First-Trimester Ultrasound: A Comprehensive Guide

21. Sonography of Pelvic Masses Associated with Early Pregnancy

Chelsea R. Samson1, 2  Rochelle F. Andreotti3, 4  Rifat A. Wahab5, 6  Glynis Sacks  and Arthur C. Fleischer 

(1)

Vanderbilt University Medical Center, Vanderbilt University School of Medicine, 2215 Garland Ave., Nashville, TN 37232, USA

(2)

1920 Adelicia St., #408, Nashville, TN 37212, USA

(3)

Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, CCC-1118 Medical Center North, 1161 21st Ave South, Nashville, TN 37232, USA

(4)

2115 Sharondale Dr, Nashville, TN 37215, USA

(5)

Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1161 21st Ave South, Nashville, TN 37232, USA

(6)

3111 Long Blvd Apt. 3107, Nashville, TN 37203, USA

(7)

Department of Radiology, Center for Women’s Imaging, Vanderbilt University Medical Center, 3319 West End Ave, Suite 650, Nashville, TN 37203, USA

(8)

Department of Radiology, Vanderbilt University Medical Center, 1161 21st Avenue, Nashville, TN 37232, USA

Chelsea R. Samson

Email: chelsea.r.samson@vanderbilt.edu

Rochelle F. Andreotti

Email: rochelle.f.andreotti@vanderbilt.edu

Rifat A. Wahab

Email: Rifat.a.Wahab@Vanderbilt.edu

Glynis Sacks

Email: glynis.sacks@vanderbilt.edu

Arthur C. Fleischer (Corresponding author)

Email: arthur.fleischer@vanderbilt.edu

Keywords

First-trimester sonographyIncidental findingsLeiomyomaFibroidCorpus luteumLuteum cystEndometriomaDermoid cystTeratomaOvarian cancerAdnexal mass

Clinical Implications

First-trimester sonography allows for visualization of pelvic anatomy before the expanding uterus shifts and conceals neighboring structures. For many young pregnant women, this study may be their first radiologic exam. Previously asymptomatic or small pathology hidden to palpation reveals itself to sonography and impacts subsequent clinical decisions. The sonographic findings aid in the development of differential diagnoses and are highly specific for malignancy. Incidental masses may require prompt treatment, alter the labor and delivery plan, or necessitate further imaging. The most recent joint guidelines on obstetrical sonography published by the American College of Radiology appropriately reflect the need for a comprehensive first-trimester sonogram that includes the “uterus, cervix, adnexa, and cul-de-sac region” along with the gestational contents [1]. This ensures that any poorly localized symptoms are not mistaken for the normal discomforts of pregnancy.

Undetected non-obstetrical abnormalities can cause significant complications despite their frequently benign cytology. The hormonal effects of pregnancy and increasing uterine girth can cause leiomyoma to enlarge, cysts to rupture, adnexal masses to undergo torsion, and cancers to grow. Early identification of abnormalities in the first trimester facilitates surgical treatment, if necessary, during the second trimester. At that time, risks of spontaneous abortion and preterm labor are lowest and surgical exposure remains adequate. Though smaller incidental masses with benign sonographic characteristics are amenable to observation [2], invasive intervention is typically initiated for those that are larger (usually greater than 7 cm in diameter), undergoing torsion, and/or suspicious for malignancy. Sonography can be used to accurately differentiate between the architectural patterns of benign and malignant masses and to determine which would be associated with an increased risk of ovarian torsion [36].

Techniques

Identification of incidental findings on transabdominal obstetrical sonography, inability to visualize the adnexa or cervix, or examination of an obese patient may obligate further study via the transvaginal approach [13]. This technique is generally quite tolerable for the patient, eschews fetal radiation, and avoids signal attenuation by subcutaneous tissues. In addition, it provides higher resolution views of pelvic pathology owing to probes of higher frequency that contain anatomy of interest within a shallower focal length than commonly used transabdominal probes.

