(1)
Department of Fetal Medicine and Obstetric & Gynecological Ultrasound, Manipal Hospital, Bangalore, Karnataka, India
Endometriosis is the presence of ectopic endometrial glands and stroma (basically endometrial tissue) seen outside of the uterus.
This is commonly seen in women belonging to the reproductive age group, who present with symptoms such as dysmenorrhoea, chronic pelvic pain and subfertility/infertility. Women, however, may be asymptomatic, and endometriosis may be incidentally diagnosed on an ultrasound or during laparoscopy.
Endometriosis is seen in about 4–13 % of women of the reproductive age and in 25–50 % of women with infertility.
Endometriotic lesions could be superficial or deep (more than 5 mm from the peritoneal surface). Based on their location, they can be grouped into three categories:
- 1.
Ovaries and pelvic peritoneum: This is the most common site. It is important to note that tiny superficial endometriotic lesions of the pelvic peritoneum or on the ovarian surface (i.e., the gunshot or powder-burn lesions seen on laparoscopy), cannot be picked up on ultrasound.
- 2.
Deep infiltrating endometriosis of the pelvis: This is seen in 15–30 % of women with endometriosis. Lesions (endometrial tissue) penetrate into the retroperitoneal space or the walls of the pelvic organs, to a depth of at least 5 mm. Common locations are the uterosacral, rectosigmoid, vagina, bladder and ureter.
- 3.
Extra-pelvic endometriosis: This is endometriosis seen outside the pelvis, involving the abdominal wall, lungs, etc.
Please note: Endometriomas of the ovary have been discussed in detail in the chapter on ovarian masses (Chap. 7).
8.1 Deep Infiltrating Endometriosis (DIE)
Here, the lesions (endometrial tissue) penetrate into the retroperitoneal space and/or the walls of the pelvic organs to a depth of at least 5 mm. Common locations are the uterosacral, rectosigmoid, vagina, bladder, ureter, etc. This is seen in 15–30 % of women with endometriosis.
8.1.1 Significance of DIE
DIE causes pain which can be very distressing. The paincould be in the form of dysmenorrhoea, dyspareunia, chronic pelvic pain or bladder and bowel symptoms like dysuria and painful defecation.
DIE is often not diagnosed on ultrasound as visualizing and detecting these lesions requires high suspicion and knowledge of the spectrum of DIE.
DIE can affect the pelvic organs by either by primary involvement or by secondary involvement, caused by anatomic distortion of a structure due to fibrotic retraction of an adjoining DIE nodule. This can lead to complications such as hydronephrosis.
DIE nodules have the potential to undergo malignant transformation.
In pregnancy, they can increase in size and vascularity and may become painful or affect pelvic organs for the first time, in pregnancy.
Diagnosing DIE is very important for optimal planning of surgery. If DIE is anticipated, appropriate consent can be taken from the patient, and the primary surgeon may decide to involve a colorectal surgeon or urologist.
Fig. 8.1
Bowel DIE. Longitudinal section and transverse section of a DIE nodule (short arrows) involving the anterior rectal wall. The nodule is hypoechoic with diffuse borders. On LS, the normal anterior rectal muscularis above the lesion shows a fine hyperechoic line within, which separates the outer longitudinal from the inner circular muscular layer (long arrow). On TS, the nodule shows acoustic shadowing suggestive of fibrotic elements within the DIE nodule. TS of the bowel gives a ‘signet-ring’ appearance because of the nodule in one part of the bowel wall with normal muscularis (long arrow) seen all around the bowel wall
Fig. 8.2
DIE lesion (arrow) showing poor vascularity on Doppler
Transvaginal scan is the diagnostic modality of choice.
DIE lesions are usually fusiform or nodular in shape.
The lesions appear hypoechoic.
They have diffuse borders.
They are firm and may show some amount of acoustic shadowing.
They are typically solid but could be solid and cystic, or only cystic.
They are most often poorly vascularised.
They are generally tender and therefore a pain/tenderness-guided approach during TVS is useful in locating them.
They are multiple in about 20 % of causes.
In some cases, where the ovaries appear normal on scan, these DIE nodules are not suspected and therefore more likely to be missed.
For the diagnosis of DIE, other diagnostic modalities like MRI, CT and barium studies can also be resorted to. However, transvaginal scan is the modality of choice because it is the least expensive, least invasive and has a sensitivity of 81.1 % and a specificity of 94.2 % (Vimercati et al. 2012). This high specificity and sensitivity is because transvaginal scan is dynamic and interactive, allowing evaluation of tenderness and adhesions, in addition to having a high resolution.
