterine leiomyomata.21 The MRI appearance (Figure 11) is the same as for a uterine leiomyoma.
Cervical carcinoma typically occurs in younger women with an average patient age of 45 years.22 Cervical carcinoma has intermediate T2-weighted signal intensity, which can be seen as a disruption in the normal band-like low signal fibrous stromal ring. Cervical carcinoma can have a wide variety of morphologic features including being exophytic, infiltrating, or endocervical with a barrel shape. In young women, cervical carcinoma usually originates from the squamocolumnar junction and tends to be more exophytic; in older women it originates more often in the endocervical canal. The bulk of the tumor is centered at the level of the cervix but may protrude into the vagina or invade the lower myometrium.23
Simple ovarian cyst
A simple, unilocular ovarian cyst (Figure 12) is a common incidental ﬁnding in both pre- and postmenopausal women. However, the postmenopausal ovary tends to contain fewer cysts of smaller size. When <3 cm in size, demonstrating a thin wall (≤3 mm), and simple fluid characteristics, these cysts can be considered benign in both populations. Studies that speciﬁcally examined the premenopausal ovary have shown the risk of malignancy in unilocular cysts less <5 cm in an asymptomatic woman approaches zero.24
Hemorrhagic ovarian cyst
The MRI appearance of a hemorrhagic ovarian cyst (Figure 13) can be variable, depending on the age and amount of the hemorrhagic component. In general, they tend to contain high T1 signal, intermediate to high T2 signal, and frequently demonstrate a ﬂuid-ﬂuid level. Hemorrhagic cysts should retain high signal on fat-suppressed T1-weighted images, which differentiates them from dermoids. Hemorrhagic cysts also tend to have thicker walls than simple cysts and may exhibit post-contrast wall enhancement.24
Most dermoids are unilocular, contain sebaceous ﬂuid, and are commonly referred to as mature cystic teratomas or dermoid cysts. Although these are usually asymptomatic and are incidental ﬁndings in young women, the standard treatment is surgical removal because of their potential to cause ovarian torsion or for the cyst to rupture. There is also a rare chance of malignant degeneration to squamous cell carcinoma.24
MRI has a high sensitivity for the presence of fat within the sebaceous component, which is characteristic of nearly all these lesions. (Figures 14 and 15) The sebaceous component is of very high signal intensity on T1-weighted images and is somewhat variable on T2-weighted images.25 Fat suppression can differentiate the fat content from other hemorrhagic lesions that appear hyperintense on T1-weighted images, such as hemorrhagic cysts and endometriomas.
An endometrioma is a collection of uterine endometrial cells that implant, commonly on the ovary, and enlarge and repeatedly hemorrhage in response to hormonal stimulation.26 A cystic lesion with a hyperintense focus on a T1-weighted images with corresponding relative decreased signal on a T2-weighted images (termed “T2 shading”) (Figure 16) is the classic appearance of an endometrioma.26 However, this T2 shading can also be seen in other hemorrhagic adnexal lesions, particularly a hemorrhagic cyst, with a specificity for endometrioma of only 83%.27 The additional finding of a T2 dark spot along but not within the cyst wall, when not also of decreased T1 signal as can be seen with calcification, and in the absence of post-gadolinium enhancement, is specific for chronic hemorrhage and thus has higher specificity for an endometrioma (Figure 17).28 In one study, the T2 dark spot was seen in 36% of the endometriomas; thus the absence of this sign does not preclude the diagnosis of an endometrioma.28 Endometriomas can also often be strikingly dark on T2 weighted images (Figure 18).