Three-dimensional sonography has proven particularly beneficial in imaging of the uterus and adnexa. Transvaginal probes have been adapted to collect many consecutive two-dimensional images throughout a region of interest while the probe is held stationary. This creates a user-independent, lifelike volume that can be manipulated and reconstructed in the coronal plane. This plane cannot usually be obtained by two-dimensional transvaginal sonography, but can add additional information that is essential when evaluating uterine anomalies.

Both two-dimensional and three-dimensional sonography can include color Doppler sonography. Evaluation of incidental findings must consider the local vascular tree, though physiologic hemodynamic changes of pregnancy can complicate analysis. In general, disorganized vasculature with low resistance and high flow is characteristic of ominous diagnoses [3]. Early in the first trimester, embryos are most susceptible to external teratogens, which theoretically include the thermal and mechanical energy generated by pulsed spectral Doppler, in particular [7]. Thus, the American Institute of Ultrasound in Medicine recommends utilization of Doppler studies that include the embryo or fetus only when there is clear diagnostic benefit while minimizing embryonic exposure time and intensity [8].

Uterine Masses

Fibroids

Leiomyomas, benign smooth muscle tumors commonly referred to as “fibroids,” are the most prevalent gynecologic affliction of the gravid and non-gravid female. They are commonly found incidentally on first-trimester sonography [45]. These persistent, round, well-defined masses are iso- or slightly hypoechoic compared to the surrounding myometrium and demonstrate peripheral vascularity by color Doppler sonography. They may contain shadowing calcifications and areas of cystic change when undergoing degeneration (Fig. 21.1).

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Fig. 21.1

Subserosal fibroid. Transvaginal grayscale transverse image of the uterus demonstrates a round heterogeneous mass, measuring 0.51 cm wide (+), projecting beyond the contour of the uterus. The gestational sac with embryo is noted

Fibroids are highly sensitive to estrogen, which can promote their growth and maturation in the first trimester. They may even grow so large as to overwhelm their blood supply, resulting in painful degenerative changes including changing echogenicity and loss of clear circumferential vascularity. The loss of blood supply may result in various types of degeneration: hyaline or myxoid degeneration, calcification, cystic degeneration, or red (hemorrhagic) degeneration. Red, or carneous, degeneration is a hemorrhagic infarction secondary to venous thrombosis within the periphery of the tumor or rupture of intratumoral arteries. It is of upmost importance to utilize sonography early in pregnancy to identify those fibroids that would be clinically significant due to their size and location. Submucosal fibroids may increase the risk of early pregnancy loss. If first-trimester miscarriage is eluded, these benign masses can have significant detrimental ramifications that are not realized until later trimesters. Mass effect and disruption of placental implantation caused by large fibroids compete with fetal growth and can obstruct fetal and placental delivery if located within the lower uterine segment [59]. Increased pressure above a low-lying fibroid during labor increases the risk of uterine rupture and fetal mortality. Despite these complications, intervention is usually not necessary or commonly pursued until the postpartum period.

The pervasive fibroid can present unexpected challenges for the medical imaging specialist. Subserosal-type fibroids pushed close to an ovary by the gravid uterus can be difficult to differentiate from a solid ovarian mass. Degenerative changes in such a fibroid may further complicate diagnosis. Imaging a separate ovary, often better differentiated on three-dimensional sonography, will exclude an ovarian mass. Color Doppler may also be helpful in delineating blood flow that connects the uterus and fibroid. If ultrasound is inconclusive, further imaging with MRI may be required.

Adnexal Masses

Traditional management of adnexal masses during pregnancy has been surgical, but with surgeries come both fetal and maternal risks. The goal of ultrasound evaluation is to determine when conservative management with observation is appropriate. Simple cysts of any size and classic-appearing hemorrhagic cysts are highly unlikely to be malignant lesions in menstruating females. Follow-up or further evaluation is recommended only when the size is greater than 5 cm. Reports have shown a high accuracy of ultrasound for determination of malignant potential. Schmeler et al. and Kumari et al. reported correct diagnosis of malignancy in all pregnant patients studied presenting with incidental adnexal masses [610].

