The posterior compartment is the most common site of DE.28 The ultrasound operator may use the opportunity of the probe entering the vagina to visualize the retroperitoneal aspect of the rectum and RVS to the level of the rectouterine pouch (See Figure 6). When there is fluid in the rectouterine pouch, the boundary of the retro- and intraperitoneal rectum and the most superior aspect of the RVS are easier to visualize (See Figure 7). At the maximum insertion depth, when the probe is positioned posterior to the cervix, the PVF can be appreciated as the hypoechoic layer in direct contact with the probe. A sweep from one side to the other should be done to observe the entire posterior vagina (See Video 5).
DE of the retroperitoneal rectum or RVS is rare, but when present, you should note whether the lesion lies within one specific anatomic area or extends between areas (e.g. lesions may extend from the vagina to the rectum through the RVS). DE of the PVF is characterized by significant and focal thickening of the vagina and sometimes can be distinguished from the surrounding normal vagina by its slight hypoechoic nature (See Figure 8 online). Clinicians should always directly visualize the vagina on speculum examination. Ultrasound operators should assess the proximity of another normal or abnormal anatomical structure to the PVF DE. The rectum is very close and may be tethered, even when not directly affected by DE itself (See Video 6). If surgical excision is planned, it may be prudent to measure the distance between the PVF DE and the closest aspect of the rectum.
DE of the bowel generally occurs in the muscularis externa layer and does not infiltrate through to the mucosa (Figures 9 through 12, Video 7). A normal bowel wall is depicted in Video 8. The anterior rectum, which begins after the bowel transitions from retroperitoneal to intraperitoneal, is the most common site of DE in the bowel.
It is possible, although more challenging, to visualize rectosigmoid junction or sigmoid colon DE because of the physical distance between the probe and the disease. The goal is to follow the bowel wall as long as possible. When DE is noted, the IDEA consensus suggests six unique characteristics,14 which should be routinely considered. The distance from the lowest nodule to the anal verge should be measured to assist in surgical planning as the type and location of bowel surgery has implications on surgical risk.29
The USLs are one of the most common sites for DE.28 Recently, it has become apparent that the normal USLs are quite easy to visualize on TVS (See Figure 13. We have published an approach to visualization, which is Free Access,30 and a proposed nomenclature system for DE that involves the USLs.31 One essential step is understanding the normal appearance and thickness of the rectouterine pouch peritoneum (See Video 9). DE involving the USLs may infiltrate the parametrium, the PVF, or the torus uterinus, which is defined as the transverse thickening that binds the USLs along the posterior cervix. In most cases, USL DE is confined to the USLs (Figures 14 and 15, but there are often associated adhesions, resulting in ovarian fixation or rectouterine pouch obliteration (See Video 3, Video 10, and Video 11).
Bladder DE is rare (See Figure 16), but the bladder should always be assessed because it is so simple to do. Place the ultrasound probe in the anterior vaginal fornix and swing side-to-side, visualizing the muscularis layer for focal thickening and hypoechoic changes. Similarly, intrinsic ureteral endometriosis is rare. DE of the USLs infiltrating the parametrium may extrinsically compress the ureter leading to hydroureter and hydronephrosis (See Video 12). Even when not extrinsically compressed, the ureters may be kinked due to adjacent DE, and so, the ureters should be evaluated in all patients and it is easy to learn how to do so.32,33 It may be appropriate to evaluate the kidneys for hydronephrosis in all patients in whom endometriosis is a concern, although we restrict this particular add-on ultrasound to those with demonstrable hydroureter and/or large USL/parametrial DE nodules.
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- Adamson GD, Kennedy S, Hummelshoj L. Creating solutions in endometriosis: Global collaboration through the World Endometriosis Research Foundation. J Endometr. 2010;2:3-6.
- Leonardi M, Singh SS, Murji A, et al. Deep endometriosis: a diagnostic dilemma with significant surgical consequences. J Obstet Gynaecol Canada. 2018;40:1198-1203.
- Leyland N, Casper R, Laberge P, et al. Endometriosis: diagnosis and management. J Obstet Gynaecol Canada. 2010;32:S1-S28.
- American College of Obstetricians and Gynecologists. Practice Bulletin No. 114: Management of Endometriosis. Obstet Gynecol. 2010;116:223-236.
- Agarwal SK, Chapron C, Giudice LC, et al. Clinical diagnosis of endometriosis: a call to action. Am J Obstet Gynecol. 2019;220:354.e1-354.e12.
- Kho KA, Shields JK. Diagnosis and management of primary dysmenorrhea. JAMA. 2019;344:1-2.
- Benacerraf BR, Groszmann Y. Sonography should be the first imaging examination done to evaluate patients with suspected endometriosis. J Ultrasound Med. 2012;31:651-653.
- Somigliana E, Vercellini P, Vigano’ P, Benaglia L, Crosignani PG, Fedele L. Non-invasive diagnosis of endometriosis: The goal or own goal? Hum Reprod. 2010;25:1863-1868.
- Singh SS, Suen MWH. Surgery for endometriosis: beyond medical therapies. Fertil Steril. 2017;107:549-554.
