One of the most important benefits of 3D ultrasound is the ability to display planes that cannot be acquired by direct transducer application to the patient (see Figures 47-1 and 47-2). Consequently, these planes are reconstructed from within the volume and include the most important aspect of the female pelvis: the coronal view.5,6 When looking at the images of the uterus tubes and ovaries diagrammed in anatomy books such as Netter's, the coronal view of the pelvis is generally the plane used to display the anatomy.7 Unfortunately, traditional 2D ultrasound technology has not been able to provide this orientation to view the female pelvis, because the port of entry of the probe (whether it be the vagina or the surface of the abdomen) does not provide a direct path to this view. Now, however, using 3D ultrasound we can reconstruct this coronal view and show the shape of the uterine cavity as well as the outline of the serosal surface of the uterus, information which neither 2D ultrasound alone or hysterosalpingography can provide. Abuhamad et al showed how easy it is to obtain the coronal image of the uterus from within a volume.8 They demonstrated the z-technique, which is a simple method by which practitioners can be taught to manipulate the volume so as to obtain the coronal view of the uterus in less than 30 seconds.
The ability to detect uterine shape abnormalities that may impact fertility is one of the most important contributions of the coronal display of the uterus (Figures 47-8,47-9,47-10,47-11,47-12,47-13,47-14,47-15,47-16,47-17,47-18,47-19, and 47-20). It is well known that uterine anomalies can be associated with a significantly higher proportion of infertility and first- and second-trimester pregnancy loss compared with women who have a normal uterus.18 Therefore, the correct diagnosis of uterine abnormalities in those women is paramount to rendering the proper treatment. Until recently, an MR was needed to map out uterine shape abnormalities. Currently, 3D reconstruction of the Z plane is a quick, easy, and accurate method of displaying these clinically important uterine shape defects.5,6,8,19,20 Wu et al undertook a prospective study of 40 patients with histories of infertility or habitual miscarriages and showed that 3D ultrasound had a sensitivity and specificity of 100% each for detecting all congenital uterine abnormalities.19 Raga et al also studied 30 normal patients and 12 with müllerian abnormalities, and showed that 3D ultrasound was accurate in detecting the anomaly in all cases.20 Although these investigations did not have large numbers, the data are extremely promising.
A and B: Two images of a septate uterus showing that the septum extends almost all the way down to the cervix, forming 2 completely separate horns at the uterine fundus but only 1 cervix. Note that in (B) one of the cornua is particularly well seen, showing the interstitial portion of the tube (arrow).
A: Transverse view of a uterus showing 2 islands of endometrium with myometrium between them. This is a uterine abnormality, but it is difficult to determine the specific diagnosis in 2D. B: Coronal view of the same uterus showing a completely septate uterus with a broad septum at the fundus thinning out towards the lower uterine segment.
Subseptate uterus showing a broad septum extending only halfway down the uterus. Note the widely separated uterine horns but lack of indentation of the serosal surface.
Bicornuate uterus. A: Transverse view through the fundus of the uterus showing 2 separate islands of myometrium, similar to what is seen with a septate uterus (see Figure 47-9). B: Reconstructed coronal view of the same uterus showing that this is actually a bicornuate uterus due to the indentation of the serosal surface of the uterus of at least 1 cm (arrow).
Subseptate uterus containing a twin pregnancy in one horn. This pregnancy is at very high risk for adverse outcome particularly in the first trimester.
A: Transverse view through the fundus of the uterus showing 2 different islands of endometrium. This appearance cannot be used to differentiate accurately the septate, arcuate, or bicornuate uterus. B: Coronal view of the same uterus, showing that it is arcuate with only a mild dip at the uterine cavity at the fundus.
A: Transverse view through the fundus of the uterus showing 2 islands of endometrium, one larger than the other. This appearance suggests a uterine shape abnormality which is asymmetric. B: Coronal view of the same uterus, showing a septate uterus with one rudimentary horn, resulting in marked asymmetry. This uterus would probably function as a unicornuate uterus.
Surface rendering of the serosal surface of a uterus, which is bicornuate but asymmetric with one horn being much smaller than the other. This view does not demonstrate the cavity, making it impossible to determine whether or not the rudimentary horn (arrows) communicates with the body of the uterus.
Unicornuate uterus. A: Longitudinal view of a normal-appearing uterus in a patient that was not suspected of having a uterine shape abnormality. B: Reconstructed coronal view of the same uterus showing that the uterine cavity does not have a normal triangular shape but rather a unicornuate appearance.
Coronal view of a complex uterine abnormality showing a single horn of the uterus with a tiny rudimentary attempt at a second horn (arrow) that did not develop.
A: Complete separation of the uterine cavity and cervix into two, with a bicornuate component owing to the indentation of the serosa at the fundus of the uterus. B: A close-up of the double cervix in the same uterus.