Corpus Luteum

A retrospective review of sonography performed on over 18,000 pregnant patients identified a 2.3 % prevalence of adnexal masses; the majority were small (<5 cm) simple cysts that were without complication during the pregnancies [11]. The majority of these cysts likely begin as corpora lutea: the most commonly encountered cystic adnexal mass during pregnancy [4]. Corpora lutea form after fertilization of an expulsed ovum from an ovarian follicle. They endure to produce progesterone and maintain the early pregnancy. Fluid-filled with smooth, thick walls, they grow to a maximum diameter at the end of the first trimester. The decreasing functionality of the corpus luteum as the placenta assumes that an endocrinologic role is reflected sonographically by its serially shrinking size by the second trimester.

The lifetime of the corpus luteum in a pregnant woman is much longer than during a normal menstrual cycle and it has more opportunity to grow; thus, complications such as rupture, torsion, and hemorrhage can more commonly occur in a pregnant patient (Fig. 21.2a, b) However, intervention and further imaging are otherwise unnecessary for this physiologic incidental finding and should not be pursued during the first trimester when progesterone production is essential.

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Fig. 21.2

Corpus luteum. Grayscale transvaginal (a) transverse and (b) sagittal images of the ovary demonstrate a predominately anechoic cyst containing hypoechoic dependent debris representing old blood products

Corpus Luteum Cysts

A persistent corpus luteum can seal externally within the ovary and continue to collect fluid within, forming a unilocular corpus luteum cyst. Because the cyst contains fluid, it is anechoic with enhanced through-transmission, though it may exhibit thin lacelike echogenic septae if it persists into the second trimester and is filled with blood [5]. The size of the cyst is a strong predictor of its ability to spontaneously regress, with almost all cysts under 5 cm in diameter resolving completely without intervention [12]. The most recent guidelines (2010) for non-gravid women from the Society of Radiologists in Ultrasound do not recommend follow-up sonography for simple cysts smaller than 5 cm, whereas yearly sonography of larger cysts should be considered, despite low malignant potential [13]. Standard scheduling of obstetric ultrasounds offers the opportunity to track the growth of corpus luteum cysts throughout pregnancy.

Both the corpus luteum and corpus luteum cyst have distinguishing dense peripheral “ring of fire” vascularity on color Doppler imaging (Fig. 21.3a–c). These vessels exhibit low resistance and high diastolic flow on spectral Doppler. There are typically little or no internal solid components. Ectopic or heterotopic pregnancies in the adnexa imitate corpus luteum cysts because they, too, are fed by a peripheral ring of vessels and can be seen directly adjacent to a cyst (Fig. 21.4a, b). The critical distinction is made by determining if the adnexal mass is para- or intra-ovarian. Ectopic pregnancies should move independently from the ovary with pressure applied by the examiner. This “sliding sign” is not visualized during examination of intra-ovarian corpus luteum cysts, which remain coordinated in movement with the ovary. In a retrospective study of 78 pelvic sonograms performed on women exhibiting symptoms consistent with ectopic pregnancy during the first trimester, the radiologists were able to correctly identify ectopics in 23 of 27 patients exhibiting the “sliding organ sign.” Although not a strong differentiator, ectopic pregnancies also tend to be more complex and echogenic than luteal cysts when compared to the ovarian parenchyma [14].

