Fig. 7.1
Bladder nodule in the dome of the bladder wall visualized with TVS in the sagittal plane. UVS utero-vaginal septum, AVF anterior vaginal fornix
7.2.2 Assessment of the Uterus and Ovaries
7.2.2.1 Uterus
Following the assessment for anterior compartment DIE, the woman is asked to empty her bladder so the remainder of the specialized TVS may be performed without patient discomfort. The uterus is assessed for size and position (anteversion and/or retroflexion/retroversion) and myometrial/endometrial pathology. An anteverted, retroflexed uterus is not uncommonly associated with the presence of adhesions in the POD and associated bowel DIE (Fig. 7.2).
Fig. 7.2
Anteverted retroflexed uterus visualized with TVS in the sagittal plane. Note the bowel adhesion (*) to the posterior uterus
7.2.2.2 Ovaries
Endometrioma
The ovaries are assessed for size, presence of cysts and mobility. An endometrioma is most commonly described as an avascular, unilocular cyst with homogeneous low-level echogenicity (ground glass echogenicity) of the cyst fluid (Fig. 7.3); however, endometriomas may also display atypical features. In a study by Van Holsbeke et al., 3511 women with adnexal masses were scanned by experienced sonographers, and 713 (20 %) of these women were found to have endometriomas. Almost 50 % of the endometriomas in this study had ultrasound characteristics other than the typical ‘unilocular cyst with ground glass echogenicity of the cyst fluid’ [16].
Fig. 7.3
Bilateral unilocular ovarian endometriomas. Both endometriomas appear avascular with colour Doppler assessment
Less typical features included multiple locules (~85 % with <5 locules), hyperechoic wall foci, cystic-solid lesion (~15 %) or purely solid lesion (1 %) or anechoic cysts (rare, 2 %). The optimal rule to detect endometriomas has been described as ‘an adnexal mass in a premenopausal patient with ground glass echogenicity of the cyst fluid, one to four locules and no papillations with detectable blood flow’ [16]. However, the most accurate identification of endometriomas remains the subjective impression by an experienced sonologist, which provides a positive predictive value of 86 %. This is likely due to the fact that the sonologist performing the scan may be aware of the patient’s clinical history (i.e. pelvic pain).
In addition to the above-mentioned ultrasound features of endometrioma, colour Doppler findings may also be useful. Endometriomas are typically poorly vascularized, and the presence of vascularity within a solid papillary projection within the cyst may be classified as a non-endometrioma [17] and is suggestive of malignancy. It is important to be aware that decidualization of an endometrioma in pregnancy can mimic ovarian malignancy [18]. The ability to rule out malignancy in the absence of demonstrable colour flow can be limited by the experience of the sonologist and the quality of the ultrasound machine’s power Doppler function [19].
Ovarian Mobility
Ovarian endometriomas are more likely to have adhesions to the surrounding structures than normal ovaries; therefore, it is important to assess for ovarian mobility in the presence of endometrioma. Adhesions most commonly occur between the endometrioma and corresponding pelvic sidewall and/or posterior uterine surface. Endometriomas may also be adherent to the bowel and/or opposite ovary (i.e. ‘kissing’ ovaries).
In order to determine whether the ovaries are mobile, the examiner places gentle pressure against the ovary with the TV probe to determine whether the ovary glides freely against the corresponding pelvic sidewall and uterine surface. When assessing ovarian mobility along the pelvic sidewall, colour Doppler may be used to confirm the anatomical location of the pelvic sidewall by visualizing the internal iliac vessels and the relationship to the corresponding ovary. By placing pressure over the ovary, the ovary should glide freely along the internal iliac vessel. If there is difficulty in mobilizing the ovary, the examiner may use one hand to place gentle downward pressure over the iliac fossa region of the lower anterior abdominal wall, allowing further assessment of the underlying ovary for mobility. If the ovary does not glide freely against the pelvic sidewall, the nature of the adhesion is further assessed for additional involvement with the bowel and/or opposite ovary. Video 7.1 displays a mobile left ovary, which is mobilized along the left pelvic sidewall and uterus (transverse plane). Video 7.2 displays an ovary fixed posteriorly to the uterus (sagittal plane).
