Chapter 33: SONOGRAPHIC EVALUATION OF UTERINE DISORDERS

The ability of sonography, in particular transvaginal sonography (TVS), to depict subtle changes in the myometrium and endometrium makes it the diagnostic modality of choice for the evaluation of many uterine disorders. With sonography, the uterus can be imaged in several scan planes. Because the images are obtained in real time, the sonographer can empirically alter the scanning plane and gain settings for optimal depiction of the endometrium and myometrium. Because of its proximity to the uterus, a transvaginal transducer/probe can enhance the sonographic depiction of the uterus and endometrium.

Once a uterine lesion is suspected clinically, transvaginal sonography can be used to establish the presence, size, extent, and internal consistency of the lesion and to detect associated pathology, such as liver metastases. Sonography has a major role in differentiating palpable uterine masses from those that arise from adnexal structures. The specific diagnosis can be confirmed by endometrial biopsy, through dilation and curettage (D&C); by other imaging techniques, such as hysterosalpingography; and, in some cases, even by direct hysteroscopic visualization. Magnetic resonance imaging (MRI) and computed tomography (CT) can also demonstrate uterine and parauterine anatomy, and are particularly useful in staging known uterine neoplasms.

Transvaginal sonography has an important role in establishing the presence of adenomyosis, a common cause of pelvic pain. Although the TVS findings may be subtle at times, the solicitation of pain when the uterus is scanned is another useful hint to the probability of adenomyosis.

Transrectal sonography (TRS) and transabdominal sonography (TAS) may be useful in certain operative uterine procedures such as difficult D&Cs and placement of a tandem within the uterine lumen for localized radiation therapy.

Three-dimensional (3D) sonography has been shown to be useful in the evaluation of uterine anomalies. Three-dimensional ultrasound (US) affords depiction of the uterine fundus in the coronal plane, which is vital in distinguishing a bicornuate uterus from a septate uterus. Please refer to Chapter 47 for a more extensive discussion.

This chapter discusses and illustrates the sonographic features of the most common uterine malformations and disorders. Sonographic evaluation of the endometrium is discussed in detail in Chapter 34. For the sonographer and sonologist to distinguish normal from pathologic findings, a short discussion of the sonographic features of the normal uterus follows comments concerning scanning technique.

Both TVS and TAS have a role in the evaluation of the uterus. Whereas TVS affords detailed images of the uterus, larger uteri or those with masses larger than 5 cm may be better depicted by TAS.

For TAS, sonographic evaluation of the uterus should be performed when the patient has a fully distended bladder. A fully distended bladder displaces gas-filled bowel loops from the pelvis and places the uterus in a more horizontal plane. This orientation of the uterus relative to the transducer is advantageous because the uterus can be imaged by using the superior characteristics of axial as opposed to lateral resolution. Occasionally, the urinary bladder can be overly distended, placing the uterus out of the focal range of a focused transducer. In such cases, partial voiding will place the uterus in a more optimal focal range. In some patients with very large uterine masses, full distention of the bladder may be impossible, and adequate sonographic visualization of the uterus must be attempted without having the bladder fully distended.

When examining a pelvic mass thought to be of uterine origin, it is important to establish the continuity of that mass with the uterus.¹ Establishing that a mass is uterine involves showing that the vagina leads into the mass and that a linear echogenic interface in the uterus—the endometrium—is present. Transvaginal sonography can be used to optimize depiction of these features.

For TVS, the urinary bladder should not be overly distended. The uterus should be imaged in its long axis first, sweeping from right to left by angulating the probe. Short-axis images are then obtained. The relative position of the uterus can be inferred by the orientation of the probe that best images the uterus. For example, if the uterus is best imaged with a posterior inclination, the uterus is probably retroflexed.

The endometrium can be demonstrated in most patients as an echogenic interface or a group of interfaces in the center of the uterus. The sloughed pieces of the endometrium during menstruation usually produce a thin, broken echogenic interface. The endometrium thickens and becomes echogenic as it develops in the secretory phase. The thickness of the endometrium can usually be estimated by the distance from the proximal to distal interfaces between the hypoechoic halo that surrounds the endometrium (corresponding to the compact and relatively hypovascular inner layer of myometrium) and the more echogenic endometrium. The "natural contrast" provided by the endometrium can be used to definitively localize the uterus in relation to other masses that may surround or distort it.²

Three-dimensional US is useful in evaluation of the uterus for distinguishing bicornuate from septated uteri. Three-dimensional US can be obtained using a freehand technique or a transducer capable of an automated sweep. Please refer to Chapter 47 for more details.

Sonography can accurately depict the position, size, shape, and texture of the uterus. Each of these features should be carefully assessed and documented sonographically (Figures 33-1, 33-2, 33-3 and 33-4).

The position of the normal uterus is immediately posterior to the floor and dome of the urinary bladder. The fundus is usually anteriorly flexed when compared with the cervix (anteflexed). A retroflexed uterus can be a normal variant. Retroflexed uteri appear more lobular in contour than anteflexed uteri, in part because there tends to be altered venous drainage with consequent myometrial suffusion. Transvaginal scanning can improve depiction in most of these cases. Because of the posterior position and curved surface of the fundus, however, it may be difficult to obtain detailed images of the fundal portion of a retroflexed uterus. Furthermore, the endometrial layer may not be seen with TAS. In some severely retroflexed uteri, an interface perpendicular to the endometrial lumen can be seen; this probably results from an indentation and compression of the myometrium and uterine serosa.