Serous cystadenoma (Figure 19) is a benign tumor that usually present as an unilocular cyst with a regular wall less than 3 mm thick, flat internal margins without internal septations, papillary projections or solid components, and with no significant contrast enhancement. Serous fluid shows low signal intensity on T1-weighted and high signal intensity on T2-weighted images similar to water. They are usually smaller and more often bilateral than mucinous cystadenomas. Serous cystadenomas of borderline malignancy may demonstrate small papillary projections.29
Serous cystadenofibroma (Figure 20) is a relatively rare, benign ovarian tumor. It often has a complex appearance on MRI, with both cystic and solid components, and can resemble a malignancy, due to the presence of irregular, thickened septations or nodular components. The fibrous component of the tumor demonstrates low-signal intensity (relative to skeletal muscle) on T2-weighted images.30
Mucinous cystadenoma (Figure 21) is a benign mucin-containing tumor, often larger than serous cystadenoma and usually unilateral. It usually appears as a multilocular cystic lesion with a thin regular wall and several septations, without solid components or nodularity and show no significant gadolinium enhancement. Rupture of a mucinous cystadenoma can produce pseudomyxoma peritonei.29
Pelvic venous congestion syndrome
Pelvic venous congestion syndrome (PVCS) is a challenging diagnosis and complex cause of chronic pelvic pain in female patients. PVCS can result from incompetent vein valves with gonadal vein reflux and pelvic venous engorgement. However, pelvic venous engorgement and gonadal vein reflux can be seen in patients without pelvic pain. Thus, MRI imaging alone is not specific for the diagnosis, but rather suggestive. The underlying cause of PVCS may be incompetent gonadal vein valves or structural causes such as left renal vein compression with an incompetent gonadal vein valve (nutcracker syndrome) or iliac vein compression (May-Thurner configuration) with reflux into the ipsilateral internal iliac vein.31 MRI findings that suggest PVCS are dilated parauterine varices, heterogeneous or T2-hyperintensity due to slow flow, presence of an arcuate vein crossing the midline, and vulvar and/or thigh varices.31
Serous cystadenocarcinoma is the most common ovarian neoplasm and is responsible for about 40% of malignant ovarian neoplasms. Mucinous cystadenocarcinoma is less common and accounts for about 10% of ovarian malignancies. These tumors are seen as complex multilocular masses, usually with thick and irregular walls, septations, solid components and papillary projections of low signal intensity on T2-weighted images with contrast enhancement after gadolinium administration. The serous fluid of the cystic components has low to intermediate signal intensity on T1-weighted and high signal intensity on T2-weighted images. Some cases of serous cystadenocarcinoma demonstrate psammomatous calcifications. The signal intensity of mucinous content is variable depending on mucin concentration. These tumors can be very large, even greater than 12–15 cm. Serous cystadenocarcinoma is more frequently bilateral than mucinous cystadenocarcinoma.29
Bartholin gland cyst
Bartholin glands arise in the superficial perineal pouch of the urogenital triangle, and the ducts open into the posterolateral aspect of the vaginal vestibule. Ductal obstruction due to previous infection or inspissated mucus leads to retention of secretions and cyst formation. Bartholin gland cysts are the most common vulvar cysts, ranging in size from 1 to 4 cm, but can increase in size with repeated sexual stimulation.32 They are solitary round to oval cysts and are low to intermediate in signal intensity on T1-weighted sequences, depending on the mucin content of the cyst fluid, and are hyperintense on T2-weighted sequences. Simple cysts are thin-walled and unilocular, but septations can be seen. The cyst wall may be thickened and enhances if infected.33 The cysts arise within the superficial perineal pouch, inferior to the perineal membrane; on sagittal images they are seen below the inferior margin of the symphysis pubis.32
Routine orthopaedic MR imaging of the hips, sacrum, and sacroiliac joints commonly reveals non-musculoskeletal findings in a female pelvis. Due to the techniques and field of view typically used in orthopaedic MR, these abnormalities may not always be adequately evaluated. However, it is incumbent upon the musculoskeletal radiologist to detect the pathology, make the diagnosis when possible, and guide the ordering physician when further workup is necessary.
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- Viswanathan M, Hartmann K, McKoy N et al.. Management of uterine fibroids: an update of the evidence. Evidence report/technology assessment no. 154, AHRQ publication no. 07-E011. Rockville, Md: Agency for Healthcare Research and Quality, 2007. ↩
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