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Fig. 21.3

Corpus luteum cyst of pregnancy. Transvaginal (a) sagittal and (b) transverse grayscale images of the ovary demonstrate an anechoic round structure with thin walls. (c) Sagittal color Doppler image demonstrates peripheral vascularity representing the “ring of fire”

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Fig. 21.4

Ectopic pregnancy. (a) Transverse view of the left adnexa depicting a thick, echogenic ring and (b) peripheral vascularity on sagittal color Doppler

Corpus luteum cysts are usually asymptomatic, especially when they are relatively small in size, as opposed to ectopic pregnancies that will invariably become symptomatic. However, large cysts can rupture, undergo torsion, and bleed [12]. Intervention is imperative for ectopic pregnancies and recommended for cysts and benign masses greater than 7 cm, but not recommended for small luteal cysts [13].

Hemorrhagic Corpus Luteum Cysts

The clinical presentation of a hemorrhagic corpus luteum cyst is characterized by more unilateral pain than its predecessors. The resolution of pain does not correlate with resolution of the hemorrhagic cyst, which can evolve over subsequent months [15]. Sonographically, the acute phase of the hemorrhage demonstrates very hyperechoic internal echoes (Fig. 21.5a, b). As the blood settles, the cyst appears more heterogeneous with thin, fibrinous septations that are without color Doppler flow. The clot retracts to the walls of the cyst, appearing as a solid or reticular hyperechoic structure. Throughout this course, the cyst should always remain well defined with enhanced through-transmission owing to the predominant presence of non-bloody cystic fluid. If the cyst is not intact and the patient is symptomatic, a diagnosis of rupture is supported by the presence of free pelvic fluid.

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Fig. 21.5

Hemorrhagic corpus luteum cyst of pregnancy. Grayscale transvaginal (a) transverse and (b) sagittal images of the ovary show heterogeneous echogenic material within an anechoic cyst representing hemorrhagic blood products in a corpus luteum cyst

Due to the lack of specificity observed in some hemorrhagic corpus luteum cysts, follow-up imaging may be appropriate. Growth requires continued surveillance. The presence of thick septations and nodular walls, especially when there is associated vascularity, is suspicious for neoplasia and surgical intervention must be considered. Alternatively, magnetic resonance imaging may be helpful for further characterization (Fig. 21.6a–c). By the second-trimester anatomy scan, true functional hemorrhagic cysts should have involuted.

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Fig. 21.6

Borderline mucinous tumor of the ovary. Transabdominal grayscale (a) sagittal and (b) transverse images of the ovary demonstrate a predominately cystic mass with thick septations. (c) Color Doppler imaging demonstrates blood flow within a septation

Decidualized Endometriomas

Sonography has both high diagnostic sensitivity and specificity for endometriomas, most commonly implanted within the ovaries. These round, hypoechoic cystic masses have a characteristic sonographic appearance with regular thick walls and possibly small echogenic foci along the inner rim. Within the endometrioma, homogenous low-level echoes can resemble a hemorrhagic corpus luteum cyst; however, the latter will involute by the second trimester and the former will not (Fig. 21.7). Just as the endometrium of the uterus decidualizes under the influence of progesterone during pregnancy, about 12 % of ovarian endometriomas also undergo decidualization [16]. Their benign appearance transforms to closely mimic borderline ovarian tumors (Fig. 21.8a, b). They can rapidly develop solid intracystic papillary excrescences and irregular walls. The projections may be quite vascular and can exhibit low resistance flow. Because ovarian endometriomas are more likely to undergo malignant transformation than extragonadal types, though uncommon in reproductive-age women with small endometriomas, the correct diagnosis is crucial and particularly complicated during pregnancy.

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Fig. 21.7

Endometrioma. Transvaginal coronal image of the right adnexa demonstrates a large, thick-walled hypoechoic mass with homogeneous internal echoes

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Fig. 21.8

Decidualized ovarian endometrioma mimicking a borderline tumor. (a) Sagittal image of the right adnexa shows a cystic mass with internal irregular solid projections. Seventeen-week IUP is visible. (b) Color Doppler imaging demonstrates low-resistance vascularity within the excrescences

