Chapter 2. Gyn - Uterus

Welcome to chapter 2. which presents how to locate and describe the uterus and its characteristics. Techniques for imaging include both transabdominal and transvaginal approaches.

The most common uterine variations and abnormalities seen by ultrasound will be described.

Objectives:

By the completion of this Section the participant will be able to:

1.Describe ultrasound characteristics and size/location of the uterus

2.Place calipers in the correct locations to measure length, width, and depth of the uterus

3.Recognize common signs of uterine fibroids and be able to locate a fibroid on an image of a uterus

4.Describe the 4 typical fibroid locations in the uterus

5.Describe phases and typical measurements of the cyclic endometrial phases and how they are interpreted

6.Recognize a uterine malformation such as bicornuate or septate uterus.

UTERUS

The uterus is the most prominent landmark in the pelvis, aside from the bladder. It is located posterior to the bladder, so locating the bladder is helpful in finding the uterus. The uterus varies in size and shape, but the NORMAL adult uterus has fairly consistent dimensions. The cervix occupies about 1/3 of the entire uterine length. ¹

Figure 1. Average dimensions of the uterus, Image 1

The average dimensions are:

Length – 8 cm

Width - 5 cm

Depth (sometimes called ‘height’) – 3 cm

*An easy way to remember this is to think of 5 (width) + 3 (depth) =8 (length)

Uterine Shape

The uterus is typically shaped like a pear or a mango. If it has a more rounded shape, that can indicate a condition known as , adenomyosis, which we will be explained later in this section.

Uterus position¹

The position of the uterus varies somewhat from person to person. Sometimes the uterus is angled forward, and sometimes it is angled back toward the rectum. There can also be some lateral deviation – sometimes the uterus is angled a bit toward either the right or left.

In looking for the uterus, be aware that it is not always exactly midline.

Figures 2.a, b, c. Uterine positions.

Figure 2.a Illustration of uterine position variations

Figure 2.b Images comparing anteverted (left image) andretroverted (right image)

Figure 2.c Images of uterine positions: top image anteverted, bottom image retroflexed

A full bladder helps to visualize the uterus when doing a transabdominal scan, but keep in mind that if the bladder is too full it can displace it either to one side, or to the back, making it more difficult to see.

Uterine measurement²

Measuring a uterus should include the fundus to the cervix. If the uterus is ‘verted’ or straight, measure its length from the outside edge of the top of the fundus in a straight line to the external cervical os, keeping the line mid uterus, and following the axis of the uterus. Ideally the uterine lining, or endometrium, should look like a stripe down the middle of the uterus, and be continuous with the cervical canal as one line. This demonstrates a true midline view of the uterus.

Figure 3. Uterine measurement sagittal view. Image 4

Uterine measurement - length

A flexed uterus is one in which the cervix curves either forward or backward from the main axis of the uterus. When measuring the length in this case, you have two options – you can measure as you would for a verted uterus, or you can make one measurement from the fundus to the internal cervical os, then make a separate measurement of just the cervix, adding the two together.

Figure 4. Uterine measurement - length. Image 5

Uterine measurement - depth

When measuring the depth of the uterus, measure from the anterior surface to the posterior surface of the uterus. Find the part of the uterus about a fourth or a third distance down from the fundus, or wherever it seems to be the largest. Place the calipers on the outside edge of the uterine border. Be sure to place the calipers and line at 90 degrees (or perpendicular) to the straight axis of the uterus, as in Figure 5.

Figure 5. Uterine measurement - depth. Image 6

Uterine measurement - width

To get a transverse view of the uterus, view the uterus in a sagittal view aligning the fundus in the center of the screen. While holding that position, slowly rotate the probe, making sure that the notch is pointing to the women’s right side. To measure the uterine width:

Place the calipers where the uterus is the widest. This often requires sliding the transducer up and down transversely along the uterus to find the widest view. This view is often located just below where the fallopian tubes emerge from the uterine cornua. Look for the uterine arteries that can sometimes be seen just below the cornua (as demonstrated in the image below). A transverse view of the endometrium should be seen if the view is correct. The uterine arteries may also be seen on one or either side, aslo seen in the image below.

In the image below (Figure 6), the uterine arteries are indicated by the red arrows.

Figure 6. Uterine measurement - width. Image 7

Uterine Measurement - Endometrium.

When measuring the uterus, the endometrium must also be measured.

The endometrium needs to be measured because it often aids in learning menstrual stage, causes of abnormal bleeding, or signs of an early pregnancy. To measure the endometrium, view the uterus in the sagittal plane, and measure at the widest area, perpendicular) yellow dotted line in Figure 7) to the sagittal axis (dotted green lines) as seen in the image below. Always measure the endometrium in the sagittal view and NOT the transverse view.

