- Email: [email protected]
Adnexal Masses in Pregnancy
Adnexal Masses in Pregnancy Margaret Yacobozzi, MD, Dustin Nguyen, DO, and Dmitry Rakita, MD Adnexal masses are often seen in the gravid patient. With current advances in technology, an increased number of adnexal masses are incidentally discovered on antenatal screening ultrasonography examinations. Sonography is the first-line imaging modality for any adnexal mass. However, further evaluation with magnetic resonance imaging (MRI) may be critical for diagnosis. For example, MRI can determine whether a mass contains fat, which can be useful in the diagnosis of a teratoma. Characteristic features of nonneoplastic and neoplastic ovarian lesions seen on sonography and MRI will be discussed. Radiologic features that help distinguish benign from malignant neoplasms will be described. Additional lesions specific to the gravid state must be considered in the differential diagnosis when appropriate, such as hyperstimulated ovaries, hyperreactio luteinalis, theca lutein cyst, and luteomas. Semin Ultrasound CT MRI 33:55-64 © 2012 Published by Elsevier Inc.
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dnexal masses are incidentally found on routine screening examinations in pregnancy. With the technologic advances in ultrasonography, the incidence of adnexal masses in gravid patients has increased. It is essential to recognize the sonographic features of particular adnexal masses seen in the pregnant patient to help establish a diagnosis and guide clinical or surgical management. In addition, understanding the role of magnetic resonance imaging (MRI) in the diagnosis of adnexal masses and the appearance of various adnexal masses on MRI is imperative.
Ultrasonography and MRI Techniques Ultrasonography is the first-line imaging modality used for evaluating adnexal masses during pregnancy. Ideally, both transabdominal and transvaginal techniques are used. Twodimensional ultrasonography is typically used, but in certain cases, 3-dimensional ultrasonography may be valuable. Doppler ultrasonography is a critical tool in the characterization of masses. For example, the presence of color flow within a septum or solid component of the mass may increase suspicion for malignancy. Sonography also serves as a useful modality for following the progression or regression of adnexal masses. Department of Radiology, Tufts School of Medicine, Baystate Medical Center, Springfield, MA. Address reprint requests to Margaret Yacobozzi, MD, Department of Radiology, Baystate Medical Center, 759 Chestnut Street, Springfield, MA 01199. E-mail: [email protected]
0887-2171/$-see front matter © 2012 Published by Elsevier Inc. doi:10.1053/j.sult.2011.10.004
For the up to 20% of sonographically indeterminate adnexal lesions, MRI is used as a second-line imaging modality.1 MRI is useful in evaluating adnexal masses that are too large to be accurately evaluated by ultrasonography. Specific MRI techniques are used to obtain diagnostic images. Patients should fast for 4 hours before an MRI examination to limit artifact from bowel peristalsis. Generally, the patient should be scanned in the supine position. However, it may be necessary to scan in the left lateral decubitus position in the later stages of pregnancy to avoid inferior vena cava compression. A body array coil placed over the pelvis is used. Rapid imaging is performed with multislice-spoiled gradient echo for T1 images and single-shot rapid acquisition relaxation-enhanced sequences for T2 images. Image acquisition can be obtained during a maternal breath-hold, respiratory triggered, or free breathing.2 Before performing an MRI on pregnant patients, the potential risks must be explained. There is no evidence to prove that MRI is safe with respect to the fetus. However, no teratogenic/carcinogenic effects have been documented. A balance must be found between the necessity of information that will be gained by performing an MRI versus the undocumented safety of MRI during pregnancy. It is preferable that MRI not be performed before organogenesis. Gadolinium-based contrast is a pregnancy category C drug, with animal studies indicating increased skeletal malformations in offspring of exposed animals. Gadolinium-based contrast can enter the fetal circulation through the placenta and then be excreted by the fetal kidneys, leading to the contrast agent accumulating in the amniotic fluid. 55
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Nonneoplastic Lesions Pregnancy-Associated Cysts Pregnancy-associated cysts include corpus luteum, hemorrhagic, and follicular. Many of the adnexal cystic masses will resolve spontaneously. In fact, it has been reported that 90%100% of cystic masses ⬍5 cm in pregnant patients resolve spontaneously.3 Larger cysts, even when benign, can be associated with torsion, rupture, and labor obstruction. These larger cysts require monitoring and possibly surgery. Corpus luteum cysts form after ovulation and persist for 5-9 weeks of pregnancy. These cysts produce progesterone before the placenta and are essential to maintenance of the pregnancy. Usual resolution of the corpus luteum cyst occurs at 8 weeks. On ultrasonography, the appearance of corpus luteum cysts varies in part because of varying components of hemorrhage. They may appear to be simple or complex. Characteristically, on Doppler ultrasonography, a peripheral ring of color is demonstrated, called a “ring of fire” (Fig. 1). The size of these cysts ranges from 2.5 to 6 cm.4 The walls of corpus luteum cysts are thicker than follicular cysts. The MRI appearance of corpus luteal cysts also varies because of the differing components contained within the cyst. Usually, increased T1 signal intensity is demonstrated with correlating low T2 signal intensity. The appearance of hemorrhagic cysts also differs because of varying stages of clot evolution. Hemorrhagic cysts are generally anechoic masses with internal hypoechoic material and increased sound through transmission. In acute hemorrhage, a hemorrhagic cyst may be echogenic on sonography. A specific sonographic feature of hemorrhagic cysts includes a reticular pattern of blood products. Later in the evolution of hemorrhagic cysts, solid and cystic components can be dis-
Figure 2 Ultrasonography of a normal ovary demonstrates multiple anechoic follicles, all measuring ⬍2 cm.
tinguished, with the solid component representing a retracting clot.5 The MRI appearance of a hemorrhagic cyst is again variable, typically manifested by uniform or dependently layering high T1 and low T2 signal. MRI may not always be conclusive in the diagnosis. A follicle is a simple functional cyst influenced by hormonal changes. A follicular cyst can be seen when a follicle does not spontaneously regress. By definition, a mature follicle is ⬍2 cm in diameter, whereas follicular cysts are ⬎2.5 cm. These cysts are anechoic on sonography and homogeneously T2 bright on MRI (Fig. 2).
Endometriomas
Figure 1 Anechoic corpus luteum cyst demonstrates peripheral color flow on Doppler ultrasonography, referred to as a “ring of fire.” (Color version of figure is available online.)