On transverse sonograms, a significant range of variation in the right-to-left or anterior–posterior position of the uterus can be observed in normal individuals. These positional variants are in part dependent on the degree of bladder and rectal distention present when the patient is examined.

The flexion and position of the uterus are not as readily depicted by TVS as by TAS. In general, if the uterus is best depicted on TVS when there is a posterior orientation of the probe, the uterus is most likely retroflexed. Conversely, if the uterus is best depicted when the probe is placed in the posterior vaginal fornix and aimed anteriorly, the uterus is most likely anteflexed.

Before discussing the size and shape of the uterus, the various anatomic segments of the uterus are noted here. There are 3 main divisions of the uterus: the fundus, the corpus or body, and the cervix. The segment of the uterus that lies superior to the entrance of the uterine tubes is designated the fundus. Inferior to the fundus and superior to the internal cervix is the corpus. The lower portion of the corpus is sometimes termed the isthmus. Although the isthmus has been designated as a separate segment of the uterus, this designation is debatable because it is not distinct—on the basis of function or anatomy—from the corpus. There is a transition from the smooth muscle wall of the fundus and corpus to the cervix, which consists of mostly fibrous tissue.

The size and shape of the uterus differ according to the patient's pubertal status, age, and parity.³ Before puberty occurs, the uterus measures 1.0 to 3.3 cm in length and 0.5 to 1.0 cm in width. The cervix and isthmus comprise a greater proportion of the uterus (up to two-thirds of the total length), and are thicker than the fundus. In contrast, the nulligravidous, normal postpubertal uterus measures 7 cm in length, 4 cm in width, 4 cm in height, and has a relatively thicker fundus and shortened cervix. The multiparous woman typically has a uterus that measures an average of 1.2 cm greater in all directions, compared with the nulligravida.⁴ A postmenopausal woman has a uterus that is smaller than the normal postpubertal woman. The average dimension of the postmenopausal uterus ranges from 3.5 to 6.5 cm in length and is 1.2 to 1.8 cm thick.⁵

The texture of the normal myometrium is consistent throughout all age groups and is of a homogeneous low to medium echogenicity. Small vessels (between 1 and 2 mm in diameter) can sometimes be seen between the middle (spiral) and outer layers of myometrium. It is also not unusual to have calcification of these arcuate arteries in the outer layers of myometrium in older women. The inner layer of myometrium is thin and hypoechoic. It corresponds to the "junctional zone" seen on MRI. The spiral, or middle, layer of myometrium is the thickest layer and its muscle bundles are arranged concentrically. Variations in the arrangement of myometrial muscle bundle may produce focal areas of irregular echogenicity. This may also be seen in focal areas of myometrial contraction. These should be distinguished from fibroids.

Sonography, in particular TVS, can depict a variety of appearances of the endometrium that correspond to the major developmental stages (menstrual, proliferative, or secretory). The innermost layers of the endometrium appear as a central linear echogenicity that is most prominent during menses. Surrounding this echogenic interface is a hypoechoic band that probably corresponds to the compact and relatively hypovascular inner layer of the myometrium. The endometrium thickens from 5 to 7 mm (in the proliferative phase) to 7 to 12 mm (in the secretory phase) in total anterior–posterior width.⁶ The hypoechoic texture of the endometrium most frequently seen in the proliferative phase is related to the particular arrangement of the enlarging glands and stroma. Stromal edema present in the secretory phase most likely also contributes to the echogenic texture of the endometrium during this portion of the cycle by increasing the number of interfaces between glandular and stromal elements. A small amount of intraluminal fluid can be observed during the periovulatory and secretory phase of the cycle.⁷ In addition, the innermost layer of endometrium may be edematous, giving rise to a multilayered pattern (as seen in long axis) or a "halo" configuration (as depicted on transverse scans).⁸ The endometrium appears thickened and echogenic during the secretory phase. The echogenic texture of the secretory endometrium is probably related to the hypertrophied and tortuous glands, which contain a mucinous secretion. The mucus contained within the endocervical canal is observed to become more hypoechoic near the time of ovulation, which is probably related to the high fluid content.

The endometrium in postmenopausal women should be relatively thin (<6 to 8 mm) because it is typically atrophic. There may be focal areas of calcification in the outer myometrium, representing calcified arcuate arteries and/or veins. These may be particularly extensive in diabetic patients. Echogenic foci within the myometrium may also represent focal areas of fibrosis secondary to curettage or retained foci of decidua.

On pelvic examination, a malformed uterus may be confused with an adnexal mass (Figure 33-5). Similarly, the sonographic appearance of malformations is sometimes mistaken for uterine fibroids. The most common congenital uterine malformations arise from anomalies of fusion. A T-shaped uterus is associated with a history of diethylstilbestrol (DES) ingestion by the mother of the patient. Hematometra can be secondary to congenital malformation, but it also can be acquired secondary to cervical stenosis. Each of these entities is discussed as it relates to sonographic findings.

Three-dimensional sonography has become the diagnostic modality of choice for the evaluation of uterine malformations. This is true because of its ability to depict the contour of the fundus in the coronal plane. Using this, one can readily distinguish a bicornuate uterus from a septated uterus because a bicornuate uterus has a fundal indentation whereas a septated uterus does not.

Fusion Anomalies—Bicornuate versus Septated Uterus

Early in embryonic development of the female fetus, the wolffian and müllerian duct systems interact to form the internal genitalia. The wolffian system regresses, and the uterus, oviduct, ovary, and vagina are formed from paired müllerian structures that eventually fuse in the midline.