Uterine didelphys. A: A 2D view of completely double uterine bodies, widely separated. B: The coronal view of the same uterus shows the wide separation between the 2 uterine fundi in this uterine didelphys. This type of uterine abnormality is particularly difficult to image, both in 2D and 3D, due to the wide separation between the 2 horns.
Coronal view of the uterus containing 2 polyps. This coronal view demonstrates calipers measuring the 2 polyps.
The specific diagnosis of a septate versus a bicornuate uterus has been particularly confusing when viewing standard 2D ultrasound images, because the internal uterine anatomy looks similar, but the external (fundal) uterine shape distinguishes the 2 entities. The incidence of the septate uterus is considerably higher than the bicornuate uterus,18 and has important prognostic and treatment ramifications. Traditionally, any uterus where 2 endometrial islands were separated by myometrium in 2D transverse section was often erroneously called a bicornuate uterus. This is due to the sonographer having to try to recall the relative shape of the uterine fundal shape by memory while scanning, rather than being able to see the entire uterus on image. Now, 3D ultrasound can differentiate between these 2 very different entities accurately and easily using the coronal view of the endometrial cavity.18,19, and 20 It is crucial to make the correct diagnosis of a septate uterus, since this type of uterine abnormality has a much higher incidence of infertility and spontaneous first-trimester miscarriage when compared with the bicornuate uterus.18 The correct diagnosis can lead to important treatment options as the septate uterus can be treated surgically with good success, whereas the bicornuate uterus often does not require surgery. The arcuate uterus, while not as severely abnormal as the complete septate or subseptate uterus, is still associated with a significantly higher incidence of second trimester losses and preterm labor compared to women with normal uteri.18 Other types of uterine shape abnormalities are complex, and may include a combination of bicornuate and septate uteri as well as duplications of the cervix, rudimentary horns which may or may not connect with the main uterine cavity and which may be a potential site for ectopic gestations. This important uterine anatomy can easily be mapped out with a 3D coronal reconstruction of the image of the uterus, thus providing a correct diagnosis without having to go to other cross-sectional imaging techniques such as MR.18,19, and 20
Uterine Polyps and Fibroids
The coronal view is also very valuable for detecting the presence of endometrial polyps and fibroids within the uterine cavity (Figures 47-21,47-22,47-23,47-24,47-25,47-26,47-27,47-28, and 47-29).2,4,5,21 Endometrial polyps are typically seen as rounded masses with a sharp demarcation or interface between the polyp and the rest of the endometrium. Frequently, these polyps are identified more accurately with the coronal view than with the traditional 2D imaging of the uterus, owing to a better display of the uterine cavity showing both cornua and cervix in the same plane.4,5 This type of display allows for a better grasp of the position of the polyp within the cavity and its landmarks. Doppler can also demonstrate blood flow to the polyp in these 3D reconstructed views and may be of additional benefit in diagnosing polyps.
Coronal view of a uterus containing multiple polyps. A small amount of fluid was in the uterus permitting a surface rendering of these polyps.
A: Reconstructed coronal view of a uterus containing a single polyp with color Doppler, demonstrating the blood flow to the polyp. B: Volume of a different uterine polyp using color Doppler and rendering of the entire volume using a transparent technique. Note the blood flow to the polyps, and a small amount of fluid in the intrauterine cavity from the sonohysterography.
Submucosal fibroid. A: Longitudinal view with standard 2D imaging showing a small polyp at the fundus of the uterus. The relationship to the uterine cavity is difficult to assess using this view. B: Reconstructed coronal view of the same uterus showing the relationship between the small fibroid and the uterine cavity. The fibroid appears to be partly submucosal but with a good distance from the outer edge of the polyp to the serosal surface. This type of information is crucial to the surgeon treating this patient.
Large submucosal fibroid. A: Transverse view using standard 2D imaging showing a submucosal fibroid surrounded in part by endometrium. B: Coronal view of the fibroid as it projects into the uterine cavity using the endometrium as a contrast agent. This image is reconstructed at the site of connection between the fibroid and the myometrium, demonstrating the stalk (arrows) of this submucosal fibroid.
Coronal view of a submucosal fibroid involving the cornua. This fibroid is only partly submucosal but also extends very close to the serosal surface of the uterus.
3D TV-CDS of cervical fibroid before (top) and after UAE (bottom) multiple vessels remained after U.A.E., possibly from ovarian artery collaterals.
3D TA-CDS prior to U.A.E. showing marked peripheral and central vascularity.
Reconstructed coronal view of the uterine cavity with an IUD in a perfect location.
A: IUD in the lower uterine segment, considered somewhat low in position using standard 2D imaging. B: Coronal view of the same uterus showing that the IUD is actually embedded with both arms in the myometrium in the body of the uterus.
