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

The IDEA (International Deep Endometriosis Analysis group) statement is a consensus opinion on terms, definitions and measurements that may be used to describe the sonographic features of the different phenotypes of endometriosis. Currently, it is difficult to compare results between published studies because authors use different terms when describing the same structures and anatomical locations. We hope that the terms and definitions suggested herein will be adopted in centers around the world. This would result in consistent use of nomenclature when describing the ultrasound location and extent of endometriosis. We believe that the standardization of terminology will allow meaningful comparisons between future studies in women with an ultrasound diagnosis of endometriosis and should facilitate multicenter research. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd. Enfoque sistemático para la evaluación ecográfica de la pelvis en mujeres con posible endometriosis, incluyendo términos, definiciones y mediciones: una opinión consensuada del Grupo Internacional de Análisis de la Endometriosis Profunda La declaración del Grupo Internacional de Análisis de la Endometriosis Profunda (IDEA, por sus siglas en inglés) es una opinión basada en un consenso sobre los términos, definiciones y medidas que se pueden utilizar para describir las características ecográficas de los distintos fenotipos de la endometriosis. Actualmente es difícil comparar los resultados entre los estudios publicados porque los autores utilizan términos diferentes para describir las mismas estructuras y localizaciones anatómicas. Esperamos que los términos y definiciones propuestas en este documento se adopten en centros de investigación de todo el mundo. Esto resultaría en un uso uniforme de la nomenclatura para describir la ubicación y el alcance de la endometriosis en la evaluación ecográfica. Creemos que la normalización de la terminología permitirá realizar comparaciones significativas entre futuros estudios de mujeres con diagnóstico de endometriosis mediante ecografía y debería facilitar la investigación entre múltiples centros de investigación. Endometriosis is a common gynecological problem, affecting approximately 5% of women1. 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. Correct site-specific diagnosis is fundamental in defining the optimal treatment strategy for endometriosis. Non-invasive imaging methods are required to map accurately the location and extent of endometriotic lesions. The recent consensus statement produced by the World Endometriosis Society recommended the establishment of centers of expertise for the management of higher-stage disease2. This recommendation requires a reliable preoperative system of triage which enables immediate understanding of the location and severity of disease. Increasingly, endometriosis is being managed medically and surgery can be avoided or delayed in a growing proportion of cases. Transvaginal sonography (TVS) is the first-line imaging technique in the diagnosis of pelvic endometriosis and in particular for deep infiltrating endometriosis (DIE)3. It is important to note, however, that there is substantial heterogeneity in the reported sensitivity and specificity of TVS with regard to detection of DIE, irrespective of its location4, 5. Adding ultrasound examination by an experienced operator to history and pelvic examination improves the accuracy of diagnosis of pelvic endometriosis6, 7. In their meta-analysis, Hudelist et al.8 concluded that TVS with or without the use of prior bowel preparation is an accurate test for non-invasive, presurgical detection of DIE of the rectosigmoid. Although the diagnostic performance of ultrasound for detecting DIE reported by individual units is excellent for certain anatomical locations9-11, the lack of standardized definitions in the sonographic classification and diagnosis of DIE is a general cause for concern. This lack of uniformity when classifying anatomical location and extent of disease contributes to the considerable variation in the reported diagnostic accuracy of TVS in the diagnosis of endometriosis. The aim of this consensus opinion is to ensure that the ultrasound examination of a woman with potentially underlying endometriosis is performed in a standardized manner, that the measurement of endometriotic lesions is standardized and that the terminology used when describing the location of DIE and the sonographic features of DIE and other manifestations of endometriosis (endometriomas, adenomyosis, pelvic adhesions) is uniform. This consensus opinion should be useful in clinical practice as well as in research. We believe that careful definition of ultrasound-detected DIE will facilitate interpretation of research and lead to improved clinical care. This work is based on the opinion of a panel of clinicians, gynecological sonologists, advanced laparoscopic surgeons and radiologists (International Deep Endometriosis Analysis (IDEA) group) with expertise in diagnosis and management of endometriosis. Criteria used to invite the experts to participate in this consensus process included their having significant peer-reviewed publications in the field of diagnosis and management of