The most common anomalies of the internal genitalia result from defects in fusion of the paired structures that form the uterus, cervix, and vagina. The degree of failure can range from partial to complete. If there is total failure of fusion, a uterus didelphys will result. In patients with uterus didelphys, 2 vaginas, 2 cervices, and 2 uteri are present. Partial fusion of the müllerian duct derivatives range from uterus bicornis unicollis (2 uterine horns, 2 cervices) or 2 uterine horns, 1 cervix) to uterus arcuatus (mildest fusion anomaly, with saddle-shaped lumen). In all of these fusion anomalies, a common central wall between the 2 uteri is present. Incomplete resorption of the sagittal septum within the uterus results in a uterus septus or subseptus, depending on the size of the septum.

Uterine malformations can be suspected from findings on pelvic examination and are diagnosed definitively by hysterosalpingography. The lesions become important to the sonologist because they can be encountered on pelvic sonography as an incidental finding and confused with an adnexal mass.

Arrested development of the müllerian ducts results in uterine aplasia; if this occurs unilaterally, a uterus unicornis unicollis is formed. The suffix cornis refers to the uterine horns; collis refers to the cervix.

Although it is usually not possible to distinguish with any confidence between the more subtle types of uterine anomalies (septated vs bicornuate uterus) on the basis of sonography, it is important to remember that other congenital defects may be associated with these uterine malformations. Specifically, renal anomalies, such as renal agenesis, may be encountered on the same side as the uterine malformation.⁹ Thus, if a uterine anomaly is suspected, one should scan the region of the kidneys.

Duplication of the uterus can be associated with an obstructed horn, resulting in hematometra. A bicornuate uterus can mimic the sonographic appearance of a parauterine solid mass; however, the typical pear shape of the uterus can be recognized on multiple sagittal scans. Sonographic recognition of a uterine septum in a gravid patient is important because of predisposition to premature labor, fetal malpresentation, and third trimester bleeding.

One of the most common uterine anomalies detected on sonography is the gravid bicornuate uterus (Figure 33-6). Commonly, the patient with this condition presents with unexplained uterine bleeding secondary to sloughing of the decidua in the nongravid horn. Sometimes the anomaly is first discovered when a nodular mass is palpated. The empty horn of the uterus can be mistaken for a parauterine mass on pelvic examination.

The nongravid bicornuate uterus usually appears sonographically as a binodular structure that is best delineated on transverse scans. It can appear quite similar to leiomyomata, except that the myometrium has a homogeneous texture as opposed to the whorled appearance of a leiomyoma. During menstruation, 2 uterine lumina may be identifiable.

Hydrometrocolpos and Hematometrocolpos

These conditions can be associated with either congenital or acquired malformation of the uterus or vagina.^{10, 11 and 12} They result from accumulation of secretions or blood within the uterus or vagina, which occur because of congenital or acquired obstruction of a uterine horn, cervix, or vaginal tract.

Obstruction of menstrual flow can be congenital and symptomatic, as in delayed menarche with imperforate hymen or vaginal atresia, or it can be asymptomatic, as in a blind horn. Previously healthy women may have neoplastic obstruction of the uterine outflow tract. In either of these cases, retrograde menstruation can occur.¹²

Premenarchal girls may accumulate clear secretions in the vagina. Patients with this condition may be asymptomatic but can present with vague pelvic discomfort or pain during defecation or urination due to compression of the rectum or bladder by the pelvic mass. Similar to delayed menarche in the otherwise healthy girl, hematometrocolpos can be encountered in patients with an imperforate hymen or vaginal atresia.

Sonographically, the distended uterus or vagina appears as a pear-shaped structure with either anechoic or echogenic internal contents. If clotted blood is contained within the uterus, echoes emanating from the clotted blood can be seen. These are usually mobile when the patient is scanned in various positions.

A small amount of fluid or blood can be present within the endometrial cavity during menstruation or in pelvic inflammatory disease. Intraluminal fluid may be associated with endometritis from pelvic inflammatory disease. In postmenopausal women, intraluminal fluid can be associated with endometrial carcinoma.¹³

If there is an imperforate hymen, transperineal scanning can be used to assess the vagina and uterus.

T-Shaped Uterus

A specific uterine anomaly has been encountered in women whose mothers received DES as part of a therapeutic regimen. Diethylstilbestrol was widely prescribed to pregnant women between 1940 and 1960 as an anti-abortifacient. A great many women who were exposed to DES in utero have multiple benign abnormalities of the genital tract.¹⁰ In addition, more than 300 cases of clear-cell adenocarcinoma of the vagina have been reported to date.

Sonography can be useful in detecting the so-called T-shaped uterus associated with DES exposure. The volume of the T-shaped uterus, calculated from length, width, and anterior–posterior dimension, has been reported to be significantly less than a control group of women at similar ages.¹⁰ The T-shaped uterus derived its name from the hysterographic appearance of the uterine lumen. The abnormal shape and decreased size of the uterus can be detected sonographically by a greater-than-usual transverse dimension and by decreased thickness of the fundus.¹⁰

Sonohysterography may be helpful in defining the endometrial lumen in malformed uteri. Sonographic delineation of the endometrium, particularly in the luteal phase, can also be helpful in the assessment of a malformed uterus. Particular attention should be directed toward assessment of the uterine fundus because bicornuate uteri have a definite cleft as opposed to septated uteri, which do not.