8.1.2 DIE of Large Bowel (Rectosigmoid)
This primarily involves the anterior muscularis of the rectosigmoid. The anterior muscularis of the rectum can be traced just behind the vagina and along the posterior wall of the uterus. There is a fine white line which is seen within it that divides the anterior muscularis into an inner layer of circular muscle fibres and an outer layer of longitudinal muscle fibres. Just within the muscularis lies the hyperechoic submucosa. Within the submucosa is the dark central linear area, which is the lumen of the large bowel. Patients with endometriosis of the bowel may be asymptomatic or may complain of dysmenorrhoea, painful defecation or mucoid/bloody rectal discharge during periods.
Fig. 8.3
DIE nodule (traced) is seen involving the anterior rectal wall. The nodule was seen in the POD, adherent to the posterior wall of the uterus and the right ovary
Fig. 8.4
Rectosigmoid DIE in a 32-year-old lady who complained of severe pain in the rectal region with mucoid discharge per rectum during periods. Colonoscopy and ultrasound scans done elsewhere were reported as normal. (a) The anterior muscularis of the bowel loop is much thicker than the posterior muscularis in the area of the DIE nodule. Just within the muscularis, the hyperechoic submucosa (short arrows) is seen, and within that is a dark linear area, which is the central lumen of the bowel (long arrow). (b) TS and LS view of the DIE nodule. Typical ‘signet ring’ appearance is noted on TS, (c) DIE nodule showing moderate to high vascularity. (d, e) Both ovaries appeared normal
Fig. 8.5
(a, b) ‘Red Indian hair dress’ sign seen in two different cases of bowel DIE. The images show hyperechoic linear echoes (arrows) radiating out from the DIE nodule resembling a ‘Red Indian hairdo’. This typical feature is prominent on ultrasound and is therefore helpful in picking up DIE lesions
Fusiform-shaped lesions along the anterior muscularis of the large bowel. The typical appearance (thin hyperechoic line) of the bowel muscularis in that area is lost but can be seen above and below it.
The affected anterior muscularis of the bowel loop with DIE is much thicker than the corresponding posterior muscularis.
On a longitudinal section, they appear as thickened areas of the anterior muscularis, and on cross section, the bowel gives a ‘signet ring’ appearance.
At times, one may see hyperechoic linear echoes radiating out of a DIE nodule, giving it a ‘Red Indian hairdo’ appearance from which it derives the term ‘Red Indian hair dress’ sign. This appearance is because of the involvement of the bowel submucosa due to fibrotic retraction by the DIE nodule. This typical feature is prominent on ultrasound and is therefore helpful in picking up DIE lesions.
Lesions that are seen beyond the uterine fundus are generally considered to be involving the sigmoid, while those below the uterine fundus are considered to be rectal, though it is not possible to have a clear-cut delineation of the rectosigmoid junction on ultrasound.
One should measure the distance between the lower end of the nodule and the anal verge, because lesions that are less than 7 cm from the anal verge are more difficult to manage surgically than those which are higher up.
The DIE nodules are most often adherent to the posterior wall of the uterus, because of which there is an absence of the sliding sign (bowels sliding along the posterior wall of the uterus and vaginal fornix). This absent sliding sign has a high LR of 23.6 for rectal DIE (Hudelist et al. 2013).
Transvaginal scan has a very high pickup for rectosigmoid endometriosis (sensitivity of 91 % and specificity of 98 %). For lesions that are high up in the sigmoid (beyond the reach of a transvaginal scan), a double contrast barium enema may be useful.
8.1.3 DIE of the Vaginal Wall
DIE can also involve the walls of the vagina, commonly the posterior wall and very often in continuity with rectal DIE, forming a rectovaginal DIE lesion. Patients can be asymptomatic or complain of dysmenorrhoea or dyspareunia. If the adjoining bowel is involved, then the patient may present with rectal symptoms.
Fig. 8.6
Vaginal DIE: (a) Longitudinal section of the posterior fornix. The probe in this image is in the posterior fornix with the cervix (CX) lying anteriorly and the posterior vaginal wall with the hypoechoic DIE nodule posteriorly (small arrows). (b) Longitudinal section of the anterior fornix (in this image the probe is in the anterior fornix), showing normal anterior vaginal walls (long arrow)
Fig. 8.7
Rectovaginal DIE: (a) Longitudinal section of posterior fornix showing a hypoechoic, thickened DIE lesion of the vagina and rectum. The normal rectovaginal septum between the normal rectum and vagina is seen as a hyperechoic line (short arrow). There is a breach in the upper part of the RV septum (long arrow) where the rectal DIE and the vaginal DIEs are continuous. (b) The rectovaginal DIE was also seen on TAS. The image shows a TS of the cervix (CX), thickened vaginal wall with the DIE lesion (long arrow) and the rectal DIE (short arrow). The two DIE lesions with their communication form an ‘hourglass’ lesion
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