Though the concerning features of decidualized endometriomas tend to revert after delivery, most women elect for surgical removal while pregnant [16], thus incurring the risks that accompany such intervention. Sonography remains the best modality to characterize ovarian masses in the hopes of distinguishing decidualized ovarian endometriomas from malignant tumors, though the task remains difficult. Most notably, endometriomas tend to become slightly smaller or remain stable in size throughout pregnancy, while cancerous masses enlarge. Sonographic appearance of the wall of an endometrioma should be similar to that of uterine endometrium. MRI does not add significant diagnostic benefit and is limited by avoidance of contrast, but may assist in further comparison of endometrial tissues or ruling out a hemorrhagic corpus luteum cyst. Analysis of vascularity has not revealed consistent chronological, morphological, or flow differences [17]. If surgical intervention is deferred, monthly sonographic follow-up is recommended [17].

Dermoid Cysts

Although “dermoid cyst” is the term used most commonly, the correct medical nomenclature for these tumors is “mature teratoma.” Sonography is a valuable modality for diagnosing benign ovarian dermoid cysts. In a prospective study of 1066 sonograms of adnexal masses, radiologists correctly identified dermoid cysts 86 % of the time and never misdiagnosed them as malignant [18]. An older study of second- and third-trimester sonography of 131 adnexal lesions greater than 4 cm in diameter correctly identified 95 % of the dermoids [2]. Advances in transvaginal ultrasound technology and changes in prenatal screening since publication of the latter study have led to improved early detection of smaller dermoids. This is important given that they are the most common complex pelvic mass identified during pregnancy and would otherwise go undiagnosed until much later in 10 % of women with dermoids [45].

The accuracy of experienced medical imaging experts is especially impressive considering the wide array of appearances that dermoid cysts exhibit (Figs. 21.921.10a, b, and 21.11a, b). Nearly universally, dermoids are well-circumscribed complex heterogeneous masses arising from the ovary. They consist of well-differentiated tissues from multiple germ cell lineages (e.g., fat, calcifications, hair, and sebum), creating distinctive hyperechoic linear markings (lines and dots) within the dermoid and highly echogenic areas that strongly shadow (“tip of the iceberg sign”). This appearance may be mistaken for nearby gas-containing bowel that only allows visualization of the surface closest to the transducer. Although less common, fat-fluid levels and balls of sebum are nearly pathognomonic for dermoid cysts.

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Fig. 21.9

Dermoid. Transvaginal grayscale transverse images of the ovary demonstrate a heterogeneous round mass with punctate and linear echogenic foci representing strands of hair

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Fig. 21.10

Dermoid cyst. (a) Sagittal and (b) transverse grayscale images of the ovary demonstrate a predominately homogenous mass with echogenic areas and posterior acoustic shadowing from calcifications

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Fig. 21.11

Mature cystic teratoma and Brenner tumor. Grayscale transvaginal (a) sagittal and (b) transverse image of the ovary demonstrates a heterogeneous mass with mixed anechoic cystic and solid echogenic components

Benign cystic teratomas will not change in size under the influence of pregnancy, but are well-known perpetrators of ovarian torsion in expectant mothers [5]. The ovary will exhibit limited venous outflow on color Doppler with free pelvic fluid from edema and vascular congestion. The main ovarian vessels may appear twisted and some flow to the ovary from uterine collaterals can be present. The patient may experience repeated episodes of clinical improvement followed by pain as the torsion temporarily resolves and resumes, respectively; thus, the torsion may not be captured on a single sonographic study. Pedunculated dermoid cysts are particularly prone to torsion and subsequent rupture, themselves, and can present with an acute abdomen [12]. In these cases, surgery should be pursued, as necrosis and peritonitis may develop. Otherwise, conservative observation for small dermoids is appropriate.