INFLAMMATORY DISORDERS

Pyometrium or suppurative endometritis may occur as a sequela to postpartum infection or after an attempted abortion with septic complications (Figure 33-7). Pyometrium may also result from cervical stenosis secondary to radiation treatment of the uterine cervix for cervical carcinoma.¹² Endometritis is occasionally seen with salpingitis. Endometritis can also cause thickening of the endometrial interfaces, particularly as depicted by TVS.

The sonographic appearance of the postpartum uterus is discussed in Chapter 30. Normally, the linear intraluminal interface is centrally located and the endometrial layers are closely opposed.

Puerperal infection is usually due to retrograde contamination of the uterine cavity by normal or pathogenic vaginal flora introduced during labor. Prolonged labor, premature rupture of membranes, retention of placental tissue, and cervical and vaginal lacerations are known risk factors. Clinically, this condition is suspected when a yellowish-green to black discharge is found in the lochia. The endometritis can progress to a myometritis, parametritis (pelvic lymphangitis), pelvic abscess, and septic pelvic thrombophlebitis.

It is clinically helpful to have a sonographic evaluation of the extent of the disease or involvement of the adnexa. The sonographic appearance of pelvic and adnexal inflammatory disease is discussed in Chapter 36. Endometrial inflammatory suppuration can be depicted as irregular hypoechoic areas in an enlarged uterus.

Clinical Aspects

Uterine leiomyomata are benign tumors that consist of smooth muscle and connective tissue. They are the most common tumors encountered in gynecologic practice and are commonly referred to as fibroids (Figure 33-8). It is estimated that leiomyomata are present in 20% of women older then 35 years. Such tumors are estrogen dependent and usually regress after menopause. Leiomyomata are most prevalent in black women and other dark-skinned groups. The usual clinical picture is a palpable mass in a middle-aged woman, but leiomyomata may be associated with excessive menstrual bleeding and pelvic pain. They may cause infertility due to distortion of the isthmic portion of the tube. In addition, fibroids can contribute to uterine dystocia and disruption of endometrial interfaces, or to pelvic obstruction in the laboring patient.

The fibroid is important to the sonologist for 2 reasons. First, as a neoplasm, fibroids do have a small malignant potential. More commonly, however, the clinician needs to differentiate a palpable mass of uterine origin from an adnexal mass. For these reasons, detailed sonographic examination of fibroid tumors is warranted.

Leiomyomata usually develop in the myometrium of the upper contractile fundal and corporeal portions of the uterus. Only 3% of the leiomyomata are of cervical origin. Microscopically, these tumors arise from the smooth muscle and connective tissue that surround the smaller vessels coursing within the outer layers of the myometrium. Intramural leiomyomata cause the uterus to contract, and the resultant compression of these tumors is believed to displace them either toward the peritoneal surface to form subserous nodules or toward the endometrial cavity to produce submucous nodules. Intraligamentary nodules can arise by extrusion of the intramural nodule retroperitoneally into the areolar tissue between the leaves of the broad ligament. Also, rarely, leiomyomata can develop from fibromuscular structures in the round ligament or from those surrounding the vessels.

Leiomyomata of the uterus are usually multiple and of various sizes. A solitary nodule is found in only 2% of patients; the number of tumors in a uterus may reach hundreds. The size ranges from microscopic to massive, with 100 pounds being the largest single fibroid reported.¹⁴ Microscopically, each nodule is delineated by a pseudocapsule through which vascular channels enter and arborize within the tumor. As the tumor increases in size, it may eventually outgrow the blood supply, and central ischemia is followed by various stages of degeneration.

Degenerative processes may be benign or malignant, asymptomatic or symptomatic. Asymptomatic, benign degenerative processes include atrophic, hyaline, cystic, myxomatous, lipomatous, and carneous degeneration.

The symptomatic group includes carneous degeneration, infarction, and infection. Under the effect of strong uterine contractions, rotation of nodules within the pseudocapsule may shear supplying vessels and result in necrobiosis of the tumor. This process is most frequently seen during pregnancy.

Both subserous and submucous nodules may become pedunculated and undergo torsion of the pedicle, with subsequent infarction, degeneration, necrosis, and potential infection. For some pedunculated nodules whose circulation is occluded, attachment to the omentum or intestine allows the entry of new vessels and a revitalized blood supply. Under such circumstances, the pedicle may atrophy and the nodule may become completely detached from the uterus, giving rise to a so-called parasitic fibroid.

Submucous fibroids are prone to necrosis because their blood supply is frequently insufficient to support the tumor mass. More importantly, their exposed position subjacent to the uterine lumen predisposes them to ascending infection. Pelvic inflammatory diseases may involve adjacent fibroids by direct extension or through the lymphatics; curettage can injure submucous nodules and introduce bacteria. Occasionally, when the fibroid is infected, the central core may be filled with purulent material.

Malignant change in the tumor is a generative, not a degenerative, process. Although the occurrence of leiomyosarcoma in preexisting leiomyomata is 0.2% or less, the prevalence of leiomyomata results in this form of sarcoma being the most common malignant stromal uterine tumor (25%). Malignancy in a fibroid is seldom diagnosed preoperatively because there are no characteristic symptoms to distinguish this entity from preexisting fibroid nodules. Sudden accelerated growth in a previously static tumor and postmenopausal enlargement should suggest the possibility of a superimposed malignant process.