endometriosis. An initial statement was presented in 2011 at the ISUOG congress in Copenhagen12, incorporating several suggestions from all participants. A first draft was written in December 2014 by a joint effort of the two first authors (S.G. and G.C.) and sent to all coauthors. All coauthors had the opportunity to comment within a fixed time limit. Reply was mandatory for coauthorship. Taking all comments into account, a revised draft was then sent to all coauthors. In case of conflicting opinions, a consensus was proposed after discussion between the two first authors and the last author (D.T.). This pathway was repeated until a consensus between all authors was reached. The consensus also included ultrasound images/videos and schematic drawings to illustrate the text. After 13 revisions, the manuscript was deemed ready for submission. In addition to terms, definitions and measurements to describe the sonographic features of DIE, adhesions, adenomyosis and endometriomas, this consensus opinion includes recommendations regarding how to take a history, how to perform a clinical examination, how to perform an ultrasound examination and which ultrasound modality to use when examining patients with suspected or known endometriosis. DIE anatomical locations in this consensus were modified from Chapron's anatomical distribution of pelvic DIE13. A detailed clinical history should be taken for all women with suspected endometriosis, with particular emphasis on symptoms which could be attributed to endometriosis14, 15. The following should be noted specifically: age; height; weight; ethnic origin; parity; bleeding pattern (regular, irregular or absent); last menstrual period; previous surgery for endometriosis (type, effect); previous myomectomy or Cesarean delivery (these entail increased risk of DIE in the bladder); family history of endometriosis; previous non-surgical treatment for endometriosis (type, duration, effect); subfertility including duration of subfertility; treatment for infertility and outcome of fertility treatment; pain (dysmenorrhea, dyspareunia, dysuria, dyschezia, chronic pelvic pain); hematochezia and/or hematuria. The onset and duration of symptoms should be noted and, if possible, the intensity of the pain recorded by letting the patient use a visual analog scale or investigating it with a 0–10 narrative numeric rating scale. A pelvic examination should be performed either before or after the pelvic ultrasound scan, with the aim of defining the presence or absence of vaginal and/or low rectal endometriosis7. The pelvic examination should include speculum examination (direct visualization of vaginal or cervical DIE) and vaginal palpation. Mobility, fixation and/or tenderness of the uterus should be evaluated carefully. Site-specific tenderness in the pelvis should also be evaluated. The purpose of performing an ultrasound examination in a woman with suspected endometriosis is to try to explain underlying symptoms, map the disease location and assess the severity of disease prior to medical therapy or surgical intervention. Various ultrasound approaches have been published, but to date none has been externally validated16, 17. We propose four basic sonographic steps when examining women with suspected or known endometriosis, as shown in Figure 1. Note that these steps can be adopted in this or any order as long as ALL four steps are performed to confirm/exclude the different forms of endometriosis. Using TVS as the first-line imaging tool, the operator should examine the uterus and the adnexa. The mobility of the uterus should be evaluated: normal, reduced or fixed (‘question mark sign’)18. Sonographic signs of adenomyosis should be searched for and described using the terms and definitions published in the Morphological Uterus Sonographic Assessment consensus opinion19. The presence or absence of endometriomas (Figure S1a), their size, measured systematically in three orthogonal planes (see ‘Measurement of lesions’, below), the number of endometriomas and their ultrasound appearance should be noted20. The sonographic characteristics of any endometrioma should be described using the International Ovarian Tumor Analysis terminology21. An atypical endometrioma (Figure S1b) is defined as a unilocular-solid mass with ground glass echogenicity with a papillary projection, a color score of 1 or 2 and no flow inside the papillary projection20. Ovarian endometriomas are associated frequently with other endometriotic lesions, such as adhesions and DIE22, 23. The ‘kissing’ ovaries sign (Figure S2) suggests that there are severe pelvic adhesions; bowel and Fallopian tube endometriosis are significantly more frequent in women with kissing ovaries vs those without kissing ovaries: 18.5% vs 2.5% and 92.6% vs 33%, respectively24. Endometriomas may undergo decidualization in pregnancy, in which case they can be confused with an ovarian malignancy on ultrasound examination (Figure S3)25. Simultaneous presence of other endometriotic lesions may facilitate a correct diagnosis of endometrioma in pregnancy and minimize the risk of unnecessary surgery. The second step is to search for sonographic ‘soft markers’, i.e. site-specific tenderness (SST) and fixed ovaries. The presence of soft markers increases the likelihood