Ovarian Cancer

It is estimated that 3.6–6.8 % of all persistent adnexal masses seen on prenatal sonography are malignant [3]. It is reassuring that the overall prevalence of adnexal masses in pregnancy is low, but the few cancers that exist are definite “do-not-miss” diagnoses. First-trimester sonography presents an opportunity for early detection of a cancer that is otherwise asymptomatic and, thus, diagnosed at advanced stages. As commented above in prior sections, ultrasound has shown high accuracy for determination of malignant potential, although a benign mass may occasionally mimic a cancerous mass. If sonographic findings are indeterminant, MRI may add specificity, but may also be limited by the restricted use of gadolinium contrast in the pregnant patient.

Tumor markers associated with gynecologic cancers are physiologically elevated during pregnancy. CA-125 remains the best laboratory test for ovarian cancer in non-gravid females despite variable elevations in only half of women with stage I disease [3]. However, healthy pregnant women have high CA-125 levels that peak at an average of 55 U/mL (upper limit of normal 35 U/mL) during the first trimester [19]. CEA, AFP, and beta-hCG levels increase, as well. Thus, imaging remains the best diagnostic tool for ovarian cancer in pregnancy.

The US Department of Health and Human Services published a systemic review of 14 years of literature comparing the ability of multiple imaging modalities to differentiate benign from malignant adnexal masses. The report concluded “there is no evidence to support the superiority of any single modality” for this purpose, claiming that ultrasound, MRI, and CT are nearly equivalent while FDG-PET falls short [20]. However, interpretation of sonography by experienced imaging specialists using criteria proposed by the International Ovarian Tumor Analysis study remains superior to tumor markers and mathematical predictive models [21]. In the pregnant patient, this safe and minimally intrusive modality is a logical first step.

The ultrasound examiner must first confirm that the suspicious mass is intraovarian by probing with the transvaginal transducer and observing the absence of “sliding.” Vigilance is piqued by large, complex adnexal masses [11]. Several simplified scoring systems exist to quantify the likelihood of malignancy based on a holistic assessment of mass morphology [3]. Thick, irregular septations within the mass and mural nodules or papillary excrescences are highly concerning. Serous cystadenocarcinoma exhibits more anechoic areas than the mucinous type, but never exists as a unilocular cyst [512]. However, careful evaluation of the entire cyst wall is very important because the borderline serous or mucinous cystadenocarcinoma may be almost completely unilocular, with the exception of one or more mural nodules that usually demonstrate associated vascularity by color Doppler (Fig. 21.12a, d).

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Fig. 21.12

Serous borderline tumor. Grayscale transvaginal (a) sagittal and (b) transverse images of the ovary demonstrate a large hypoechoic cystic mass with hyperechoic papillary projections. Color Doppler images (cd) demonstrate mild vascularity within the papillary projections as well as a second lesion with moderate vascularity

Solid masses may represent metastasis, commonly from the GI tract (i.e., Krukenberg tumor), or primary solid tumors of the ovary. These have a wide range of sonographic appearances, though predominantly solid tumors with few cystic components generally represent the poorest prognoses. Solid tumors are divided into epithelial, germ cell, and sex cord/stromal types with distinct epidemiology aiding diagnosis. Epithelial ovarian tumors, including cystadenocarcinomas, are the most common ovarian cancers, largely affecting postmenopausal women. On the opposite end of the spectrum are the germ cell tumors, including teratomas, which tend to afflict younger women. Sex cord/stromal tumors (i.e., fibromas, thecomas, granulosa cell tumors) are sometimes associated with familial syndromes and appear in middle age.

Generally, when color Doppler is applied to solid components of malignant neoplasms, increased disorganized vascularity is revealed. Spectral Doppler may demonstrate low resistive and pulsatility indices, representing high blood flow to the tumor. Free fluid in the abdomen is likely indicative of maternal ascites from tumor spread. Surgical removal of suspicious masses is recommended in order to protect the patient and fetus. When performed in the second or late first trimester, complication rates are low and most babies will be delivered at term.