The clinical manifestations of fibroids are variable and depend on the size and number of the tumors, age of the patient, proximity of the tumor to the endometrial cavity, mobility of the fibroid (sessile or pedunculated), and presence or absence of degenerative processes. Submucous tumors typically encroach on the endometrium and distort the endometrial cavity. Because of pressure necrosis, alteration in the vascular architecture of the endometrium may occur and cause excessive menstrual bleeding to be the presenting symptom. When submucous fibroids outgrow their blood supply, surface necrosis, slough, and bloody discharge may result. Pain is not a common symptom except in the presence of degenerative changes or torsion of the pedicle of a subserous nodule. Pelvic discomfort due to pressure on the surrounding organs may be present with large tumors, but often the only symptoms are abdominal enlargement and a palpable mass. Pedunculated submucous leiomyomas ("fibroid polyps") can be partly or completely extruded through the cervical canal and can cause infection, necrosis, and ascending endometritis. This event may also be associated with invasion of the uterus. Larger fibroids, particularly of the intraligamentous type, may compress the ureter with resultant hydroureter and hydronephrosis.

Sonographic Features

The typical sonographic appearance of leiomyomata consists of mildly to moderately echogenic intrauterine mass(es) that cause nodular distortion of the uterine outline. Small intramural or submucous leiomyomata may be recognized by their distortion of the normally linear central endometrial interfaces. The solid nature of a fibroid often may cause an indentation on the bladder or rectum.

The echogenicity of a fibroid depends on the relative ratio of fibrous tissue to smooth muscle. With a more fibrous component, there is increased echogenicity of the nodule. The sonographic texture of fibroids also depends on the type and presence of degeneration and on the vascular supply. Interfaces between the normal myometrium and the pseudocapsule of the mass can sometimes be demonstrated. With TVS, the distortion of the endometrial lumen associated with the fibroid can be demonstrated. In some fibroids, the whorled internal architecture can be appreciated. The whorled appearance corresponds to bundles of smooth muscle and connective tissue that are arranged in a concentric pattern. In some cases, leiomyomas are only minimally echogenic and appear as cystic masses, except that their posterior wall is not as prominent as expected. Irregular anechoic areas may be seen within leiomyomata if cystic degeneration has occurred. Calcific degeneration within a leiomyoma is quite common and can be recognized as clusters of high-level echoes that are associated with distal acoustical shadowing.

The most common cause of calcification within the uterus is calcific degeneration within a fibroid. Twenty-five percent of one series of 75 cases of fibroids had calcifications.¹⁴ The pattern of calcification differed from a few small foci to a large rim of globular calcification. If the calcification is extensive and located along the anterior portion of the fibroid, it may prohibit complete sonographic delineation of the mass. Intrauterine calcifications can also be encountered in uterine sarcomas, but this condition is much less common than in leiomyomata.

Other types of degeneration within leiomyomas that produce sonographically recognizable changes in uterine texture include cystic, myxomatous, and hyaline degeneration. Among these, hyaline degeneration is the most common and appears as anechoic areas within a fibroid. Areas of hyaline degeneration can be distinguished from areas of cystic degeneration in that areas of cystic degeneration will usually demonstrate distal wall enhancement. Accelerated enlargement of a fibroid after menopause may indicate sarcomatous degeneration. There do not appear to be any sonographic signs that distinguish benign from malignant changes, however.

Leiomyomata that are pedunculated can be confused with other adnexal masses if their pedicle is not visualized. The most common location of pedunculated leiomyomas is superior to the uterine fundus. In most cases, an echogenic interface corresponding to the tissue plane connecting the fibroid and the fundus can be delineated. Pedunculated subserosal fibroids can also extend into the broad ligament, and thus appear as an extrauterine mass. The typical whorled configuration of the fibroid usually can be recognized, however. To ascertain whether or not a mass is connected to the uterus by a pedicle, applying slight pressure to the mass while performing TVS has been suggested. The mass will move with the uterus if the two are connected. This procedure should be performed by an experienced sonographer or sonologist and dynamically observed with real-time sonography.

Submucous leiomyomata may be difficult to differentiate from intramural leiomyomata. Both may produce distortion of the endometrial interfaces. Submucosal fibroids are best documented by TVS or by sonohysterography. Submucosal leiomyomas tend to be more echogenic than endometrial polyps.

Fibroids can be particularly difficult to detect with TAS in the retroflexed uterus. Because the uterine fundus curves posteriorly in the retroflexed uterus, this area may be relatively hypoechoic. Appropriate gain settings and time-gain compensation curves should be used; a hypoechoic area within the fundus of a retroflexed uterus could be technical in origin rather than a fibroid.

Serial sonographic evaluation of leiomyomata can be of significant clinical value. Follow-up scans of the fibroid uterus of a pregnant woman can help assess the growth and accelerated degeneration of this mass. A study of fibroids during pregnancy revealed that the size of most fibroids remains stable during pregnancy.¹⁵ Because fibroids should regress after menopause, serial sonograms can objectively document enlargement or regression of leiomyomata in the older woman. Due to its ability to portray larger areas of interest, TAS is needed in fibroids that enlarge the uterus to over 8 to 10 weeks in size. When the uterus is smaller than this, TVS is recommended. Depiction of the endometrial interfaces by TVS is particularly helpful in identifying myometrial masses by their displacement of this interface.

Color Doppler sonography may be used to assess flow within the fibroid and its response to medical treatment. In general, well-vascularized fibroids tend to be more responsive to medical treatment than hypovascular ones. Fibroids that parasitize major vessels for their blood supply may have a low-impedance, high-diastolic flow similar to that seen in some malignant pelvic masses.