Figure 7. Uterus measurement - example. Images 8-9

There is a border between the endometrium and the myometrium, making is relatively easy to measure. As explained in the Foundations Course, an echogenic line is created at the border of two different tissue densities (with different echotextures). This allows to judge where to place the calipers for measurement. The line may not be distinct in some conditions, but seeing the difference in echotexture will usually allow one to make a reasonable measurement.

Description and measurement of the endometrium is essential for making clinical decisions to manage or treat quite a number of gyn and early pregnancy complications. More detail about the endometrium is reviewed later in this chapter.

Uterine enlargement may be due to multiparity, or it may indicate a condition to be evaluated (such as a fibroid, or adenomyosis), as will be reviewed in this chapter.

Myometrium

The myometrium of the uterus is the muscle tissue. The uterus is comprised primarily of muscle tissue, designed to expand during pregnancy, and contract to expel both cyclic menses, as well as a baby during labor.

Figure 8. Myometrium characteristics. Image 10

The myometrium looks fairly homogeneous, often with some irregular echoes. Calcifications might be seen in the arcuate arteries of elderly women, and sometimes within the uterine muscle itself. In the above image (Figure 8) there is a small benign calcification noted by the red arrow. Calcifications are very dense, and therefore have a brighter echo.

Uterine blood vessels can be seen both by transabdominal and transvaginal approaches at the periphery of the myometrium.

Mixed echogenicity – dense “spots” causing shadows (like sunrays) can be indicative of adenomyosis. If there are hypoechoic areas within the myometrium, or at its periphery, this may indicate blood vessels. A way to tell if this is the case is to apply color doppler to observe for blood flow.

Rounded areas of different echogenicity with borders can be indicative of fibroids or adenomyosis . ^3,4 We will discuss fibroid identification in this section

Mometrium Echotexture

Figure 9. Myometrial echotexture variation. Images 11-12

The images in Figure 9 demonstrate the difference in echotexture between a normal uterus with smooth homogeneous echogenicity, and a uterus with more “coarse” texture – demonstrating increased vascularity or possible endometrial implants.

Myometrium (C/S scars)

While scanning a woman who has had a previous Cesarean section, it is important to look at the anterior surface of the uterus in the lower uterine segment, to see if there is an indentation. This indication is where the C Section scar is located.⁵

Figure 10. C/Section notch examples in non-pregnant women. Images 13 -14

If there is only a small indentation, with adequate myometrium between this notch of the scar and the endometrium (as in the left image), this is not of concern.

In Figure 10, the image on the left is a uterus with a small notch indicating the C/Section scar. The scar does not dip into the endometrium.

If, however, the endometrium appears deflected upward toward the outer edge of the uterus in the scar (as in the right image of Figure 10), this typically indicates a C/section scar defect. There is very little myometrium between the endometirum and the serosal edge of the uteurs. If a pregnancy implants there, it may invade outwardly, causing a rupture. This condition will be described in the First Trimester course, discussing the potential dangers of a pregnancy located in this area (called a C/Section Scar ectopic pregnancy).

it is beneficial to find and evaluate the scar prior to a pregnancy to evaluate its depth and determine if it represents a defect in which an early gestation might implant. More about C/S scar pregnancy is reviewed in the First Trimester course.

FIBROIDS

Fibroids are a very common finding in women, with an incidence of up to 50% in some populations, and up to 80% in others. Fibroids are sometimes called myomas or leiomyomas. They are rounded densities arising from myometrial tissue and are similar to scar-like structures. Fibroids are thought to be linked to a type of collagen defect, and it has some of the same properties as keloid scarring of the skin.^2,3

Young women can have fibroids, but there seems to be a higher incidence in women older than 30. There is a higher incidence in dark-skinned women as well, just as there is a higher incidence of keloid formation in dark-skinned women.

Fibroids almost always benign - they can be asymptomatic, or they can cause pelvic pain or heavy menstrual bleeding.

A very rare condition known as leiomyosarcoma is malignant form of fibroid²The incidence is 0.64 per 10,000 women, and account for 1% of all uterine malignancies in women who have fibroids. These are more likely to be seen in older women (average age at diagnosis is 51), in obese women, and those who have taken Tamoxifen or had radiation therapy for cancer treatment. Ref. 1.Stephenson The hallmark feature that differentiates it from a benign fibroid is that it is rapidly growing. These malignant tumors do NOT arise from benign tumors, so you can reassure most women with fibroids that these are NOT malignant and usually don’t require treatment unless they are symptomatic.