Abdominal Mimickers

Appendicitis can present similarly to complicated right-sided adnexal masses due to its location near the right ovary. Classically, acute epigastric pain shifts to the right lower quadrant and is associated with nausea, vomiting, and anorexia. Throughout pregnancy, the enlarging uterus forces the appendix slightly higher than McBurney’s Point (normally located one-third of the distance on an imaginary line from the right anterior superior iliac spine to the umbilicus), but this change is not significant during the first trimester. Pregnant women are also more likely to present with digestive or urinary complaints than nonpregnant women, which can mimic normal pregnancy symptoms.

CT is often utilized for diagnosis of acute appendicitis in nonpregnant women. However, in those who are pregnant and presenting with right-sided pain, sonography is an excellent alternative to avoid radiation. MRI can also be used as a problem-solving tool when ultrasound is indeterminate. The inflamed appendix appears as a large (greater than 6 mm), fusiform, blind-ending structure with thick, hyperemic walls. The appendix will be noncompressible and, in cases of rupture, surrounded by a small amount of fluid. Sometimes, a hyperechoic appendicolith is discovered occluding the appendiceal lumen.

If the appendix has ruptured, the wall will not be intact, allowing fluid (e.g., feces, pus) to collect at the opening. If it does not remain localized, the noxious fluid can irritate the uterus, resulting in higher rates of preterm labor and fetal loss. This is further exacerbated by delayed operative intervention in pregnant women. A sonographic work-up for appendicitis must exclude ectopic/heterotopic pregnancies and ovarian torsion if the patient presents in the first trimester and abruption in the third trimester. Pyelonephritis and round ligament pain remain clinical diagnoses.

Pregnancy induces changes in the urinary system, including dilation of the ureters and collecting systems. Right pelvocaliectasis and ureterectasis are more prominent due to dextrorotation of the enlarging uterus, although hormonal influences on the smooth muscle of the ureter can cause fullness bilaterally. Previously asymptomatic ectopic kidneys lying low in the pelvis can cause displaced “flank” pain from vesicoureteral reflux and ascending urinary tract infections. The pain can mimic an adnexal origin. Sonography will likely show hydronephrosis in a pelvic kidney located near an ovary, with infection confirmed by urinalysis.

Summary

A comprehensive sonographic examination of the pelvis in the first trimester can reveal a spectrum of incidental findings that share their space with a growing uterus. Though most of the pathology discussed in this chapter is also encountered in non-gravid females, the unique hormonal environment of pregnancy can instigate complications or cause otherwise benign-appearing masses to look suspicious. Sonography remains the superlative modality for examination of the adnexa and for distinguishing malignant from benign masses, thus allowing pursuit of early intervention when safest during the pregnancy or if complications such as torsion are deemed likely. Its role during pregnancy surpasses tumor markers and can help clarify the physical exam, which is confounded by shifting anatomy. Sonography is also superior for ascertaining the hazards of uterine fibroids, a potentially serious roadblock to implantation, fetal growth, and later delivery. Sonography’s vital role during early pregnancy will continue to grow with increased utilization of three-dimensional images.

Teaching Points

·               First-trimester sonography leads to earlier detection of small masses that would otherwise go undiagnosed until symptomatic or at an advanced stage. Early exams should cover a comprehensive inspection of the pelvis.

·               Regularly scheduled obstetric sonography offers the opportunity to follow up and track first-trimester incidental findings for growth or complications.

·               Though most pelvic masses identified in the first trimester are benign, malignancy is occasionally seen. Sonography in conjunction with color Doppler can help make this distinction.

·               Fibroids are the most common gynecological masses in gravid and non-gravid women, alike. Two- and three-dimensional sonography can both be useful for localizing and measuring fibroids to determine if they will present challenges during pregnancy and labor.

·               Sonography has high accuracy in the characterization of adnexal masses and determining their potential to undergo torsion. This can be very helpful during pregnancy, a time when cysts are more likely to rupture or hemorrhage and cystic or solid masses have more opportunity to be a fulcrum for ovarian torsion.

·               Sonography remains superior to tumor markers for ovarian cancer detection during pregnancy.

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