Sonographic Mimics of Fibroids

Occasionally, solid masses that are adjacent to the uterus appear as masses within the uterine contour (Figure 33-9). This finding has been referred to as "the indefinite uterus sign."¹⁶ In such a setting, a retrouterine mass may be misdiagnosed as an enlarged uterus. The most common solid masses to simulate the sonographic appearance of a fibroid are the solid ovarian tumors. In particular, cystadenofibromas can calcify, simulating the appearance of a fibroid. Metastases that settle and enlarge in the cul-de-sac, such as those associated with breast tumors, can also produce apparent enlargement of the uterine contour.

Transvaginal sonography can be helpful in distinguishing fibroids from other adnexal or ovarian masses. In particular, TVS is helpful in identifying the ovaries in patients with fibroids because it usually is difficult to distinguish a fibroid from the ovary by palpation. We have also been able to distinguish a mass, representing a tubal carcinoma, from a fibroid by using TVS.

Adenomyosis of the uterus is a condition in which clusters of endometrial tissue implant deep within the myometrium. During menstruation, significant pain can be caused by bleeding of the endometrial tissue within the muscle of the uterus. The uterus may be slightly enlarged but may be tender when gentle pressure is applied at TVS. Occasionally, this condition can be diagnosed sonographically because of a thickened and "Swiss cheese" appearance of the myometrium caused by areas of hemorrhage and clot within the muscle. In addition, the endometrial implants that burrow into the myometrium may contribute to increased echogenicity of the myometrium.¹⁷ Because the portion of the endometrium that invades the myometrium is usually derived from the basalis layer, it usually does not result in cyclical hemorrhage. Rather, a diffuse increased echogenicity of the inner- and mid-myometrial layers can be seen.¹⁸ Adenomyosis may be distinguished from intramural fibroids by color Doppler sonography. Typically, fibroids have a rim of vascularity, whereas the blood flow within adenomyosis is scattered.¹⁹ In addition, the margins of adenomyosis tend to be indistinct when compared with fibroids.²⁰

Adenomyosis is frequently associated with endometriosis. It is a frequent cause of intermittent pelvic pain and excessive bleeding typically seen in multigravid patients. On TVS, adenomyosis appears as an irregular area of echogenic myometrium sometimes with punctuate hypoechoic areas.²¹ The punctuate cystic areas usually measure between 2 and 4 mm and represent glands. These usually are in the inner myometrium. Another sonographic finding in adenomyosis is streaky shadowing due to the hypertrophied myometrium surrounding adenomyotic foci. A similar finding can be observed in patients who take tamoxifen due to reactivation of adenomyosis foci. Adenomyosis may coexist with leiomyomas. Magnetic resonance imaging may be helpful in distinguishing leiomyomas from adenomyosis because adenomyosis typically causes diffuse thickening (over 11 mm) of the junctional zone.²⁰ In addition, the focal areas of hemorrhage may be seen in T2-weighted MRI.

Transvaginal sonography also affords a means to evaluate several types of cervical masses and disorders. For this application, the transvaginal transducer/probe is usually placed a few centimeters into the vagina so that the cervix itself can be delineated.

Cervical inclusion cysts (nabothian) can be clearly identified by TVS as cystic structures within the cervix. These are created when the epithelium grows over the ostia of the glands and obstructs the egress of secretions. They are of no clinical significance.

The presence of cervical carcinoma may be difficult to delineate in its early stages by TVS. When more advanced, it usually appears as a hypoechoic, irregular enlargement of the cervix.

Because most cervical carcinomas can be identified by visual inspection and histologic studies, sonography does not have a major role in their detection or staging. Cervical carcinoma may be present in enlarged cervices, but enlarged patulous cervices may be normal. Detection of invasion into surrounding tissues is most important in assessing patients with cervical carcinoma. For this application, CT and MRI have better capabilities than sonography in detecting parametrial extension. In addition, these modalities have a higher accuracy in detecting lymphadenopathy associated with cervical carcinoma.

In the pregnant patient, sonographic delineation of the cervix by transvaginal or transperineal sonography may have important implications in the detection of clinically suspected or unsuspected cervical incompetence. This topic is addressed at length in Chapter 28.

Carcinoma of both the cervix and the endometrium may be associated with intraluminal fluid. In cervical carcinoma, this is usually related to cervical stenosis, which can occur after radiation therapy.

Carcinoma of the oviduct is a rare gynecologic neoplasm. It is mentioned in this chapter because its sonographic appearance can mimic intraligamentary or pedunculated uterine fibroids. Most patients with this malignancy remain undiagnosed both sonographically and clinically until time of surgery. Sonographically, one patient presented with a poorly defined, complex, fusiform mass concomitant with a large intramural leiomyoma. In another, a reniform, complex mass with central echogenic core surrounded by sonolucent halo was encountered. At surgery the mass depicted by pelvic sonography corresponded to a loop of jejunum infiltrated by surrounding tumor. Figure 33-9A shows a TVS of a patient with a known mass that filled the lumen of the left tube on hysterosalpingography. On TVS, an unsuspected pedunculated fibroid was found rising from the uterine fundus, as was a fusiform solid left-adnexal mass that corresponded to the fallopian tube carcinoma.

These are discussed in detail in Chapter 34; however, some information is presented in this chapter to emphasize evaluation of the endometrium when examining the uterus.