The prevalence of endometriomas is 3%-10%.4 Although many of these regress, some remain stable for months or can even enlarge. Up to 95% of endometriomas demonstrate diffuse homogenous low-level internal echoes.6 However, endometriomas can vary in appearance from largely cystic to solid, and their appearance can occasionally mirror that of hemorrhagic cysts. Associated calcifications can be seen, which are usually large enough to exhibit acoustic shadowing. Hemorrhagic products account for high T1 and a low T2 signal on MRI (Fig. 3). Endometriomas can be homogeneously low signal on T2-weighted images or can exhibit T2 “shading,” which is a gradual transition from high T2 to low T2 signal. Identifying fibrous bands of adhesions in the pelvis on MRI strongly supports the diagnosis of endometriosis. It has been reported that MRI is 68% sensitive and 83% specific in diagnosing endometriotic cysts from other hemorrhagic lesions.7 Unique to pregnancy and its progestational effects, ectopic decidualization of the wall of an endometrioma may be seen. Sonography may demonstrate solid vascular nodules within
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Germ Cell Tumors
Figure 3 Axial T2 (A) and fat-suppressed T1 (B) images demonstrating an intermediate T2 and high T1 signal mass in the left adnexa (arrow). This is an example of an endometrioma.
the wall of an endometrioma, mirroring the vascular decidual lining of the uterus. This appearance may raise concerns for malignancy, and an MRI may be done for further investigation. In ectopic decidualization, the solid vascular component of the endometrioma will resemble the MRI appearance of the uterine decidual lining in early pregnancy.2
Neoplasms Cancer and pregnancy have a rate of association of 1/1000 live births.8 Twelve and a half percent of ovarian cancers are seen in women ⬍40 years old.9 Six percent of adnexal masses excised during pregnancy were found to be malignant.10 Evaluating the gravid patient for ovarian cancer has added complications. Tumor markers that can be used in nonpregnant patients may already be elevated, as in cancer antigen 125. This makes imaging even more important in the workup of adnexal masses in the pregnant patient.
Teratomas are included within the category of germ cell tumors. After 16 weeks of gestation, teratomas are the most common adnexal cystic lesion. Teratomas may be bilateral in approximately 10%-13.2% of cases.11 These lesions have an approximately 2% rate of malignant transformation, which will most commonly be of the invasive squamous carcinoma type. Pregnancy complications secondary to these lesions are uncommon when masses are ⬍6 cm. On ultrasonography, mature cystic teratomas, or dermoids, have several characteristic features. Hyperechoic nodules with distal acoustic shadowing may be seen, referred to as a “dermoid plug.” “Tip of the iceberg phenomenon” occurs when echogenic areas of the teratoma attenuate the ultrasonography beam. This causes the back wall of the cyst to be obscured by acoustic shadowing. Hair and sebum in teratomas cause hyperechoic lines and dots, leading to the “dermoid mesh” pattern. Less commonly, a fluid-fluid level may be seen in which the nondependent portion is hyperechoic fat and the dependent layer is more hypoechoic fluid. Teratomas may contain echogenic floating balls (representing fat) within a cystic structure. MRI can be useful when the sonographic appearance is nonspecific. Mature cystic teratomas demonstrate the chemical shift artifact at least 62% of the time12 (Fig. 4). Selective chemical fat-suppression technique can be used to distinguish cystic teratomas from hemorrhagic adnexal processes with a sensitivity of 92%.12 Dermoids are high intensity on T1 and T2 sequences. Dysgerminomas also fall within the spectrum of germ cell tumors. Excluding epithelial tumors of low malignant potential, dysgerminomas are the most common invasive malignant neoplasm in pregnancy. These masses do carry a good prognosis, as they are sensitive to chemotherapy and radiation. On sonography, these lesions appear as a solid mass. However, if there is necrosis, the mass may contain anechoic components. On MRI, dysgerminomas demonstrate increased signal intensity on T2-weighted images, with presence of T2 hypointense septations.13
Fibromas Fibromas are included in the category of sex cord-stromal tumors, which account for one-fifth of ovarian malignancies found during pregnancy. On ultrasonography, these masses appear hypoechoic and solid, although they may contain cystic components (Fig. 5). In approximately 18%-52% of cases, they demonstrate acoustic shadowing, similar to uterine fibroids.14 In fact, it may be difficult to separate fibromas from uterine fibroids when the fibroma grows as an exophytic ovarian mass. When detected by MRI, these masses demonstrate characteristic low T2 intensity because of the fibrocollagenous stroma.13 Fibromas are intermediate signal on T1-weighted images (Fig. 6). Granulosa cell tumors are also included within the spectrum of sex cord-stromal tumors and rarely occur in pregnancy. Typically, granulosa cell tumors present at stage I, and the patient can be cured surgically. They can be solid or be
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Figure 4 Large right adnexal mass with a fat–fluid level. (A) Fat-saturated T2-weighted image demonstrates bulk fat suppression, whereas (B) opposed phase images demonstrate signal loss of the fat mixed with fluid. This is characteristic of a dermoid.
multilocular with solid components. Intratumoral hemorrhage can occasionally be demonstrated on MRI.
Ovarian Epithelial Neoplasms Up to one-half of ovarian malignancies in pregnancy are ovarian epithelial neoplasms. These neoplasms include cystadenomas, cystadenocarcinomas, and tumors of low malignant potential.
Cystadenomas Cystadenomas account for 40%-50% of benign ovarian neoplasms in the general population, with serous cystadenomas being more common than the mucinous type. On ultrasonography, serous cystadenomas may resemble a simple cyst that is larger than a typical functional cyst. Thin septa-
tions or, occasionally, papillary projections may also be present. When a serous cystadenoma is suspected, it is of increased importance to evaluate the contralateral ovary; bilaterality is seen in up to 20% of cases.8 On MRI, serous cystadenomas have the expected appearance of a cystic lesion with high T2 and low T1 signal intensities. The occurrence of malignant transformation of serous cystadenomas is not substantiated, but is thought to be uncommon if it does occur. The possibility of a simple cyst-like lesion having malignant potential is the impetus to follow-up simple cysts. However, lack of interval growth on a short-term follow-up examination is not necessarily adequate to exclude cystadenomas, as they may be slow growing. Mucinous cystadenomas are multilocular cysts containing fluid of various viscosities.13 Reflecting this, sonographic im-
Adnexal masses in pregnancy
59 mural wall nodules and papillary projections. It is not always possible to discriminate between tumors of low malignant potential and other ovarian epithelial neoplasms. For example, mucinous cystic tumor of borderline malignancy does not have distinguishing features from a mucinous cystadenoma.
Metastatic Ovarian Tumors Ten percent of ovarian cancers are secondary to metastatic disease. However, metastatic ovarian tumors are less com-
Figure 5 Gray-scale ultrasonography image demonstrating a hypoechoic solid left ovarian mass with acoustic shadowing. This was a biopsy-proven ovarian fibroma.
ages of these lesions demonstrate low-level internal echoes with multiple thin septae (Fig. 7). As in serous cystadenomas, the mucinous type can contain papillary projections. However, unlike the serous type, mucinous cystadenomas are rarely unilocular. Because of overlapping appearances, serous versus mucinous cystadenomas cannot be distinguished by ultrasonography. On MRI, the loculi of mucinous cystadenomas appear as varying intensities on T1and T2-weighted imaging because of the varying viscosity of components. This is referred to as a “stained glass” appearance.15
Cystadenocarcinomas Serous and mucinous cystadenocarcinomas are both multilocular cystic masses with features of malignancy not seen in cystadenomas. These features include thicker septations, papillary projections ⬎3 mm in size, and irregular walls (Figs. 8 and 9). Mural and septal nodules with color flow on Doppler analysis are also seen in cystadenocarcinomas.13
Tumors of Low Malignant Potential Tumors of low malignant potential are masses with histological features of malignancy without invasion into the ovarian stroma. These tumors are most common in women of childbearing age. On ultrasonography, tumors of low malignant potential may demonstrate an “ovarian crescent sign,” which is when a rim of normal-appearing ovarian tissue can be visualized adjacent to the tumor. When this sign is present, it argues against invasion of the tumor into the ovary. Features of malignancy are seen in these lesions, including vascular
Figure 6 Magnetic resonance image (MRI) of the same patient as in Fig. 4. Left ovarian fibroma (arrow) is low intensity on T2weighted imaging (A) and intermediate to low signal on T1weighted imaging (B).
