Abstract
Endometriosis is a common gynaecological problem, affecting approximately 5 per cent of women . The diagnosis can take many years and the condition can cause debilitating pain and infertility. The disease can be found in many sites throughout the pelvis, in particular the ovaries, pelvic peritoneum, pouch of Douglas (POD), rectum, rectosigmoid, rectovaginal septum (RVS), uterosacral ligaments (USLs), vagina and urinary bladder. Mapping of deeply infiltrating disease is essential to enable the correct counselling regarding treatment modalities (medical or surgical) and risks of surgery, triaging to the correct surgical centre, informing the surgeon in order to correctly plan surgery and enabling other specialities, such as colorectal or urology support, to be organized in advance. Magnetic resonance imaging (MRI) has been used as the main pre-operative imaging modality, but with the correct training and experience transvaginal ultrasound can perform the same role .
Introduction
Endometriosis is a common gynaecological problem, affecting approximately 5 per cent of women [1]. The diagnosis can take many years [2] and the condition can cause debilitating pain and infertility. The disease can be found in many sites throughout the pelvis, in particular the ovaries, pelvic peritoneum, pouch of Douglas (POD), rectum, rectosigmoid, rectovaginal septum (RVS), uterosacral ligaments (USLs), vagina and urinary bladder. Mapping of deeply infiltrating disease is essential to enable the correct counselling regarding treatment modalities (medical or surgical) and risks of surgery, triaging to the correct surgical centre, informing the surgeon in order to correctly plan surgery and enabling other specialities, such as colorectal or urology support, to be organized in advance. Magnetic resonance imaging (MRI) has been used as the main pre-operative imaging modality, but with the correct training and experience transvaginal ultrasound can perform the same role [3]. Vaginal digital examination has been shown to be inferior diagnostically to transvaginal scanning (TVS) [4].
Before undertaking any ultrasound examination it is vital to first assess and clearly document the symptoms that have led to the examination. The history should include general gynaecological history and features specific to endometriosis, including: parity; menstrual period; previous surgery including laparoscopic or open; family history of endometriosis; previous non-surgical treatment for endometriosis (type, duration, effect); subfertility including duration; treatment for infertility and outcome of fertility treatment; pain (dysmenorrhoea, dyspareunia, dysuria, dyschezia, non-cyclic pelvic pain). The onset and duration of symptoms should be noted and the intensity of the pain symptoms should be objectively assessed using a 1–10 visual analogue score. Cyclic haematochezia and/or haematuria associated with menstruation are of particular significance.
Transvaginal Ultrasound Examination
A systematic approach to thoroughly assessing all the pelvic organs is necessary and should be followed for all patients with suspected endometriosis. It is helpful to ask women to empty their bladder before starting the examination so that the bladder is empty or minimally filled.
First, the uterus should be assessed in the transverse and sagittal planes, paying particular attention to the features of adenomyosis [5,6]. Next, the adnexa are assessed; the ovaries are found and their size measured in three orthogonal planes. Ovarian cysts are diagnosed as endometriomas when they appear as well-circumscribed, thick-walled cysts that contain low-level, homogeneous internal echoes (‘ground glass’) [7] (Figure 9.1). Measurements are recorded from the inside of the cyst wall in three orthogonal planes. The adnexa are also systematically examined for the presence of tubal dilation and, if present, the type of fluid should be documented, as haematosalpinx is often found with severe disease.
Ovarian mobility is important and can be assessed by a combination of gentle pressure with the vaginal probe and abdominal pressure with the examiner’s free hand, as in a bimanual examination. The ovary is deemed to be completely free when all of its borders can be seen sliding across the surrounding structures. Ovarian adhesions can be identified as the inability to slide the ovary against its surrounding structures. Ovarian endometriomas are almost always associated with adhesions, and this should be documented clearly [8] (Figure 9.2).
Figure 9.2 Transvaginal scan of a patient with extensive pelvic endometriosis. The ovary is adherent to the posterior aspect of the uterus and there is no mobility of the structures when pressure is applied via the ultrasound transducer. There are thick, hyperechoic plaques (thin arrow) which further raise suspicion of a frozen pelvis. The ovary is also distended by an endometrioma (large arrow).
If the tubes are dilated, their mobility should be documented in a similar fashion. Normal fallopian tubes are difficult to identify in the absence of background fluid in the pelvis. It is difficult to see filmy adhesions on TVS unless there is fluid entrapped within the adhesions, giving rise to the ‘flapping sail sign’ [9] and peritoneal pseudocysts.
Anterior Pelvic Structures
The probe is positioned in the anterior vaginal fornix. It should be possible to gently push the bladder away from the anterior aspect of the uterus. If the bladder cannot be separated from the uterus with ease, this should raise the suspicion of adhesions between the bladder and uterus (more common after Caesarean section) which may be due to endometriosis in this location. The bladder should be examined throughout in the sagittal plane. The presence of a hypoechoic or isoechoic thickening (nodule) of the bladder wall or a nodule with a heterogeneous echotexture containing numerous anechoic (‘bubble-like’) areas within the bladder wall is considered indicative of bladder endometriosis [10]. This is normally located where the bladder comes into contact with the uterus, but bladder dome endometriosis is also possible (Figure 9.3).
Figure 9.3 Transvaginal scan of an endometriotic bladder nodule. (a) sagittal section, (b) transverse view. Moderately filled bladder allows for good visualization of the bladder wall. The cervix is located to the right of the screen (star). The endometriotic nodule (arrows) indenting the bladder wall is hypoechogenic ((a) and (b)) or hyperechoic ((c), callipers). Cystoscopy and a biopsy may be needed to exclude bladder malignancy.
Ureteric and Renal Assessment
Endometriosis can, in very severe cases, involve the ureter and cause ureteric stenosis, hydroureter and eventually hydronephrosis. For this reason, the ureters should be routinely examined. It is possible to visualize the ureters in the following way, which is a modification of the technique first described by Pateman et al. in 2013 [11]. The urethra is found in the mid-sagittal plane. The probe is then moved laterally until the ureteral meatus can be seen as a ridge in the internal wall of the bladder. The intravesical portion of the ureter can then be followed until it exits the bladder at the vesico-ureteric junction. The extravesical ureter can then be followed caudally until it reaches the iliac vessels. If severe endometriosis is suspected, it is important to wait for peristalsis as this confirms ureteric patency [12]. Any evidence of ureteric dilation, abnormal bending or discrepancy in peristalsis frequency should raise the suspicion of a stricture. In women with evidence of partial (Figure 9.4) and complete (Figure 9.5) ureteric obstruction, the distance from the stricture to the ureteric orifice should be measured (Figure 9.6).