Fibroids are described by both their size and their location. Location has a large impact on how symptomatic they are, and on how they may affect a pregnancy, discussed later in the First Trimester course.

Figure 11. Illustration of uterine fibroid locations

General Uterine Location: fundal, central, lower uterine segment, anterior/posterior, lateral.

More specific descriptions:

1. Subserosal (just below the outer serosal layer of the uterus)

Intramural (embedded in the muscle or myometrium)
Submucosal (impinging on the mucosal lining next to the endometrial cavity)
Pedunculated means that it is attached with a stalk. It can be either inside the uterus or outside the uterus

One of the first ways you will notice the possibility of a fibroid is by noting the contour of the uterus. It appears “lumpy” instead of smooth, as indicated in Figure 12. The image on the left shows a normal uterine contour, and the image on the right demonstrates an irregularly shaped uterine contour.

Figure 12. Uterine contour with fibroids - right image is normal, left image distorted with fibroids. Images 15-16

Myometrial Fibroids - Appearance and characteristics

The appearance is typically a circular distortion of myometrial texture. It can be dense enough to cast either an acoustic shadow, or edge shadows. Figure 13 demonstrates the typical echotexture of a fibroid.

Figure 13. Myometrial fibroid. Image 17

The image below (Figure 14) is an example of a fibroid casting a shadow. By looking intently at this image from a distance, you can begin to see the round structure. The shadow helps to identify the lower border of the fibroid. This is an example of how an artifact (shadow) can assist with structure identification when it might otherwise be difficult to see

Figure 14. Intramural fibroid casting shadow. Image 18

Linear striations

Another hallmark of fibroids are alternating light and dark shadows called “linear striations” that radiate through the muscle. They appear like sunlight coming through window blinds or shutters. The sound is displaced due to irregular surfaces encountered by the sound as it passes through the lumpy texture. Examples of these are in Figure 15 (below).

Adenomyosis has some of the previously described features (mottled appearance and linear striations), but adenomyosis is typically a more diffuse pattern of mixed echogenicity, rather than having definition or border.

Figure 15. Uterine fibroids with linear striations. Images 19-20

Borders

The other notable feature of fibroids is that they typically have borders that are easily identified, as seen in Figure 16. Adenomyosis has some of features in common with fibroids, but adenomyosis does not usually have the border definition of fibroids.

Figure 16. Fibroids demonstrating fibroid borders, Image 21

Submucosal fibroid

Below (Figure 17) are examples of fibroids loated very near or impinging into the endometrium These tend to be the most symptomatic in terms of bleeding. However, very large fibroids in other uterine locations can also cause heavy bleeding.

Figure 17. Submucosal fibroids. Images 22-23

Intramural fibroid

The image in Figure 18 shows a fibroid within the muscle. If you look at the outer contour of the uterus, there is no bulging, so the fibroid is fully contained within the uterus, This is why a fibroid may not be detected with just a bimanual or digital exam.

Figure 18. Ingramural fibroid in transverse view of uterus. Image 24

Subserosal fibroid

A subserosal fibroid in a transverse view of the uterus is shown in Figure 19, but its location on the uterus places it right at the cornual edge. It is possible that this fibroid could be blocking the entrance of the fallopian tube into the uterine cavity, potentially causing difficulty in achieving a pregnancy.

Figure 19. Subserosal fibroid. Image 25

Cervical-Lower Uterine Segment Fibroid

And here are 2 examples of fibroids located low in the uterus and even on the cervix. These are not troublesome except in the case of pregnancy where they have a potential for obstructing cervical dilation in labor.

Figure 20. Fibroid in the anterior lower uterine segment. Image 26

Endometrial (submucosal) Fibroids

The submucosal fibroid in Figure 21 is so large that it is occupying the entirety of the uterine cavity, causing it to be distorted This could be the cause of very heavy menstrual bleeding, since the fibroid does not allow for complete contraction of the muscle to clamp down on the bleeding arterioles during menstruation.

Figure 21. Endometrial fibroid occupying the entire uterine cavity. Image 27

Calcified fibroid

Sometimes fibroids will have calcifications within them (as shown in Figure 22 below), making them a bit easier to identify.

Figure 22. Calcifications in the fibroid. Image 28

Pedunculated fibroid

Below is an example of a pedunculated fibroid (Figure 23). It is lseparate from the uterus on a stalk. We know this is a fibroid because the ovary is seen in a different location when the probe is moved. This fibroid seems a bit larger than the uterus itself.