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Figure 7 Ultrasonography image of a large anechoic cystic structure with a daughter cyst (within calibers). This was a biopsy-proven mucinous cystadenoma.
monly seen in the pregnant population. The most common primary tumors to metastasize to the ovaries are breast, intestinal, and gastric cancers, as these neoplasms spread via blood vessels and lymphatics. There are similarities in the appearances between primary and secondary ovarian tumors. However, bilaterality is significantly greater in metastatic tumors. Ovarian tumors are
Figure 9 Coronal MRI T1-weighted precontrast image (A) and T1 fat-saturated postcontrast image (B) showing a complex cystic mass with enhancing solid components (arrow). This was a biopsyproven cystadenocarcinoma.
Figure 8 Ultrasonography demonstrating a complex right adnexal mass with vascular solid components and septae (arrowhead). This was a biopsy-proven cystadenocarcinoma. (Color version of figure is available online.)
usually solid, but also may appear as cystic masses. It is rare, however, for an ovarian metastasis to present as a thin-walled simple cyst. Krukenberg tumors are solid bilateral metastatic ovarian malignancies that arise from signet-ring cell carcinomas, most commonly gastric in origin. These tumors may have significant collagen formation, leading to hypointensity on T2 images. Alternatively, Krukenberg tumors may demonstrate considerable edema, correlating with hyperintensity on T2-weighted images.16
Adnexal masses in pregnancy
Pregnancy-Related Lesions Hyperstimulated Ovaries Hyperstimulated ovaries are primarily seen in patients after ovulation induction. On ultrasonography, ovaries are enlarged and demonstrate the characteristic “spoke wheel” appearance.8 This refers to central echogenic ovarian stoma with peripheral ovarian cysts. Ovarian hyperstimulation syndrome is categorized into mild, moderate, or severe based on the amount of ovarian enlargement and patient weight gain. This condition spontaneously resolves in 90% of patients.17 Patients with hyperstimulated ovaries are at increased risk for torsion secondary to ovarian enlargement.
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Theca Lutein Cysts Theca lutein cysts occur with a normal ovarian response to elevated levels of hCG. Therefore, conditions that increase hCG levels, such as gestation trophoblastic disease, multiple pregnancies, and gonadotrophin therapy for infertility, place patients at risk for this condition. Sonographically, the ovaries are enlarged and contain multiple cysts, analogous to hyperreactio luteinalis. On MRI, bilateral ovarian enlargement secondary to multiple thin-walled cysts is seen. Because of ovarian enlargement, an increased risk of torsion exists. Following treatment of the underlying cause of elevated hCG, ovaries return to baseline.
Luteoma of Pregnancy Hyperreactio Luteinalis Hyperreactio luteinalis occurs when patients have increased sensitivity to circulating hCG. Hyperreactio luteinalis typically manifests in the third trimester of pregnancy. Clinically, patients may be asymptomatic or may present with abdominal pain and distention, abnormal liver function tests, respiratory difficulties, or hirsutism.8 Maternal virilization can occur in 14%-25% of women with hyperreactio luteinalis. These patients, by definition, have not undergone ovulation induction. Patients with hyperandrogenism, such as in polycystic ovarian syndrome, are at risk for developing this condition. On both ultrasonography and MRI, the ovaries are enlarged and have multiple peripheral cysts, similar to hyperstimulated ovaries (Fig. 10). However, there is relatively less ovarian enlargement. Spontaneous regression of cysts is seen after delivery.
Luteoma of pregnancy occurs when proliferation of luteinized stromal cells replaces the normal ovarian parenchyma. This occurs under the influence of hCG. The proliferated stromal cells are capable of producing androgens, which may cause maternal virilization as well as virilization of the female fetus. On ultrasonography, luteomas appear as heterogeneous, predominantly hypoechoic masses. Considerable vascularity may be demonstrated on Doppler analysis. Overall, however, the appearance of luteomas is nonspecific, and the diagnosis must be based on both clinical and radiologic findings. The condition will regress along with decreasing androgen levels.
Paraovarian Masses Paraovarian lesions are almost always of benign etiology. Therefore, the ability to distinguish ovarian from paraovarian locations is of value. This can be done by attempting to separate the lesion from the ovary with direct probe pressure during a transvaginal examination. MRI may be helpful to define a lesion as extraovarian by identifying a normal ovary separate from the questioned structure.
Cysts Paraovarian cysts are typically located in the mesosalpinx between the fallopian tube and ovary. These cysts usually range between 1 and 2 cm in size. On imaging, paraovarian cysts demonstrate the same characteristics seen in cysts throughout the body; they are thin-walled anechoic structures on ultrasonography and T2 hyperintense and T1 hypointense on MRI (Fig. 11). Paraovarian cysts are common and are of no clinical significance.
Hydrosalpinx
Figure 10 Ultrasonography images from a pregnant female demonstrating enlargement of the ovary with multiple peripheral anechoic cysts (one demarcated with calibers). This patient was diagnosed with hyperreactio luteinalis by her obstetrician.
Hydrosalpinx is dilatation of the fallopian tube with fluid. Dilatation occurs following distal obstruction of the fallopian tube by adhesions. Common causes of hydrosalpinx are salpingitis and pelvic endometriosis. Hydrosalpinx appears as a tubular anechoic cystic structure that remains unchanged throughout pregnancy (Fig. 12). The most specific finding on ultrasonography is the “waist sign,” indicating that there are 2 diametrically opposed indentations in the wall of the fallopian tube.18 In chronic hydrosalpinx, the “string of beads sign” may be seen. This refers to small nodules along the wall of the fallo-
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Figure 13 Ultrasonography in a patient with pelvic pain demonstrates an enlarged ovary with a ground glass appearance. This was surgically proven to represent a torsed ovary. Figure 11 Ultrasonography examination reveals an anechoic cyst (arrow) between the uterus and the ovary, characteristic of a paraovarian cyst.
pian tube, correlating with thickened folds. MRI may be helpful in cases when it is unclear whether the cystic structure seen on ultrasonography is definitely separate from the ovary.