7.2.3 Assessment for POD Obliteration
Next, the POD is assessed for obliteration/utero-rectal adhesions using the uterine ‘sliding sign’. The most common cause of POD obliteration is the presence of adhesions between the rectosigmoid bowel and posterior uterus and/or the anterior rectum and posterior cervix. For the anteverted uterus, the examiner first places one hand over the lower anterior abdominal wall and places gentle downward pressure onto the anterior uterine fundus to determine whether a smooth gliding motion occurs between the rectosigmoid bowel and posterior uterine fundus. Next, the examiner places gentle pressure between the TV probe and posterior cervix (with the TV probe in the posterior vaginal fornix) to determine whether there is a smooth gliding motion between the anterior rectum and posterior cervix/posterior vaginal wall. If the rectosigmoid and anterior rectum glide freely against the surface of the posterior uterine fundus and posterior cervix/vaginal wall, respectively, the ‘sliding sign’ is deemed positive and the POD is recorded as not obliterated. Video 7.3 demonstrates a positive ‘sliding sign’ at the posterior uterine fundus, and Video 7.4 demonstrates a positive ‘sliding sign’ at the posterior uterine cervix. If the ‘sliding sign’ is negative in either or both locations (i.e. rectosigmoid and/or anterior rectum does not glide smoothly between the posterior fundus and posterior cervix, respectively), the ‘sliding sign’ is recorded as negative and the POD is deemed obliterated. Video 7.5 demonstrates a negative ‘sliding sign’ at the posterior uterine fundus, and Video 7.6 demonstrates a negative ‘sliding sign’ at the posterior uterine cervix.
The ‘sliding sign’ technique is modified slightly for the retroverted uterus. The examiner places the TV probe into the posterior vaginal fornix, uses the tip of the probe to place gentle pressure against the posterior upper uterine fundus and assesses whether the anterior rectum glides freely against the posterior upper uterine fundus (Video 7.7). Next, the examiner places the left hand over the woman’s lower anterior abdominal wall in order to ballot the uterus between the palpating hand and transvaginal probe (being held in the right hand) to determine whether the rectosigmoid glides freely over the anterior lower uterine segment (Video 7.8). As long as the ‘sliding sign’ is found to be positive in both of these anatomical regions, the POD is recorded as non-obliterated [20].
7.2.4 Posterior and Lateral Compartments
The ability to accurately predict pelvic compartment DIE relies heavily on the experience of the sonologist and the location of the DIE lesion. DIE lesions within the posterior and lateral compartment are typically hypoechoic and avascular in appearance. DIE lesions should be measured in the sagittal and transverse planes and assessed for infiltration and/or adhesion to neighbouring structures. DIE nodules are noncompressible and avascular, so it is also important for the examiner to place gentle pressure upon the hypoechoic mass with the TV probe to confirm it is indeed solid in nature.
The structures of the posterior compartment which are affected by DIE lesions include POD/rectrocervix, anterior rectum/rectosigmoid bowel, pararectal space, posterior vaginal wall/fornix and RVS. TVS can be used to identify DIE lesions in the anterior rectum/rectosigmoid with a high degree of accuracy. DIE nodules within the vagina and RVS are more difficult to visualize, and E-TVS techniques such as gel SVG may be used to create a stand-off effect to improve the visualization of these lesions.
Lateral pelvic DIE lesions occur in the USL, parametria and the pelvic sidewall; pelvic sidewall and ureteric lesions are challenging to visualize due to the lack of anatomical landmarks and greater distance from the TV probe.
7.2.4.1 Vagina
The most common location for vaginal DIE is the posterior vaginal fornix, just posterior to the lower lip of the cervix. Vaginal DIE nodules are avascular and have an echogenicity similar to that of the normal vaginal wall mucosa. Vaginal DIE nodules usually protrude from the posterior vaginal mucosal wall into the vaginal cavity (Fig. 7.4a, b). E-TVS techniques such as gel or saline SVG may be performed, which allows for improved visualization of the lesion and its borders. Vaginal DIE lesions may also be associated with concurrent anterior rectal DIE (Fig. 7.4c), causing obliteration of the RVS and POD.
Fig. 7.4
A deep infiltrating endometriosis (DIE) nodule (*) is visualized in the posterior vaginal fornix (PVF) with gel sonovaginography in the sagittal (a) and transverse (b) planes. In (c), a vaginal DIE nodule (*) extends posteriorly into the rectovaginal septum. An anterior rectum DIE (**) nodule is also present and adherent to the vaginal nodule. POD pouch of Douglas
7.2.4.2 Rectovaginal Septum
The RVS is located between the anterior rectum and posterior vaginal wall and extends along the lower two-thirds posterior vaginal wall (please note the cephalic border of the RVS on TVS is at the level of the inferior margin of the posterior cervix). RVS DIE usually occurs as an extension of other DIE lesions (i.e. from the anterior rectum and/or posterior vaginal wall) and is not though to occur as a solitary lesion within the RVS. On TVS, the RVS appears as a thin hyperechoic line between the posterior vaginal mucosa and anterior rectum and can be visualized in both the transverse and the sagittal plane (Fig. 7.5). DIE infiltration of the RVS is suspected when the normally thin RVS appears thickened and irregular. The borders of the RVS may also become indistinguishable in cases of RVS infiltration from neighbouring structures.