Figure 23. Pedunculated fibroid. Image 29

Adenomyosis

Adenomyosis is a condition seen commonly in women, more commonly in women who have had a number of pregnancies. It is also more common in women who have had a number of uterine surgeries. Adenomyosis differs from endometriosis in its etiology and general location of endometrial implants; adenomyosis is confined to the uiterine myometrium.

Adenomyosis is thought to occur in about 60% of women experiencing progressive dysmenorrhea, heavy menstrual bleeding, and midline dyspareunia.²

The most prevalent theory of the cause is migration of endometrial glands through tiny tracts into the uterine muscle. This occurs when there is breakage of the barrier between the endometrium and the myometrium, such as placental invasion during pregnancy, surgical disruption of the barrier (D&C). These glands tend to penetrate into the myometrium progressively, resulting in myometrial thickening. These glands then enlarge, causing interstitial bleeding, a cause of increased dysmenorrhea and heavy menstrual bleeding. They expand cyclically, just like the endometrium, in response to hormonal changes. These pockets or areas of endometrial implants also cause the uterus to expand, often resulting in asymmetrical uterine enlargement, or a generalized global shape to the uterus.²

What we know is that pieces of the endometrial lining embed into the uterine muscle by way of tiny tracts. Wherever they land, . These pockets or areas of endometrial implants cause the uterus to expand, and it causes heavy bleeding and pain in most women who have it.

Figure 24. Illustration of adenomyosis in the uterus

Adenomyosis signs

The uterus in Figure 25 (below) has a globular shape, and mixed echogenicity. There are no distinct borders seen, so a fibroid is less likely.

The other way to tell a woman has adenomyosis is by looking at the endometrial definition. There should be a sharp contrast between the brighter endometrium and the darker myometrium. If that border or definition is unclear or “fuzzy”, this means that the junctional zone (thin area of muscle between the endometrium and the myometrium) is indistinct. This, along with the other uterine features and clinical symptoms, can suggest adenomyosis.

Figure 25. Appearance of adenomyosis of uterus on ultrasound. Image 30

There is normally a distinct border that distinguishes the myometrium from endometrium. As explained in the Foundations Course, an echogenic line is created at the border of two diferent tissue densities (with different echotextures). This provides a definite line from which to make our measurements. The line may not be as distinct in some conditions (like adenomyosis), but seeing the difference in echotexture will usually allow one to make a reasonable measurement.

In adenomyosis, the junction between the endometrium and myometrium (called the junctional zone, or EMI: Endometrial-Myometrial Interface) is often blurred (as in Figure 26), representing openings or tracts through which the endometrium may migrate.

Figure 26 Blurred junctional zone indicative of adenomyosis, Image 31

ENDOMETRIUM

The next focus is on the endometrium. There are 2 basic layers – the functional layer and the basal layer. These layers change in response to the hormones in the normal menstrual cycle. The basal layer remains essentially the same, but the functional layer is what thickens and becomes engorged with tiny vessels to prepare to support an implanting embryo.

Figure 27. Anatomy of the endometrium - illustration and image 32

The reasons for closely evaluating the endometrium thickness and characteristics are:

--To determine woman’s menstrual stage

--To determine if she has adequate hormonal support when she is trying to conceive

--To detect a cause of irregular bleeding

--To rule out significant abnormality (cancer or precancer) if she has abnormal or irregular bleeding (especially if she is postmenopausal)

Endometrium

When measuring the endometrium, it should be viewed in the long or sagittal axis. As shown on an earlier slide, the endometrial depth should be measured at the widest part, and from the bright outer edge of the basalis to the outer edge of the basalis on the opposite side. the endometrium should NOT be measured in a transverse plane. This is shown in Figure 28 below.

Figure 28. Measuring the endometrium. Image 33

Endometrium - cycle phases^2,6

As the uterine lining responds to hormone increase during the regular cycle, these are the representative changes that happen in each stage:

The early proliferative phase is when a woman has just menstruated and is starting a new hormonal cycle. The lining is typically thin and you may only see the basalis layer.

The late proliferative phase occurs just prior to ovulation where the lining us just beginning to thicken, but is not yet “dense”

The secretory phase is seen after ovulation, where the lining is thicker and more hyperechoic (greater density). You can no longer see the differentiation between the basalis and functional layers. This is a normal finding in a menstruating woman during the second half of her cycle.

Figure 29. Cycle phase descriptions of the endometrium with image examples. Images 34-37

The following Figures are additional examples of how the phases appear on ultrasound.

Endometrium: Early Proliferative Phase

This image in Figure 30 is of a uterine lining at the end of menses, and the lining is very thin. This is also how a post-menopausal lining should appear.