Leiomyomas Leiomyomas are the most common solid adnexal mass found in pregnancy. Although the most common location of a leio-
myoma is the uterine body, these masses may simulate an ovarian mass when pedunculated. Clinically, patients with leiomyomas may present with acute pain because of degeneration, hemorrhage, or torsion of the mass. Ultrasonography examinations can be beneficial in diagnosing patients because of its real-time capability. If pressure is applied by an ultrasonography probe directly on a suspected leiomyoma and the patient’s pain is reproduced, the mass is likely the cause of the patient’s symptoms. Sonographically, leiomyomas are hypoechoic solid masses with posterior acoustic shadowing. On MRI, leiomyomas are well-circumscribed masses that are typically hypointense on T2-weighted images. Following hemorrhage, these masses can have a variety of T2 signal characteristics.17 Under the hormonal effects of pregnancy, leiomyomas may grow. If the mass enlarges a sufficient amount to outgrow its blood supply, “red degeneration” will ensue. Sonographic features seen in “red degeneration” include cystic components, an echogenic rim, and shadowing hyperechoic areas.15 On MRI, a leiomyoma that has undergone “red degeneration” will have increased T1 signal intensity and heterogeneously increased T2 signal intensity.2
Ovarian Torsion
Figure 12 Anechoic tubular structure, representing a fallopian tube (FTUBE), demonstrated on ultrasonography imaging. This structure is separate from the right ovary and uterus, consistent with a hydrosalpinx.
Pregnant patients have a 1% increased risk of ovarian torsion compared with nonpregnant patients. The majority of gravid patients with ovarian torsion are in the first half of their pregnancy. It is thought that the risk of ovarian torsion decreases in the second half of pregnancy because of the increased uterine size limiting the mobility of the ovaries. A torsed ovary may have a variety of appearances on ultrasonography depending on the acuity of torsion. In the more acute stages, the ovary may be enlarged with the parenchyma demonstrating a ground glass appearance (Fig. 13). The majority of follicles may be located peripherally. If the ovary is in an abnormal position, torsion should be considered. The
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“whirlpool sign” is the most specific sonographic feature in ovarian torsion.19 This refers to the appearance of vessels coiling in a twisted vascular pedicle on color Doppler. However, the “whirlpool sign” is not sensitive. Doppler spectral analysis can demonstrate arterial and venous flow, only arterial flow, or no flow in a torsed ovary.8 The possibility of multiple results on spectral analysis is due to differing degrees of torsion, possible intermittent torsion, and the dual arterial supply to the ovary. On MRI, a torsed ovary may be
Figure 15 MRI T2 half-Fourier acquisition single-shot turbo spin echo (HASTE) coronal image demonstrating fluid-filled, blind-ending tubular structure with filling defects, measuring 1.1 cm in diameter (arrow). Findings are consistent with appendicitis.
enlarged with high T2 signal intensity (Fig. 14). Occasionally, the ovary can be so edematous and high in T2 signal as to appear nearly cystic. In this situation, one should defer to ultrasonography results to determine whether the questioned structure is a cyst or an edematous ovary.
Pelvic Inflammatory Disease and Tubo-Ovarian Abscess Patients with pelvic inflammatory disease often present with nonspecific complaints, such as fever, pain, and vaginal discharge. Laboratory results can show leukocytosis. Sonographic examination may demonstrate an ovary with relatively increased color flow on Doppler analysis and increased pain with direct probe pressure when compared with the contralateral side. These are features of tubo-ovarian complex. An adnexal mass that is not identifiable as an ovary and is associated with pain is suggestive of a tubo-ovarian abscess in the correct clinical setting. It may be difficult to differentiate an abscess containing gas from bowel. In this situation, MRI can be helpful. Tubo-ovarian abscesses have thick walls, low T1 signal intensity, and high or heterogeneous T2 signal intensity.
Appendicitis
Figure 14 Coronal T2 weighted image (A) demonstrates a markedly enlarged ovary with peripheral follicles and increased stromal T2 signal intensity. Coronal T1 fat-saturated post contrast image (B) demonstrates complete absence of enhancement of the enlarged ovary. This is a surgically proven case of ovarian torsion. (Images courtesy of Dr. Shirley McCarthy at Yale New Haven Hospital.)
Appendicitis is a nongynecologic etiology for an adnexal mass. Pericecal fluid and an appendix dilated ⬎6 mm are features of appendicitis. The patient’s pain will correlate with the location of the appendix on sonographic examination. MRI can be helpful in cases where the appendix is not identified sonographically and appendicitis remains a clinical concern. On MRI, a dilated appendix may be seen with adjacent T2 increased signal intensity, signifying inflammatory changes (Fig. 15).
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Conclusions Ultrasonography and MRI are the main imaging modalities used to evaluate adnexal masses in pregnancy. Generally, ultrasonography is the initial modality of choice followed by MRI for complicated cases. Familiarity with differing roles of imaging modalities and radiologic appearances of adnexal masses in pregnancy is important for diagnosis and to help guide further surgical or medical management.
References 1. Adusumilli S, Hussain HK, Caoili EM, et al: MRI of sonographically indeterminate adnexal masses. AJR Am J Roentgenol 187:732-740, 2006 2. Telischak NA, Yeh BM, Joe BN, Westphalen AC, et al: MRI of adnexal masses in pregnancy. AJR Am J Roentgenol 191:364-370, 2008 3. Thornton JG, Wells M: Ovarian cysts in pregnancy: Does ultrasound make traditional management inappropriate? Obstet Gynecol 69:717720, 1987 4. Oto A, Ernst R, Jesse MK, et al: Magnetic resonance imaging of cystic adnexal lesions during pregnancy. Curr Probl Diagn Radiol 37:139144, 2008 5. Yoshihiro N, Kaisuke I, Takae S, et al: Ultrasonographic and clinical appearance of hemorrhagic ovarian cyst diagnosed by transvaginal scan. J Nippon Med Sch 70:243-249, 2003 6. Patel MD, Feldstein VA, Chen DC, et al: Endometriomas: Diagnostic performance of US. Radiology 210:739-745, 1999 7. Outwater E, Schiebler ML, Owen RS, et al: Characterization of hemorrhagic adnexal lesions with MR imaging: Blinded reader study. Radiology 186:489-494, 1993
M. Yacobozzi, D. Nguyen, and D. Rakita 8. Glanc P, Salem S, Farine D: Adnexal masses in the pregnant patient: A diagnostic and management challenge. Ultrasound Q 24:225-240, 2008 9. Kosary CL. Chapter 16. Cancer of the Ovary. SEER Survival Monograph. Available at: http://www.Seer.cancer.gov/publications/survival/ surv_ovary.pdf. Accessed: June 2011 10. Giuntoli RL, Vang RS, Bristow RE: Evaluation and management of adnexal masses during pregnancy. Clin Obstet Gynecol 49:492-505, 2006 11. Ayhan A, Bukulmez O, Genc C, et al: Mature cystic teratomas of the ovary: Case series from one institution over 34 years. Eur J Obstet Gynecol Reprod Biol 88:153-157, 2000 12. Stevens SK, Hricak H, Campos Z: Teratomas versus cystic hemorrhagic adnexal lesions: Differentiation with pronton-selective fat-saturation MR Imaging. Radiology 186:481-488, 1993 13. Imaoka I, Wada A, Wada K, et al: Developing an MR imaging strategy for diagnosis of ovarian masses. Radiology 26:1431-1449, 2006 14. Brown DL, Dudiak KM, Laing FC: Adnexal masses: US characterization and reporting. Radiology 254:342-354, 2010 15. Tanaka YO, Nishida M, Kurosaki Y, et al: Differential diagnosis of gynaecological “stained glass” tumours on MRI. Br J Radiol 72:414420, 1999 16. Ha HK, Baek SY, Kim SH, et al: Krukenberg’s tumor of the ovary: MR imaging features. AJR Am J Roentgenol 164:1435-1439, 1995 17. Chiang G, Levine D: Imaging of adnexal masses in pregnancy. J Ultrasound Med 23:805-819, 2004 18. Patel MD, Acord DL, Young SW: Likelihood ratio of sonographic findings in discriminating hydrosalpinx from other adnexal masses. AJR Am J Roentgenol 186:1033-1038, 2006 19. Vijayaraghavan SB: Sonographic whirlpool sign in ovarian torsion. J Ultrasound Med 23:1643-1649, 2004
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dnexal masses are incidentally found on routine screening examinations in pregnancy. With the technologic advances in ultrasonography, the incidence of adnexal masses in gravid patients has increased. It is essential to recognize the sonographic features of particular adnexal masses seen in the pregnant patient to help establish a diagnosis and guide clinical or surgical management. In addition, understanding the role of magnetic resonance imaging (MRI) in the diagnosis of adnexal masses and the appearance of various adnexal masses on MRI is imperative.