Sonography has an increasingly important role in the evaluation of certain disorders of endometrium (Figures 33-9, 33-10 and 33-11).²² Although not a primary means for diagnosis of endometrial hyperplasia, a sonographic examination performed to evaluate a pelvic mass, for example, can detect this disorder. It can also be helpful when D&C is anticipated to be difficult, as in cervical stenosis.

The endometrium in a postmenopausal woman should be thin (no more than 6 to 8 mm in anterior–posterior dimension) and regular. This size may be altered by certain medications, such as estrogen replacement therapy. This may also depend on whether this hormone replacement therapy is composed of estrogen and progesterone or unopposed estrogens, because unopposed estrogens may tend to produce more endometrial thickening than combined therapy.

When the endometrium is thicker than 8 mm in a postmenopausal woman, one should consider performing D&C or endometrial biopsy, particularly if there is postmenopausal bleeding. Occasionally, blood or mucus retained within the lumen can give the false impression of endometrial thickening. Endometrial hyperplasia should be suspected when the endometrial interface is thicker than 8 mm. Endometrial polyps can also distend the lumen with irregular punctuate echogenic tissue. Echogenic foci can be observed in the inner myometrium in women who have undergone D&C. These probably represent foci of fibrosis (see Figure 33-7E and F).

Myometrial invasion by endometrial carcinoma usually produces a disruption in a subendometrial halo, with thickening and irregularity of the central endometrial interfaces. The actual tumor may be hypoechoic or echogenic, depending on its grade.²³ In general, the more highly differentiated tumors that produce mucin and have glandular elements tend to be echogenic, as opposed to the lower grade tumors that do not form glandular elements. In addition, the echogenicity of the tumor is probably related to the number of interfaces created by the infiltrating tumor. Exophytic tumors associated with myometrial thinning may be most difficult to distinguish from truly invasive tumors. It is also conceivable that adenomyosis might simulate myometrial invasion. In some cases, intraluminal scanning may be indicated.²⁴ This procedure requires anesthesia and is usually performed immediately before intracavitary tandem placement. A less complicated alternative is the installation of saline into the uterine lumen (sonohysterography). This topic is discussed in greater detail in Chapters 34 and 38. We encourage the use of polyps forceps for removal of polyps during the initial D&C to decrease the likelihood of misdiagnosing an exophytic tumor for a deeply invasive one.

In some institutions, preoperative determination of the amount of myometrial invasion has a role in determining whether or not intracavitary radiation should be used. With deeply invasive tumors (over 50% of myometrial width), some oncologists use preoperative intracavitary radiation to decrease the likelihood of lymphatic spread. Transvaginal sonography has been shown to be an accurate means to determine the amount of myometrial invasion,²³ and it seems to be equally accurate as unenhanced MRI, but less accurate than MRI if contrast enhancement is used.²⁵

Patients who have undergone hysterectomy have altered anatomic relations in the pelvis and may be difficult to adequately evaluate by manual pelvic examination.²⁶ Detection of a pelvic mass in these patients may require additional clinical and diagnostic imaging evaluation. Removal of the uterus also makes TVS more difficult because the ovaries are more mobile.

Pelvic masses not related to the uterus can be encountered in the patient who has undergone hysterectomy or salpingo-oophorectomy. For instance, a small ovarian remnant may enlarge and produce a pelvic mass even though most of the ovary has been removed. The potential for resumption of ovulatory function remains, however, and the patient may resume production of ovarian sex steroids. The enlarged ovarian remnant is often adherent to the pelvic side wall and may also produce partial obstruction of the ureter due to compression.^27,28

Hematomas and nondistended loops of bowel may appear as masses within the pelvis of a posthysterectomy patient, depending on the organization of the hematoma. They appear as anechoic to hypoechoic masses. In the postmenopausal patient, the ovary should be small and difficult to delineate.

A portion of omentum may be rounded and appear as a soft tissue mass. This may be adherent to the vaginal cuff or cul-de-sac and mimic the appearance of an ovary. It is indeed difficult to distinguish these 2 entities by sonography. Postoperative peritoneal adhesions may enclose fluid, causing a peritoneal retention cyst.

Transvaginal sonography can be helpful in the evaluation of masses adjacent to the vaginal cuff or of adnexa in patients who have undergone hysterectomy. Due to the relatively close proximity of the transvaginal probe to the ovary, these structures can be identified and masses arising from them detected. Sometimes, however, the ability to use TVS is limited in patients who have atrophic or short vaginas due to hysterectomy.

The use of the water enema technique with simultaneous monitoring by real-time scanning is advocated for further evaluation of the posthysterectomy patient when initial sonography suggests the presence of a pelvic mass. Water distention of the rectum affords a detailed evaluation of the posterior compartment of the pelvis in a posthysterectomy patient. Only small remnants of supravaginal tissue should be present between the urinary bladder and rectum of these patients.²⁶

Radiation therapy, given to a patient with cancer, can cause areas of fibrosis, making pelvic examination more difficult. With radiation therapy, the vaginal vault becomes foreshortened, stenotic, and rigid. It is difficult to examine the adnexa or the suprapubic area. Therefore, sonography and CT can be an important diagnostic adjunct in the follow-up of such patients. Ideally, the initial examination should serve as a baseline for comparison with future studies.