Figure 30. Early proliferative endometrial phase view. Image 38

The image in FIgure 31 was taken just prior to ovulation, and the basalis layer is expanding outward, showing some increase in the functionalis area. The white middle line is where the 2 edges of the functionalis layer meet.

Figure 31. Peri-ovulatory phase view of the endometrium. Image 39

The image in Figure 32 was taken shortly after ovulation, when under the influence of progesterone, the functionalis layer further thickens.

Figure 32. Early secretory phase view of the endometrium. Image 40

Endometrial phases - Secretory

The image below (Figure 32) is taken during the late secretory phase. The lining is thick and dense, becoming hyperechoic. There is also an acoustic enhancement or brightening of the uterus posterior to the lining indicating fluid component in the endometrium. As described in the Foundations Course, this type of enhancement occurs when sound passes through structures containing fluid, which is true of a very mature moist endometrium.

Figure 33. Secretory phase view of the endometrium. Image 41

Endometrial phases: Menstrual

Figure 34 represents the appearance of the endometrium when menses is almost complete. The bit of irregularity to the surface of the endometrium suggests that there is a bit more debris to be shed..

Figure 34. Post-menstrual view of the endometrium. Image 42

To restate, the importance of evaluating the endometrium is to provide clues to determine whether the woman:

1. Is ovulating correctly

2. Is developing an appropriate lining for a pregnancy

3. Has an over-developed (or incompletely shed) lining that can build up over time to become endometrial hyperplasia or eventually endometrial cancer (due to hormonal imbalance).

4. Has an endometrial polyp or fibroid that can contribute to abnormal or heavy menstrual bleeding

Endometrium - Abnormal bleeding

Postmenopausal endometrium should always be evaluated if there is any vaginal bleeding in a woman who has had no more periods in at least 6 months. Abnormal thickening of the endometrium in a woman who is not producing hormones is a worrisome finding, and pre-cancer or cancer must be ruled out.⁷

Figure 35. Abnormal uterine bleeding - postmenopausal bleeding

Use of a transvaginal ultrasound is preferred but not always possible in an elderly woman who may have severe atrophic vaginal changes.

The concern about postmenopausal bleeding (or any abnormal bleeding even in younger women), is that there could be endometrial hyperplasia, which can lead to atypia and pre-malignancy.

The incidence of malignancy in a symptomatic bleeding postmenopausal woman is 1-14%. But if an ultrasound is performed before an endometrial biopsy, this can be reassuring that hyperplasia is not present. The first line of assessment is a transvaginal ultrasound because of its high-negative predictive value of a thin endometrium. In other words:

If the endometrial measurement is less than LESS THAN 4mm, her risk of malignancy is 1/917. If the measurement is GREATER than 4-5mm, in symptomatic bleeding postmenopausal woman, pathology cannot be ruled out.⁸

Endometrium - polyps

Polyps are simply thickenings of mucous tissue (polyps can be in the nasal cavity, colon and any area of the body with a mucous membrane). The symptoms typically include irregular spotting, often associated with activity or sexual intercourse, or there may be no symptoms at all. If a polyp’s size is significant, it could be a factor in a woman being unable to conceive.

The chance that a polyp is cancerous is less than 1% (about 0.3%), but that risk increases after menopause ⁹

Figure 36. Endometrial polyps - 4 examples. Images 43-46

The polyps shown in the images in Figure 36 are small, rounded densities seen best during the pre-ovulatory phase where they are not obscured by the thickened endometrium.

It may not be possible for someone performing a POCUS exam to diagnose polyps, especially when only transabdominal imaging is used. But if they are noted, it is important to refer the woman for more detailed evaluation if she is symptomatic. If these are seen as an incidental finding (one you are not actually looking for), it is acceptabole to observe and repeat the ultrasound again at a later time, unless the woman is symptomatic.

Another very clear example of a polyp is shown in the image below (FIgure 37). Polyps are brighter than the surrounding tissue since they are denser tissue than proliferative endometrium. However, in secretory (generally dense endometrium) it is more difficult to visualize.

Figure 37. Endometrial polyp noted in proliferative phase. Image 47

Figure 38 shows an example of a very tiny endometrial polyp in 2 views. Once again, if this is an incidental finding, and the woman is not having symptoms, it is acceptable to observe and repeat the ultrasound again at some interval to be certain this is not growing.

Figure 38. Two views of very small endometrial polyp. Images 48-49

ABNORMAL UTERUS - COMMON MULLERIAN DEFECTS

When beginning to scan women, you may notice that some women may have an unusual shape to the uterus. This can be due to congenital structural abnormalities called Mullerian defects. Although there are specific names for the various configurations of the uterine abnormality.