Ultrasonography and MRI Techniques Ultrasonography is the first-line imaging modality used for evaluating adnexal masses during pregnancy. Ideally, both transabdominal and transvaginal techniques are used. Twodimensional ultrasonography is typically used, but in certain cases, 3-dimensional ultrasonography may be valuable. Doppler ultrasonography is a critical tool in the characterization of masses. For example, the presence of color flow within a septum or solid component of the mass may increase suspicion for malignancy. Sonography also serves as a useful modality for following the progression or regression of adnexal masses. Department of Radiology, Tufts School of Medicine, Baystate Medical Center, Springfield, MA. Address reprint requests to Margaret Yacobozzi, MD, Department of Radiology, Baystate Medical Center, 759 Chestnut Street, Springfield, MA 01199. E-mail: [email protected]
0887-2171/$-see front matter © 2012 Published by Elsevier Inc. doi:10.1053/j.sult.2011.10.004
For the up to 20% of sonographically indeterminate adnexal lesions, MRI is used as a second-line imaging modality.1 MRI is useful in evaluating adnexal masses that are too large to be accurately evaluated by ultrasonography. Specific MRI techniques are used to obtain diagnostic images. Patients should fast for 4 hours before an MRI examination to limit artifact from bowel peristalsis. Generally, the patient should be scanned in the supine position. However, it may be necessary to scan in the left lateral decubitus position in the later stages of pregnancy to avoid inferior vena cava compression. A body array coil placed over the pelvis is used. Rapid imaging is performed with multislice-spoiled gradient echo for T1 images and single-shot rapid acquisition relaxation-enhanced sequences for T2 images. Image acquisition can be obtained during a maternal breath-hold, respiratory triggered, or free breathing.2 Before performing an MRI on pregnant patients, the potential risks must be explained. There is no evidence to prove that MRI is safe with respect to the fetus. However, no teratogenic/carcinogenic effects have been documented. A balance must be found between the necessity of information that will be gained by performing an MRI versus the undocumented safety of MRI during pregnancy. It is preferable that MRI not be performed before organogenesis. Gadolinium-based contrast is a pregnancy category C drug, with animal studies indicating increased skeletal malformations in offspring of exposed animals. Gadolinium-based contrast can enter the fetal circulation through the placenta and then be excreted by the fetal kidneys, leading to the contrast agent accumulating in the amniotic fluid. 55
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Nonneoplastic Lesions Pregnancy-Associated Cysts Pregnancy-associated cysts include corpus luteum, hemorrhagic, and follicular. Many of the adnexal cystic masses will resolve spontaneously. In fact, it has been reported that 90%100% of cystic masses ⬍5 cm in pregnant patients resolve spontaneously.3 Larger cysts, even when benign, can be associated with torsion, rupture, and labor obstruction. These larger cysts require monitoring and possibly surgery. Corpus luteum cysts form after ovulation and persist for 5-9 weeks of pregnancy. These cysts produce progesterone before the placenta and are essential to maintenance of the pregnancy. Usual resolution of the corpus luteum cyst occurs at 8 weeks. On ultrasonography, the appearance of corpus luteum cysts varies in part because of varying components of hemorrhage. They may appear to be simple or complex. Characteristically, on Doppler ultrasonography, a peripheral ring of color is demonstrated, called a “ring of fire” (Fig. 1). The size of these cysts ranges from 2.5 to 6 cm.4 The walls of corpus luteum cysts are thicker than follicular cysts. The MRI appearance of corpus luteal cysts also varies because of the differing components contained within the cyst. Usually, increased T1 signal intensity is demonstrated with correlating low T2 signal intensity. The appearance of hemorrhagic cysts also differs because of varying stages of clot evolution. Hemorrhagic cysts are generally anechoic masses with internal hypoechoic material and increased sound through transmission. In acute hemorrhage, a hemorrhagic cyst may be echogenic on sonography. A specific sonographic feature of hemorrhagic cysts includes a reticular pattern of blood products. Later in the evolution of hemorrhagic cysts, solid and cystic components can be dis-
Figure 2 Ultrasonography of a normal ovary demonstrates multiple anechoic follicles, all measuring ⬍2 cm.
tinguished, with the solid component representing a retracting clot.5 The MRI appearance of a hemorrhagic cyst is again variable, typically manifested by uniform or dependently layering high T1 and low T2 signal. MRI may not always be conclusive in the diagnosis. A follicle is a simple functional cyst influenced by hormonal changes. A follicular cyst can be seen when a follicle does not spontaneously regress. By definition, a mature follicle is ⬍2 cm in diameter, whereas follicular cysts are ⬎2.5 cm. These cysts are anechoic on sonography and homogeneously T2 bright on MRI (Fig. 2).
Endometriomas
Figure 1 Anechoic corpus luteum cyst demonstrates peripheral color flow on Doppler ultrasonography, referred to as a “ring of fire.” (Color version of figure is available online.)