Occasionally, a patient is encountered who has had a supracervical hysterectomy. This operation consists of removal of the uterus, leaving the cervix in place, creating the potential for clinical confusion of the cervix with a pelvic mass and for development of cervical carcinoma. This type of hysterectomy is not commonly performed anymore. Because edematous changes in the cuff persist for about 6 weeks, a delay in performing a baseline sonogram for 2 to 3 months after surgery is suggested. The size of the vagina and "cuff" will differ from patient to patient, depending on the age, amount of atrophic changes, type of surgery, and amount of irradiation received, if any. In general, the older the patient, the more extensive the surgery, or the greater the amount of irradiation, the smaller the residual vagina. Cuff size is also dependent on surgical technique. The degree of tissue incorporated and the type of suture used in closure will affect the cuff size. Usually, the cuff appears as a 1- to 1.5-cm structure along the upper pole of the vagina. Once the size and configuration of the vaginal cuff are established on baseline examination, the cuff should not enlarge on later studies. As the patient ages, the cuff size usually decreases. If an increase is noted on follow-up examination, the possibility of tumor recurrence should be considered. Adherent bowel or an ovary adjacent to the upper vagina can mimic recurrent tumor around the cuff. Whenever the appearances are unusual, a water enema might be helpful in identifying structures relating to small and large bowel.¹

Seromas and inclusion cysts may form in the incision site. Inclusion cysts form from fluid collecting between free leaves of the peritoneum or around adhesions. They are typically irregularly shaped and do not conform to any particular anatomic compartment.

Sonography is useful in determining the exact location of an intrauterine contraceptive device (IUCD) relative to the endometrial lumen (Figure 33-12). In most cases, the actual shaft of the intrauterine device (IUD) can be localized as an echogenic interface in its relation to the endometrium. Both metallic and nonmetallic IUDs demonstrate a shadow that is helpful in locating them. Transabdominal sonography and TVS can be used to precisely locate the position of an IUD relative to the endometrial lumen and surrounding myometrium. Three-dimensional US is particularly useful in localizing the position of an IUCD due to its ability to depict the uterine in the coronal plane. Partial myometrial implantation can be diagnosed when a portion of the IUD extends out from the endometrial surface into the surrounding myometrium. Hysterosalpingography can be used to confirm the sonographic impression of partial myometrial implantation.

A relatively new technique has been developed for embolization of fibroids. This technique involves selective injection of embolization material into the uterine arteries. The emboli obstruct arterial flow to the fibroid and reduce its vascularity significantly. This has been advocated in women with anemias or bleeding associated with fibroids that cannot be surgically removed, or those with pressure symptoms from the fibroid on the bladder.

In general, 3D-color Doppler sonography (CDS) was most useful in determining the relative vascularity and location of fibroids.²⁷ CDS is helpful in determining if a fibroid is pedunculated, because they do not respond well to embolization or are prone to slough postembolization.

MRI is the preferred diagnostic modality to determine the exact size and vascularity of fibroids prior to uterine fibroid embolization, a new technique that combines high-intensity focused ultrasound (HIFU) with precise focusing of the heated area and temperature monitoring. MRI has become an alternative method of treatment (Figure 33-13).

MRI is very helpful in the pre- and post-uterine artery embolization (UAE) assessment of fibroids.²⁸ It can determine pre-UAE the relative perfusion to the fibroid. It has been reported that immediate reduction in fibroid flow correlates to clinical response, whereas those initially high in signal intensity on T2-weighted images indicate a higher probability for volume reduction.²⁸ MRI is also very accurate in detecting coexistent adenomyosis.²⁹ The presence of adenomyosis shown on MRI should not be taken as a contraindication to UAE because most patients, in one series, showed clinical improvement after UAE.²⁹

Transrectal (TRS) and/or transperineal (TPS) sonography can provide real-time guidance for a variety of intraoperative procedures such as D&C and circlage placement (Figure 33-14) or tandem placement. With the probe within the rectum, TRS can provide the location of the external cervical os so that a dilator can be passed into the uterine lumen through the endocervical canal without fear of perforation.

The biplane transrectal sonographic probe is preferred because it images in the long axis with the linearly arranged transducer, and in short axis with the curvilinear transducer mounted on the tip of the probe. This arrangement affords confirmation of an area of interest in both long and short axes.

The probe is covered with a condom, and gel is instilled within and over the cover. The procedure should be documented on videotape with selected still frames.

Distention of the bladder is helpful to "straighten out" the uterus, thereby allowing easier insertion of D&C instruments.

Transrectal sonography allows delineation of the endocervical canal and the echogenic line representing the endocervical canal running between the external and internal cervical os. This is best seen in long axis. Axial images are useful in confirming the central position of the dilator or circlage.

Transperineal scanning may be useful in certain cases such as guided biopsy of masses within or near the vagina. Both TRS and TPS can allow the surgeon vaginal access without being in the way of the numerous probes and dilators placed within the vagina by the surgeon. This topic is more completely discussed in Chapter 39.

Transabdominal and transvaginal sonography has many applications in the evaluation of the uterus. Whereas TAS is helpful in the evaluation of large masses involving the uterus, TVS is particularly accurate in the evaluation of endometrial and cervical disorders. Three-dimensional US has important applications in the evaluation of uterine malformation. More extensive experience is needed with color Doppler sonography of uterine and endometrial disorders to determine its role. Initial reports indicate that changes in blood flow with various treatments can be monitored with this method. This may be useful in the treatment of uterine arteriovenous malformations, for example. Sonography may have a role in monitoring the treatment of fibroids with high-intensity focused ultrasound (HIFU).