After performing a number of PCOS exams, the typical appearance of a normal uterus will be familiar, and therefore an abnormal uterus will be easier to identify.

If the uterine distortions are mild, there is usually no complication. However, some uterine cavity variations can cause difficult IUD insertion, as well as heavier menstrual bleeding (as in the case of a complete double uterus, called a didelphic).

It can also contribute to abnormal pregnancy implantation, increased miscarriage, and increased risk of preterm birth.

The next illustrations (Figure 39) shows characteristics of these variations.

Figure 39. Illustrations of congenital uterine malformations

Septate uterus

In Figure 40(below), a 2D image (on the right) appears fairly normal. However, a transverse 2D view of the uterine cavity might show a concern for 2 horns. A 3D coronal view would be the gold standard for viewing an abnormal endometrial cavity and improve accuracy in diagnosis. A clinican providing basic POCUS exam is unlikely to have 3D ultrasound capabilty, but this image demonstrates that referral for advanced imaging can make the final diagnosis when this abnormality is suspected.

Figure 40. 3-D and 2-D images of septated uterus. Images 50-51

The normal uterus is shown here to provide a comparison to the abnormalities that will next be discussed. The normal uterus appears in the long view (top), and then in 2 transverse views (mid-uterus, and cervical regions). The endometrium is uninterrupted and appears as a single echogenic area. Typically, the endometrium will appear flattened in the mid section, and then become more rounded in appearance at the level of the cervix (bottom left image, Figure 41).

Figure 41. Illustrations and images of viewing normal uterus in sagittal and transverse planes. Images 52-54

ABNORMAL UTERUS - COMMON MULLERIAN DEFECTS

One of the first things noticed when viewing the uterus is the general shape and contour, creating suspicion of a septate or bicornuate uterus. Although fibroids can also distort a uterus, look for the presence of two endometrial canals in the abnormal section, which rules out fibroid. Also be aware that an early pregnancy can create an irregular uterine contour.

Figure 42. Irregular contour of a septate or bicornuate uterus. Image 55

Arcuate uterus

The arcuate uterus is different from the normal uterus in that it has a “dipping down” of the inner fundus of the uterus. It is not a true septum, but is a “bowing downward” of the top of the uterus. When imaged in a transverse plane , the middle of the endometrium has 2 sections; however, the further down on the uterus you scan (toward the cervix), the more the central transverse endometrium becomes one section instead of two. Only the very top of the fundus separates out in the lateral view. (Figure 43)

Figure 43. Illustrations and images of viewing arcuate uterus in sagittal and transverse. Images 56-58

Septate uterus

The septate uterus is the most common uterine malformation, AND it is associated with poorest outcomes. There is an increased risk of miscarriage, and in particular, recurrent miscarriage.

After imaging the uterus in the sagittal plane. the next step would be to rotate the probe to view the uterus in the transverse view, starting at the fundus and moving downward toward the cervix.. This should include a transverse view at the fundus, at the midportion of the uterus, and again at the cervix. This would help you to identify at what point in the uterus the endometrium changes from having 2 sections, back to having a single canal.

Figure 44. Illustrations and images of viewing a septate uterus in sagittal and transverse. Images 59-61

Septate uterus risks¹⁰

The septate uterus is the most common uterine malformation, and it may be associated with poorest outcomes. There is an increased risk of miscarriage, and in particular, recurrent miscarriage.^11,12Some evidence suggests that a uterine septum may increase the risk of other adverse pregnancy outcomes such as malpresentation, intrauterine growth restriction, placental abruption, and perinatal mortality.

Surgical removal of the septum can reduce miscarriage rate from 85% to 3.7% in one study¹¹. l The criteria for recommending septoplasty varies by organization and concern for adverse impact on pregnancy outcome. Many women with a small septum conceive and birth normally.

Septate vs bicornuate uterus

The biggest difference between a septate and a bicornuate uterus is that the outer fundus of a septate uterus is rounded, where a bicornuate uterus has two distinct horns, and an indentation at the fundus (hence the term “bicornuate”). (Figure 45)

Figure 45. Illustration of uterine configuration of septate versus bicornuate uterus

Bicornuate uterus transverse view

In viewing the bicornuate uterus in the transverse plane, you will see two separate endometrial areas all the way down to (and including) the cervix. In some bicornuate or uterus didelphys, there will be a single cervix with 2 os’s. There may also be two separate cervices, as demonstrated by the diagram in Figure 46.