The prevalence of endometriomas is 3%-10%.4 Although many of these regress, some remain stable for months or can even enlarge. Up to 95% of endometriomas demonstrate diffuse homogenous low-level internal echoes.6 However, endometriomas can vary in appearance from largely cystic to solid, and their appearance can occasionally mirror that of hemorrhagic cysts. Associated calcifications can be seen, which are usually large enough to exhibit acoustic shadowing. Hemorrhagic products account for high T1 and a low T2 signal on MRI (Fig. 3). Endometriomas can be homogeneously low signal on T2-weighted images or can exhibit T2 “shading,” which is a gradual transition from high T2 to low T2 signal. Identifying fibrous bands of adhesions in the pelvis on MRI strongly supports the diagnosis of endometriosis. It has been reported that MRI is 68% sensitive and 83% specific in diagnosing endometriotic cysts from other hemorrhagic lesions.7 Unique to pregnancy and its progestational effects, ectopic decidualization of the wall of an endometrioma may be seen. Sonography may demonstrate solid vascular nodules within
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Germ Cell Tumors
Figure 3 Axial T2 (A) and fat-suppressed T1 (B) images demonstrating an intermediate T2 and high T1 signal mass in the left adnexa (arrow). This is an example of an endometrioma.
the wall of an endometrioma, mirroring the vascular decidual lining of the uterus. This appearance may raise concerns for malignancy, and an MRI may be done for further investigation. In ectopic decidualization, the solid vascular component of the endometrioma will resemble the MRI appearance of the uterine decidual lining in early pregnancy.2
Neoplasms Cancer and pregnancy have a rate of association of 1/1000 live births.8 Twelve and a half percent of ovarian cancers are seen in women ⬍40 years old.9 Six percent of adnexal masses excised during pregnancy were found to be malignant.10 Evaluating the gravid patient for ovarian cancer has added complications. Tumor markers that can be used in nonpregnant patients may already be elevated, as in cancer antigen 125. This makes imaging even more important in the workup of adnexal masses in the pregnant patient.
Teratomas are included within the category of germ cell tumors. After 16 weeks of gestation, teratomas are the most common adnexal cystic lesion. Teratomas may be bilateral in approximately 10%-13.2% of cases.11 These lesions have an approximately 2% rate of malignant transformation, which will most commonly be of the invasive squamous carcinoma type. Pregnancy complications secondary to these lesions are uncommon when masses are ⬍6 cm. On ultrasonography, mature cystic teratomas, or dermoids, have several characteristic features. Hyperechoic nodules with distal acoustic shadowing may be seen, referred to as a “dermoid plug.” “Tip of the iceberg phenomenon” occurs when echogenic areas of the teratoma attenuate the ultrasonography beam. This causes the back wall of the cyst to be obscured by acoustic shadowing. Hair and sebum in teratomas cause hyperechoic lines and dots, leading to the “dermoid mesh” pattern. Less commonly, a fluid-fluid level may be seen in which the nondependent portion is hyperechoic fat and the dependent layer is more hypoechoic fluid. Teratomas may contain echogenic floating balls (representing fat) within a cystic structure. MRI can be useful when the sonographic appearance is nonspecific. Mature cystic teratomas demonstrate the chemical shift artifact at least 62% of the time12 (Fig. 4). Selective chemical fat-suppression technique can be used to distinguish cystic teratomas from hemorrhagic adnexal processes with a sensitivity of 92%.12 Dermoids are high intensity on T1 and T2 sequences. Dysgerminomas also fall within the spectrum of germ cell tumors. Excluding epithelial tumors of low malignant potential, dysgerminomas are the most common invasive malignant neoplasm in pregnancy. These masses do carry a good prognosis, as they are sensitive to chemotherapy and radiation. On sonography, these lesions appear as a solid mass. However, if there is necrosis, the mass may contain anechoic components. On MRI, dysgerminomas demonstrate increased signal intensity on T2-weighted images, with presence of T2 hypointense septations.13
Fibromas Fibromas are included in the category of sex cord-stromal tumors, which account for one-fifth of ovarian malignancies found during pregnancy. On ultrasonography, these masses appear hypoechoic and solid, although they may contain cystic components (Fig. 5). In approximately 18%-52% of cases, they demonstrate acoustic shadowing, similar to uterine fibroids.14 In fact, it may be difficult to separate fibromas from uterine fibroids when the fibroma grows as an exophytic ovarian mass. When detected by MRI, these masses demonstrate characteristic low T2 intensity because of the fibrocollagenous stroma.13 Fibromas are intermediate signal on T1-weighted images (Fig. 6). Granulosa cell tumors are also included within the spectrum of sex cord-stromal tumors and rarely occur in pregnancy. Typically, granulosa cell tumors present at stage I, and the patient can be cured surgically. They can be solid or be
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Figure 4 Large right adnexal mass with a fat–fluid level. (A) Fat-saturated T2-weighted image demonstrates bulk fat suppression, whereas (B) opposed phase images demonstrate signal loss of the fat mixed with fluid. This is characteristic of a dermoid.
multilocular with solid components. Intratumoral hemorrhage can occasionally be demonstrated on MRI.
Ovarian Epithelial Neoplasms Up to one-half of ovarian malignancies in pregnancy are ovarian epithelial neoplasms. These neoplasms include cystadenomas, cystadenocarcinomas, and tumors of low malignant potential.
Cystadenomas Cystadenomas account for 40%-50% of benign ovarian neoplasms in the general population, with serous cystadenomas being more common than the mucinous type. On ultrasonography, serous cystadenomas may resemble a simple cyst that is larger than a typical functional cyst. Thin septa-
tions or, occasionally, papillary projections may also be present. When a serous cystadenoma is suspected, it is of increased importance to evaluate the contralateral ovary; bilaterality is seen in up to 20% of cases.8 On MRI, serous cystadenomas have the expected appearance of a cystic lesion with high T2 and low T1 signal intensities. The occurrence of malignant transformation of serous cystadenomas is not substantiated, but is thought to be uncommon if it does occur. The possibility of a simple cyst-like lesion having malignant potential is the impetus to follow-up simple cysts. However, lack of interval growth on a short-term follow-up examination is not necessarily adequate to exclude cystadenomas, as they may be slow growing. Mucinous cystadenomas are multilocular cysts containing fluid of various viscosities.13 Reflecting this, sonographic im-
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59 mural wall nodules and papillary projections. It is not always possible to discriminate between tumors of low malignant potential and other ovarian epithelial neoplasms. For example, mucinous cystic tumor of borderline malignancy does not have distinguishing features from a mucinous cystadenoma.
Metastatic Ovarian Tumors Ten percent of ovarian cancers are secondary to metastatic disease. However, metastatic ovarian tumors are less com-
Figure 5 Gray-scale ultrasonography image demonstrating a hypoechoic solid left ovarian mass with acoustic shadowing. This was a biopsy-proven ovarian fibroma.
ages of these lesions demonstrate low-level internal echoes with multiple thin septae (Fig. 7). As in serous cystadenomas, the mucinous type can contain papillary projections. However, unlike the serous type, mucinous cystadenomas are rarely unilocular. Because of overlapping appearances, serous versus mucinous cystadenomas cannot be distinguished by ultrasonography. On MRI, the loculi of mucinous cystadenomas appear as varying intensities on T1and T2-weighted imaging because of the varying viscosity of components. This is referred to as a “stained glass” appearance.15
Cystadenocarcinomas Serous and mucinous cystadenocarcinomas are both multilocular cystic masses with features of malignancy not seen in cystadenomas. These features include thicker septations, papillary projections ⬎3 mm in size, and irregular walls (Figs. 8 and 9). Mural and septal nodules with color flow on Doppler analysis are also seen in cystadenocarcinomas.13
Tumors of Low Malignant Potential Tumors of low malignant potential are masses with histological features of malignancy without invasion into the ovarian stroma. These tumors are most common in women of childbearing age. On ultrasonography, tumors of low malignant potential may demonstrate an “ovarian crescent sign,” which is when a rim of normal-appearing ovarian tissue can be visualized adjacent to the tumor. When this sign is present, it argues against invasion of the tumor into the ovary. Features of malignancy are seen in these lesions, including vascular
Figure 6 Magnetic resonance image (MRI) of the same patient as in Fig. 4. Left ovarian fibroma (arrow) is low intensity on T2weighted imaging (A) and intermediate to low signal on T1weighted imaging (B).
