Application of 3D Ultrasonography in Detection of Uterine Abnormalities

MDAs are relatively common disorders associated with adverse reproductive outcomes. Critical analyses of studies suggest that the prevalence of uterine malformation in woman with repeated pregnancy loss is about 3% (3). Uterine malformation may result from arrested development of the Müllerian ducts, failure of fusion of the Müllerian duct or failure of resorption of the median septum (4, 5).

Several classification systems describe MDAs. The most accepted system is the American Fertility Society (AFS) classification system (Fig 1).

According to AFS, class I consists of hypoplasia and agenesis. Class II represents unicornuate uterus. Categories III and IV are composed of uterus didelphys and bicornuate uteri. Categories V, VI and VII refer to septate uterus, arcuate uterus and diethylstilbestrol exposure, respectively (6, 7).

Various imaging modalities have been used to evaluate MDAs. Despite being invasive, hysteroscopy and laparoscopy are the conventional methods for assessing uterine morphology.

HSG is one of the first conventional diagnostic tools to provide valuable information about the uterine cavity and tubal patency; however, the diagnostic accuracy of hysterosalpingography (HSG) alone is only 55% in the differentiation of septate from bicornuate uteri (8). In addition, this procedure is associated with the following complications: radiation and iodinated contrast material exposures, as well as pelvic inflammatory disease (PID) and pain.

Technologic advances in imaging modalities have revolutionized the evaluation of MDAs by noninvasive tools such as 2DUS, 3DUS and magnetic resonance imaging (MRI).

Even though two dimensional sonography is routinely used because of its flexibility and moderate cost, it has some limitations. The sensitivity of 2DUS, particularly for the demonstration of fundal contour is relatively low compared with other methods (9). One of the most useful scan planes obtained on 3DUS is the coronal view of the uterus, which is usually not obtainable on 2DUS (10). Therefore, this view is a valuable problemsolving tool that assists in differentiating between various MDAs, including bicornuate, septate, unicornuate and didelphys uteri. Data acquisition time is short and images can be stored for later evaluation and analyzed as many times as necessary (9) (Figes2A-I).

Despite the high accuracy of MRI in appraising the cervix and vagina, some limitations may favor the use of 3DUS. MRI is highly operator and technique dependent, and costly. The most important advantages of real time 3DUS over MRI are lower cost, shorter examination time and wider availability (11). 3DUS has recently become the only mandatory step in classifying MDAs since there is a high degree of concordance between 3DUS and MRI in the diagnosis of uterine malformations.

3DUS images are easier to interpret in the luteal phase of the cycle due to increased thickness and echogenicity of the endometrium (9).

Although fluid instillation into the endometrial cavity enhanced endometrial visualization during transvaginal ultrasound, intrauterine lesions (e.g., polyps, fibroids and synechiae) can be diagnosed sonographically in the initial investigation without the need for fluid instillation. Using 3DUS facilitates access to the most relevant plane, and ability to visualize both the endometrium and the myometrium facilitates correct diagnosis of uterine abnormalities.

3DUS affords a more comprehensive understanding of exact the numbers, sizes and locations of intrauterine lesions. Fibroids causing uterine distortion are the most common uterine abnormalities associated with subinfertility, implantation failure and miscarriage. One of the most useful views obtained on 3DUS are views that enable a clear estimation of the relationship between the endometrium and intramural fibroids, and consider whether they distort the uterine anatomy or not.

Intrauterine adhesions have a variable appearance, ranging from small echogenic areas of focal endometrial thickening to an obliterated endometrium as in Asherman’s syndrome.

Endometrial polyps appear as persistent hyperechogenic areas with variable cystic spaces and distortion of endometrial contours. They are best visualized during the mid-cycle and not readily seen during the mid-luteal scan cycle when the endometrial layer is thick (12) (Fig 3A-D).