- Menakaya UA, Rombauts L, Johnson NP. Diagnostic laparoscopy in pre-surgical planning for higher stage endometriosis: Is it still relevant? Aust New Zeal J Obstet Gynaecol. 2016;56:518-522.
- Nisenblat V, Bossuyt PMM, Farquhar C, Johnson N, Hull ML. Imaging modalities for the non-invasive diagnosis of endometriosis. Cochrane Database Syst Rev. 2016:Art. No.: CD009591. DOI: 10.1002/14651858.CD009591.
- AIUM Practice Guideline for the Performance of Ultrasound of the Female Pelvis. J Ultrasound Med. 2014;33:1122-1130.
- Guerriero S, Condous G, van den Bosch T, et al. Systematic approach to sonographic evaluation of the pelvis in women with suspected endometriosis, including terms, definitions and measurements: a consensus opinion from the International Deep Endometriosis Analysis (IDEA) group. Ultrasound Obstet Gynecol. 2016;48:318-332.
- Reid S, Lu C, Casikar I, et al. Prediction of pouch of Douglas obliteration in women with suspected endometriosis using a new real-time dynamic transvaginal ultrasound technique: the sliding sign. Ultrasound Obstet Gynecol. 2013;41:685-691.
- Gerges B, Lu C, Reid S, Chou D, Chang T, Condous G. Sonographic evaluation of immobility of normal and endometriotic ovary in detection of deep endometriosis. Ultrasound Obstet Gynecol. 2017;49:793-798.
- Tompsett J, Leonardi M, Gerges B, et al. Ultrasound-based endometriosis staging system: validation study to predict complexity of laparoscopic surgery. J Minim Invasive Gynecol. 2019;26:477-483.
- Collins BG, Ankola A, Gola S, McGillen KL. Transvaginal US of endometriosis: looking beyond the endometrioma with a dedicated protocol. RadioGraphics. 2019;39:1549-1568.
- National Institute for Health and Care Excellent. Endometriosis: Diagnosis and Management.; 2017. nice.org.uk/guidance/ng73.
- Leonardi M, Condous G. How to perform an ultrasound to diagnose endometriosis. Australas J Ultrasound Med. 2018;21:61-69.
- Young SW, Groszmann Y, Dahiya N, et al. Sonographer-acquired ultrasound protocol for deep endometriosis. Abdom Radiol. 2019.
- Timmerman D, Valentin L, Bourne TH, Collins WP, Verrelst H, Vergote I. Terms, definitions and measurements to describe the sonographic features of adnexal tumors: a consensus opinion from the International Ovarian Tumor Analysis (IOTA) group. Ultrasound Obstet Gynecol. 2000;16:500-505.
- Van Holsbeke C, Van Calster B, Guerriero S, et al. Endometriomas: Their ultrasound characteristics. Ultrasound Obstet Gynecol. 2010;35:730-740.
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- Khan MAS, Ang CW, Hakeem AR, Scott N, Saunders RN, Botterill I. The impact of tumour distance from the anal verge on clinical management and outcomes in patients having a curative resection for rectal cancer. J Gastrointest Surg. 2017;21:2056-2065.
- Leonardi M, Condous G. A pictorial guide to the ultrasound identification and assessment of uterosacral ligaments in women with potential endometriosis. Australas J Ultrasound Med. 2019;22:157-164.
- Leonardi M, Martins WP, Espada M, Arianayagam M, Condous G. A proposed technique to visualize and classify uterosacral ligament deep endometriosis with and without infiltration into the parametrium or torus uterinus. Ultrasound Obstet Gynecol. April 2019:uog.20300.
- Bean E, Naftalin J, Jurkovic D. How to assess the ureters during pelvic ultrasound. Ultrasound Obstet Gynecol. 2018.
- Aas-Eng K, Salama M, Sevelda U, Ruesch C, Nemeth Z, Hudelist G. Learning curve for detection of the distal part of ureters by transvaginal sonography (TVS): a feasibility study. Ultrasound Obstet Gynecol. June 2019.
- Khong SY, Bignardi T, Luscombe G, Lam A. Is pouch of Douglas obliteration a marker of bowel endometriosis? J Minim Invasive Gynecol. 2011;18:333-337.
- Robinson AJ, Rombauts L, Ades A, Leong K, Paul E, Piessens S. Poor sensitivity of transvaginal ultrasound markers in diagnosis of superficial endometriosis of the uterosacral ligaments. J Endometr Pelvic Pain Disord. 2018;10:10-17.
- Reid S, Leonardi M, Lu C, Condous G. The association between ultrasound-based ‘soft markers’ and endometriosis type/location: A prospective observational study. Eur J Obstet Gynecol Reprod Biol. 2019;234:171-178.
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- Leonardi M, Espada M, Lu C, Stamatopoulos N, Condous G. A novel ultrasound technique called saline infusion sonoPODography to visualize and understand the pouch of Douglas and posterior compartment contents: A Feasibility Study. J Ultrasound Med. 2019;38:3301-3309.