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Figure 7 Ultrasonography image of a large anechoic cystic structure with a daughter cyst (within calibers). This was a biopsy-proven mucinous cystadenoma.
monly seen in the pregnant population. The most common primary tumors to metastasize to the ovaries are breast, intestinal, and gastric cancers, as these neoplasms spread via blood vessels and lymphatics. There are similarities in the appearances between primary and secondary ovarian tumors. However, bilaterality is significantly greater in metastatic tumors. Ovarian tumors are
Figure 9 Coronal MRI T1-weighted precontrast image (A) and T1 fat-saturated postcontrast image (B) showing a complex cystic mass with enhancing solid components (arrow). This was a biopsyproven cystadenocarcinoma.
Figure 8 Ultrasonography demonstrating a complex right adnexal mass with vascular solid components and septae (arrowhead). This was a biopsy-proven cystadenocarcinoma. (Color version of figure is available online.)
usually solid, but also may appear as cystic masses. It is rare, however, for an ovarian metastasis to present as a thin-walled simple cyst. Krukenberg tumors are solid bilateral metastatic ovarian malignancies that arise from signet-ring cell carcinomas, most commonly gastric in origin. These tumors may have significant collagen formation, leading to hypointensity on T2 images. Alternatively, Krukenberg tumors may demonstrate considerable edema, correlating with hyperintensity on T2-weighted images.16
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Pregnancy-Related Lesions Hyperstimulated Ovaries Hyperstimulated ovaries are primarily seen in patients after ovulation induction. On ultrasonography, ovaries are enlarged and demonstrate the characteristic “spoke wheel” appearance.8 This refers to central echogenic ovarian stoma with peripheral ovarian cysts. Ovarian hyperstimulation syndrome is categorized into mild, moderate, or severe based on the amount of ovarian enlargement and patient weight gain. This condition spontaneously resolves in 90% of patients.17 Patients with hyperstimulated ovaries are at increased risk for torsion secondary to ovarian enlargement.
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Theca Lutein Cysts Theca lutein cysts occur with a normal ovarian response to elevated levels of hCG. Therefore, conditions that increase hCG levels, such as gestation trophoblastic disease, multiple pregnancies, and gonadotrophin therapy for infertility, place patients at risk for this condition. Sonographically, the ovaries are enlarged and contain multiple cysts, analogous to hyperreactio luteinalis. On MRI, bilateral ovarian enlargement secondary to multiple thin-walled cysts is seen. Because of ovarian enlargement, an increased risk of torsion exists. Following treatment of the underlying cause of elevated hCG, ovaries return to baseline.
Luteoma of Pregnancy Hyperreactio Luteinalis Hyperreactio luteinalis occurs when patients have increased sensitivity to circulating hCG. Hyperreactio luteinalis typically manifests in the third trimester of pregnancy. Clinically, patients may be asymptomatic or may present with abdominal pain and distention, abnormal liver function tests, respiratory difficulties, or hirsutism.8 Maternal virilization can occur in 14%-25% of women with hyperreactio luteinalis. These patients, by definition, have not undergone ovulation induction. Patients with hyperandrogenism, such as in polycystic ovarian syndrome, are at risk for developing this condition. On both ultrasonography and MRI, the ovaries are enlarged and have multiple peripheral cysts, similar to hyperstimulated ovaries (Fig. 10). However, there is relatively less ovarian enlargement. Spontaneous regression of cysts is seen after delivery.
Luteoma of pregnancy occurs when proliferation of luteinized stromal cells replaces the normal ovarian parenchyma. This occurs under the influence of hCG. The proliferated stromal cells are capable of producing androgens, which may cause maternal virilization as well as virilization of the female fetus. On ultrasonography, luteomas appear as heterogeneous, predominantly hypoechoic masses. Considerable vascularity may be demonstrated on Doppler analysis. Overall, however, the appearance of luteomas is nonspecific, and the diagnosis must be based on both clinical and radiologic findings. The condition will regress along with decreasing androgen levels.
Paraovarian Masses Paraovarian lesions are almost always of benign etiology. Therefore, the ability to distinguish ovarian from paraovarian locations is of value. This can be done by attempting to separate the lesion from the ovary with direct probe pressure during a transvaginal examination. MRI may be helpful to define a lesion as extraovarian by identifying a normal ovary separate from the questioned structure.
Cysts Paraovarian cysts are typically located in the mesosalpinx between the fallopian tube and ovary. These cysts usually range between 1 and 2 cm in size. On imaging, paraovarian cysts demonstrate the same characteristics seen in cysts throughout the body; they are thin-walled anechoic structures on ultrasonography and T2 hyperintense and T1 hypointense on MRI (Fig. 11). Paraovarian cysts are common and are of no clinical significance.
Hydrosalpinx
Figure 10 Ultrasonography images from a pregnant female demonstrating enlargement of the ovary with multiple peripheral anechoic cysts (one demarcated with calibers). This patient was diagnosed with hyperreactio luteinalis by her obstetrician.
Hydrosalpinx is dilatation of the fallopian tube with fluid. Dilatation occurs following distal obstruction of the fallopian tube by adhesions. Common causes of hydrosalpinx are salpingitis and pelvic endometriosis. Hydrosalpinx appears as a tubular anechoic cystic structure that remains unchanged throughout pregnancy (Fig. 12). The most specific finding on ultrasonography is the “waist sign,” indicating that there are 2 diametrically opposed indentations in the wall of the fallopian tube.18 In chronic hydrosalpinx, the “string of beads sign” may be seen. This refers to small nodules along the wall of the fallo-
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Figure 13 Ultrasonography in a patient with pelvic pain demonstrates an enlarged ovary with a ground glass appearance. This was surgically proven to represent a torsed ovary. Figure 11 Ultrasonography examination reveals an anechoic cyst (arrow) between the uterus and the ovary, characteristic of a paraovarian cyst.
pian tube, correlating with thickened folds. MRI may be helpful in cases when it is unclear whether the cystic structure seen on ultrasonography is definitely separate from the ovary.