The location of fibroids within the uterus is a very important use for 3D ultrasound in general and the coronal view in particular.1,4,5 The coronal view of the uterus is instrumental in displaying the correct location of fibroids with respect to the endometrium, including detecting the proportion of submucosal component accurately and the distance between the outside of the fibroid and the serosal surface. These important measurements and determinations can best be examined by navigating through the volume and demonstrating tangentially the correct plane to best display these relationships. Volume sonography has also been helpful in monitoring fibroids before and after invasive or noninvasive procedures designed to shrink fibroids. Fleischer et al have shown that 3D Doppler sonography can assess fibroid vascularity before and after uterine embolization, providing a method of monitoring such patients.22,23 Three-dimensional color Doppler sonography is accurate in depicting fibroid vascularity and can occasionally reveal collateral flow not detected with arteriography.23
Detection of ovarian collaterals to the uterus by 3D color Doppler is also helpful prior to attempts at uterine artery embolizations, because embolization may occasionally put patients' ovarian function at risk. Three-dimensional color Doppler sonography performed after uterine artery embolization may also indicate the completeness of the embolization.22,23 This study reported patients who have become more symptomatic after the embolization and have persistent blood flow. Similarly, the finding of a single vessel within the pedicle of a fibroid may be a contraindication for embolization. It is possible that coexistent adenomyosis may be better seen with 3D color Doppler sonography.22
The Uterus and IUD Location
The coronal view of the uterus is also extremely useful for evaluating the presence of foreign bodies within the uterus (Figures 47-29,47-30,47-31,47-32,47-33,47-34,47-35,47-36, and 47-37).24,25 The position of intrauterine devices (IUDs) in particular has been especially difficult to evaluate accurately with traditional 2D ultrasound, because the IUD is a 3D device as is the endometrial cavity. Three-dimensional coronal displays have made IUD localization very simple.25 It is remarkable how many IUDs are actually embedded within the myometrium—a fact that has remained unrecognized with traditional 2D ultrasound. Whether an embedded IUD is symptomatic, and actually causes the pelvic pain that brings patients to ultrasound, remains an unanswered question. In our experience, many IUDs which appeared to be positioned correctly or slightly low using 2D ultrasound alone were actually imbedded, at least in part, within the myometrium.
A: Low-lying IUD in the lower uterine segment seen with 2D ultrasound. B: Coronal view of the same uterus showing that the IUD is twisted with one arm embedded just above the cervix.
3D TA-CDS showing focal hypovascular area within fibroid.
A: Longitudinal view of the uterus showing a normal-appearing location of the IUD within the uterine cavity using 2D ultrasound. B: Coronal view of the uterine cavity of the same uterus showing that the left arm of the IUD is actually embedded in the myometrium in a patient who had left lower quadrant pain.
A: IUD located in the cervix on 2D ultrasound. B: Coronal view of the same uterus showing that the IUD is embedded in the cervix with the right arm of the IUD in the cervical substance.
A: An IUD seen in a normal position within the uterus using 2D ultrasound. B: Multiplanar reconstruction and rendering of the IUD shows that it is bent and not filling the uterine cavity. C: Close-up reconstructed view of the left arm of the IUD shows that it is partly embedded within the myometrium.
Coronal view of an IUD in the lower uterine segment/ cervix showing that both arms of the IUD are embedded in the lower uterine segment.
Shadow of the IUD. A: Multiplanar reconstruction and rendering of an IUD showing that the render box is just posterior to the location of the IUD, only catching its shadow. The IUD casts a shadow that is obvious on the A and B slices, which are the standard orientations usually seen in 2D ultrasound. The reconstructed images and the bottom 2 portions of the display show a shadow, which could be mistaken for the IUD itself because the source of the shadow is not appreciated on the image. B: Close-up view of the shadow of the IUD on a reconstructed coronal view of the uterus is confusing because the IUD is not in the same plane and is not shown on this image.
Multiplanar reconstruction of multiple cysts in the adnexa seen on the scan planes X and Y. The reconstructed Z plane demonstrates that the cysts connect, consistent with a hydrosalpinx.
There are important artifacts to consider when looking for an IUD using reconstructed planes.26 The most important artifact involves the shadow of the IUD, which can easily be mistaken for the actual IUD itself. In a standard 2D view, the source of the shadow artifact is obvious because the IUD itself is in the same picture and is easily implicated as the cause of the shadow. A reconstructed plane from a 3D volume that contains a shadow may be confusing because the shadow is isolated from its origin and the IUD is in a different plane not displayed. There is often a shadow in a single reconstructed image where the source of the shadow is not recognizable unless the entire volume is available for review. Because it is easy to misinterpret the IUD for its shadow and miss the correct localization of the device, it is crucial to obtain the entire volume so as to navigate through the volume and follow the shadow to the IUD.