Figure 46. Illustrations and images of viewing a true bicornuate uterus with double cervix in sagittal and transverse views. Images 62-64

Bicornuate Uterus Risks

The overall incidence of bicornuate uterus is 0.4% of the general population. In women having infertility and a history of miscarriage, about 4.7% have a bicornuate uterus. This condition increases:

Incidence of heavy menstrual bleeding (bleeding from 2 endometria)
Risk of first and second trimester loss
Preterm delivery less than 28 weeks
Low birth weight babies
Malpresentation at delivery
Increased risk of postpartum hemorrhage¹¹

One possible treatment is removal of the mid-section, creating a single uterine cavity.

Septate Uterus - Pregnancy

The image in Figure 47 demonstrates what appears to be a pregnancy in either a septate or bicornuate uterus, demonstrating the left section with an endometrium, and the section on the right with a gestational sac. This condition would warrant consultation and more advanced imaging.

Figure 47. Image of a gestation in one side of either a septate or bicornuate uterus. Image 65

The same image below (Figure 48) shows the overall uterine outline (outlined by the red dotted line), the septum (green dotted line), and the endometrium in the non-pregnant side.

Figure 48. Image of a gestation in one side of either a septate or bicornuate uterus with markers. Image 66

ENDOMETRIUM

Viewing the endometrium can be helpful in determining the cause of postpartum or post-miscarriage persistent bleeding. It is especially beneficial when looking for retained products of conception with remaining circulation. Women with this condition often present with persistent bleeding weeks after a normal birth or miscarriage. This bleeding has typically lasted weeks beyond the expected time for it to resolve.

The presence of post spontaneous abortion (SAB) debris within the endometrial cavity is a common finding. These remnants may appear as echogenic material on ultrasound and can be associated with irregular bleeding or discomfort. Careful evaluation is necessary to distinguish benign retained products from more concerning pathology, especially in patients with persistent symptoms. In some cases, further management or intervention may be warranted to ensure complete resolution and avoid complications such as infection or scarring.

The image below (Figure 49) is of a transverse view of the endometrium. There is still debris in the cavity, but with color flow turned on (notice the red and blue flecks), there is nothing inside the uterus with blood flow to indicate tissue with active circulation. The image below indicates that the contents of the endometrium are fluid-filled (darkened area) and some inert tissue sloughing along the edge.

Figure 49. Image of endometrium post-ab in transverse view of the uterus. Image 67

Endometrial Fluid

As described earlier, there can be fluid in the endometrium. Most of the time this is a benign finding, but it might be associated with conditions like a recent ruptured ovarian cyst, or even menses.

Figure 50. Image of fluid in the endometrium. Image 68

Endometrium Abnormalities =abnormal thickness or hyperplasia

If the endometrium appears thickened and cystic, and this is cause for concern. This is often seen in women who have been experiencing prolonged heavy bleeding. It can occur as a build-up of tissue over time when there is inadequate regular monthly shedding. This can be common in women with chronic anovulation due to hormonal imbalance (such as polycystic ovarian syndrome, women who have excessive estrogen production due to obesity).

Instead of the lining shedding and returning to normal thickness, the uterus continues to bleed due to the presence of hyperplastic (abnormally grown) tissue. This does not allow for the uterine arterioles to adequately shut down.

Incomplete or infrequent shedding of the endometrium can lead to endometrial hyperplasia. Once complex endometrial hyperplasia develops, this puts the woman at increased risk for endometrial cancer.

An abnormally thickened lining is shown in Figure 51.

Figure 51. Image of endometrial hyperplasia. Image 69

Endometrium abnormalities - endometrial cancer

The image in Figure 52 is an even more alarming image of a uterine cavity, fully occupied by a very irregular-appearing mass. This mass has mixed echogenicity, and represents endometrial cancer. This was not a fibroid, and if color flow were to be applied, it is likely that there would be a good bit of vascularity within the mass. Color flow was not used in this instance since it was taken with an older portable machine without color flow capability. Vascularity would indicate the presence of living tissue (neoplasm) requiring additional blood supply. This woman requires referral for further evaluation and treatment.

Figure 52. Image of endometrial (uterine) carcinoma. Image 70

CERVIX

Although cervical ultrasound might seem more relevant to obstetric evaluation, it is important to observe even during a gyn exam. In some cases, the uterus and cervix can be measured separately, but most of the time the cervical length is incorporated into the overall uterine length. The value of looking closely at the cervix in a gyn patient is to be able to identify any abnormal densities (cervical polyps are very common). If a cervical polyp is seen at the external os, and it is causing the woman intermittent bleeding, it is a good idea to look at it first with ultrasound to determine whether its stalk originates in the cervix itself, or whether it originates from higher up in the endometrium. This could affect how polyp removal is managed.