Leiomyomas Leiomyomas are the most common solid adnexal mass found in pregnancy. Although the most common location of a leio-
myoma is the uterine body, these masses may simulate an ovarian mass when pedunculated. Clinically, patients with leiomyomas may present with acute pain because of degeneration, hemorrhage, or torsion of the mass. Ultrasonography examinations can be beneficial in diagnosing patients because of its real-time capability. If pressure is applied by an ultrasonography probe directly on a suspected leiomyoma and the patient’s pain is reproduced, the mass is likely the cause of the patient’s symptoms. Sonographically, leiomyomas are hypoechoic solid masses with posterior acoustic shadowing. On MRI, leiomyomas are well-circumscribed masses that are typically hypointense on T2-weighted images. Following hemorrhage, these masses can have a variety of T2 signal characteristics.17 Under the hormonal effects of pregnancy, leiomyomas may grow. If the mass enlarges a sufficient amount to outgrow its blood supply, “red degeneration” will ensue. Sonographic features seen in “red degeneration” include cystic components, an echogenic rim, and shadowing hyperechoic areas.15 On MRI, a leiomyoma that has undergone “red degeneration” will have increased T1 signal intensity and heterogeneously increased T2 signal intensity.2
Ovarian Torsion
Figure 12 Anechoic tubular structure, representing a fallopian tube (FTUBE), demonstrated on ultrasonography imaging. This structure is separate from the right ovary and uterus, consistent with a hydrosalpinx.
Pregnant patients have a 1% increased risk of ovarian torsion compared with nonpregnant patients. The majority of gravid patients with ovarian torsion are in the first half of their pregnancy. It is thought that the risk of ovarian torsion decreases in the second half of pregnancy because of the increased uterine size limiting the mobility of the ovaries. A torsed ovary may have a variety of appearances on ultrasonography depending on the acuity of torsion. In the more acute stages, the ovary may be enlarged with the parenchyma demonstrating a ground glass appearance (Fig. 13). The majority of follicles may be located peripherally. If the ovary is in an abnormal position, torsion should be considered. The
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“whirlpool sign” is the most specific sonographic feature in ovarian torsion.19 This refers to the appearance of vessels coiling in a twisted vascular pedicle on color Doppler. However, the “whirlpool sign” is not sensitive. Doppler spectral analysis can demonstrate arterial and venous flow, only arterial flow, or no flow in a torsed ovary.8 The possibility of multiple results on spectral analysis is due to differing degrees of torsion, possible intermittent torsion, and the dual arterial supply to the ovary. On MRI, a torsed ovary may be
Figure 15 MRI T2 half-Fourier acquisition single-shot turbo spin echo (HASTE) coronal image demonstrating fluid-filled, blind-ending tubular structure with filling defects, measuring 1.1 cm in diameter (arrow). Findings are consistent with appendicitis.
enlarged with high T2 signal intensity (Fig. 14). Occasionally, the ovary can be so edematous and high in T2 signal as to appear nearly cystic. In this situation, one should defer to ultrasonography results to determine whether the questioned structure is a cyst or an edematous ovary.
Pelvic Inflammatory Disease and Tubo-Ovarian Abscess Patients with pelvic inflammatory disease often present with nonspecific complaints, such as fever, pain, and vaginal discharge. Laboratory results can show leukocytosis. Sonographic examination may demonstrate an ovary with relatively increased color flow on Doppler analysis and increased pain with direct probe pressure when compared with the contralateral side. These are features of tubo-ovarian complex. An adnexal mass that is not identifiable as an ovary and is associated with pain is suggestive of a tubo-ovarian abscess in the correct clinical setting. It may be difficult to differentiate an abscess containing gas from bowel. In this situation, MRI can be helpful. Tubo-ovarian abscesses have thick walls, low T1 signal intensity, and high or heterogeneous T2 signal intensity.
Appendicitis
Figure 14 Coronal T2 weighted image (A) demonstrates a markedly enlarged ovary with peripheral follicles and increased stromal T2 signal intensity. Coronal T1 fat-saturated post contrast image (B) demonstrates complete absence of enhancement of the enlarged ovary. This is a surgically proven case of ovarian torsion. (Images courtesy of Dr. Shirley McCarthy at Yale New Haven Hospital.)
Appendicitis is a nongynecologic etiology for an adnexal mass. Pericecal fluid and an appendix dilated ⬎6 mm are features of appendicitis. The patient’s pain will correlate with the location of the appendix on sonographic examination. MRI can be helpful in cases where the appendix is not identified sonographically and appendicitis remains a clinical concern. On MRI, a dilated appendix may be seen with adjacent T2 increased signal intensity, signifying inflammatory changes (Fig. 15).
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Conclusions Ultrasonography and MRI are the main imaging modalities used to evaluate adnexal masses in pregnancy. Generally, ultrasonography is the initial modality of choice followed by MRI for complicated cases. Familiarity with differing roles of imaging modalities and radiologic appearances of adnexal masses in pregnancy is important for diagnosis and to help guide further surgical or medical management.
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M. Yacobozzi, D. Nguyen, and D. Rakita 8. Glanc P, Salem S, Farine D: Adnexal masses in the pregnant patient: A diagnostic and management challenge. Ultrasound Q 24:225-240, 2008 9. Kosary CL. Chapter 16. Cancer of the Ovary. SEER Survival Monograph. Available at: http://www.Seer.cancer.gov/publications/survival/ surv_ovary.pdf. Accessed: June 2011 10. Giuntoli RL, Vang RS, Bristow RE: Evaluation and management of adnexal masses during pregnancy. Clin Obstet Gynecol 49:492-505, 2006 11. Ayhan A, Bukulmez O, Genc C, et al: Mature cystic teratomas of the ovary: Case series from one institution over 34 years. Eur J Obstet Gynecol Reprod Biol 88:153-157, 2000 12. Stevens SK, Hricak H, Campos Z: Teratomas versus cystic hemorrhagic adnexal lesions: Differentiation with pronton-selective fat-saturation MR Imaging. Radiology 186:481-488, 1993 13. Imaoka I, Wada A, Wada K, et al: Developing an MR imaging strategy for diagnosis of ovarian masses. Radiology 26:1431-1449, 2006 14. Brown DL, Dudiak KM, Laing FC: Adnexal masses: US characterization and reporting. Radiology 254:342-354, 2010 15. Tanaka YO, Nishida M, Kurosaki Y, et al: Differential diagnosis of gynaecological “stained glass” tumours on MRI. Br J Radiol 72:414420, 1999 16. Ha HK, Baek SY, Kim SH, et al: Krukenberg’s tumor of the ovary: MR imaging features. AJR Am J Roentgenol 164:1435-1439, 1995 17. Chiang G, Levine D: Imaging of adnexal masses in pregnancy. J Ultrasound Med 23:805-819, 2004 18. Patel MD, Acord DL, Young SW: Likelihood ratio of sonographic findings in discriminating hydrosalpinx from other adnexal masses. AJR Am J Roentgenol 186:1033-1038, 2006 19. Vijayaraghavan SB: Sonographic whirlpool sign in ovarian torsion. J Ultrasound Med 23:1643-1649, 2004