Figure 53. Images of sonographic view of cervix in sagittal view. Images 71-73

Endocervical canal

The image in Figure 54 is of an obstetric patient, but it demonstrates identification of the endocervical canal as a hyperechoic (brighter) line of thickened or dense tissue. Sometimes the cervical canal may also appear dark due to the presence of uterine bleeding, or simply a collection of serous fluid, which would not be an abnormal finding. The cervix is measured from the internal os to the external os. This is reviewed in greater detail in the Second-Third Trimester Course.

Figure 54. Image of cervical length measurement in sagittal plane, Image 73

Cervical Nabothian cysts

It is common to see small inclusion cysts within the cervical canal just as commonly as those seen on the surface of the cervix. These are almost always benign. The only concern would be if they are exceptionally large or if color flow is seen within it. On rare occasions, a large cyst in the cervix that contains color flow or debris can be a cancer. When a large cervical cyst is noted, it is best to refer the woman for more advanced imaging.

Figure 55. Image of small cervical inclusion cysts (Nabothian cysts) in sagittal plane. Image 74

ADDENDUM: HOW TO PERFORM THE TRANSABDOMINAL PELVIC ULTRASOUND

PERFORMING THE TRANSABDOMINAL PELVIC SCAN

STEPS

1. Select the appropriate transducer: 3.5 MHz curvilinear transducer is best; use adequate ultrasound gel

2. Select the appropriate preset in the machine

3. Place the probe midline on the woman just above the symphysis pubis in the longitudinal position. Make sure that the probe notch is facing toward the woman’s head.

4. Adjust the gain to achieve an adequate brightness on the screen – the bladder is most anterior and should be dark black or hypoechoic. The myometrium should appear uniformly darker grey, and the endometrium lighter grey.

5. Maneuver the probe (right to left or up and down) to visualize the endometrium and cervical canal as continuous.

6. Enlarge the view of the uterus using Zoom or depth to so the size fills at least half of the view on the display

7. Slide the probe side to side in the sagittal position to view the right and left areas of the pelvis.

8. Return to midline and rotate the probe 90 degrees to view the pelvis in a transverse manner. Be sure that the probe notch is facing toward the woman’s right

9. While in transverse, slide the probe up and down to view the entire uterus and adnexa in the transverse

10. Identify the vaginal stripe, which will direct you to the cervix

11. Identify the cervix and angle the probe upward to see the uterus

12. Measure the uterus in the sagittal view (length, depth, and endometrial thickness

13. Rotate the probe and slide up to near the uterine fundus transversely to obtain a transverse measurement of the uterus.

14. Return to midline and slide the probe sagittaly to the woman’s right until you no longer see the uterus; this region is where you look for the right ovary. Look for the right iliac blood vessels to help you identify the outer boundaries for where the ovary should be located.

15. Measure the ovary’s length (the longest axis) and depth. Then rotate the probe (notch to the woman’s right) to obtain a transverse view of the ovary. Then measure the width of the ovary.

16. Repeat this process (step 14-15) on the woman’s left side to identify and measure the left ovary.

17. Scan the area behind the uterus and cervix (culdesac) and note if there is any fluid (seen as a dark area

18. Be sure to record each view, properly measure, and annotate so that a report can be generated at the end of the scan.

Summary - GYN II Uterus

•The uterus is the most prominent landmark in the pelvis and its average dimensions are 8cm (L) by 5 cm (W) by 3 cm (D)

•The uterus can assume different shapes but most commonly pear-shaped

•Common benign myometrial abnormalities are fibroids.

•Fibroids can be pedunculated, submucosal, intramural, and sub serosal

•Adenomyosis is a common cause of heavy menstrual bleeding and dysmenorrhea; it demonstrates sonographic characteristics that can aid in the diagnosis

•The sonographic characteristics of the endometrium change throughout the menstrual cycle

•Polyps are common endometrial findings that can be identified sonographically

•Common uterine Mullerian defects are described: bicornuate and subseptate uterus

YOU MAY NOW TAKE THE QUIZ AND MOVE TO THE NEXT CHAPTER. YOU WILL NOT BE ABLE TO OPEN THE NEXT CHAPTER UNTIL YOU COMPLETE AND PASS THE QUIZ WITH 100%. YOU WILL HAVE AS MANY TRIES AS YOU NEED TO GET ALL THE ANSWERS CORRECT!

POCUS and IUD Evaluation

Chapter 2. GYN - Uterus