of superficial endometriosis and adhesions26, 27. By applying pressure between the uterus and ovary, one can assess if the ovary is fixed to the uterus medially, to the pelvic side wall laterally or to the USLs. The presence of adhesions can also be suspected if, on palpation with the probe and/or abdominal palpation with the free hand, the ovaries or the uterus appear to be fixed to adjacent structures (broad ligament, POD, bladder, rectum and/or parietal peritoneum). If there is pelvic fluid, fine strands of tissue (adhesions) may be seen between the ovary (with or without endometrioma) and the uterus or the peritoneum of the POD27-30. If there are endometriomas or pelvic endometriosis, the Fallopian tubes are frequently involved in the disease process. Adhesions may distort the normal Fallopian tubal course and occlusion of the Fallopian tube(s) by endometriotic foci or distal tubular adhesions may also occur. As a consequence, a sactosalpinx may develop. For these reasons, hydrosalpinx/hematosalpinx and peritoneal cysts should be searched for and reported. The third step is to assess the status of the POD using the real-time TVS-based ‘sliding sign’. In order to assess the sliding sign when the uterus is anteverted (Figure 2a), gentle pressure is placed against the cervix using the transvaginal probe, to establish whether the anterior rectum glides freely across the posterior aspect of the cervix (retrocervical region) and posterior vaginal wall. If the anterior rectal wall does so, the ‘sliding sign’ is considered positive for this location (Videoclip S1a). The examiner then places one hand over the woman's lower anterior abdominal wall in order to ballot the uterus between the palpating hand and the transvaginal probe (which is held in the other hand), to assess whether the anterior bowel glides freely over the posterior aspect of the upper uterus/fundus. If it does so, the sliding sign is also considered positive in this region (Videoclip S1b). When the sliding sign is found to be positive in both of these anatomical regions (retrocervix and posterior uterine fundus), the POD is recorded as being not obliterated. If on TVS it is demonstrated that either the anterior rectal wall or the anterior sigmoid wall does not glide smoothly over the retrocervix or the posterior uterine fundus, respectively, i.e. at least one of the locations has a negative sliding sign, then the POD is recorded as obliterated31, 32. Demonstrating and describing the real-time ultrasound-based sliding sign in a retroverted uterus is different (Figure 2b). Gentle pressure is placed against the posterior upper uterine fundus with the transvaginal probe, to establish whether the anterior rectum glides freely across the posterior upper uterine fundus. If the anterior rectum does so, the sliding sign is considered to be positive for this location (Videoclip S2a). The examiner then places one hand over the woman's lower anterior abdominal wall in order to ballot the uterus between the palpating hand and transvaginal probe (which is held in the other hand), to assess whether the anterior sigmoid glides freely over the anterior lower uterine segment. If it does so, the sliding sign is also considered to be positive in this region (Videoclip S2b). As long as the sliding sign is found to be positive in both of these anatomical regions (i.e. the posterior uterine fundus and the anterior lower uterine segment), the POD is recorded as non-obliterated33. The fourth step is to search for DIE nodules in the anterior and posterior compartments. To assess the anterior compartment, the transducer is positioned in the anterior fornix of the vagina. If bladder endometriosis is suspected on the basis of symptoms, patients should be asked not to empty their bladder completely before the ultrasound examination. A slightly filled bladder facilitates evaluation of the walls of the bladder and detection and description of endometriotic nodules. Finally, the transducer is positioned in the posterior fornix of the vagina and slowly withdrawn through the vagina to allow visualization of the posterior compartment. Some authors advocate the use of bowel preparation on the evening before the pelvic scan and the use of a rectal enema within an hour before the ultrasound examination to eliminate fecal residue and gas in the rectosigmoid34-37. However, this is not mandatory, and there are no published prospective studies comparing TVS with and without bowel preparation for the diagnosis of bowel DIE. In a recent meta-analysis, TVS, either with or without bowel preparation, was found to be an accurate predictor of rectosigmoid DIE8. The anterior compartment includes the following anatomical locations: urinary bladder, uterovesical region and ureters. Bladder DIE occurs more frequently in the bladder base and bladder dome than in the extra-abdominal bladder (Videoclip S3)38. The bladder is best scanned if it contains a small amount of urine because this reduces false-negative findings. Although Savelli et al.38 described two zones (bladder base and dome), we propose dividing the bladder ultrasound assessment into four zones (Figure 3): (i) the trigonal zone, which lies within 3 cm of the urethral opening, is a smooth triangular region delimited by the two ureteral orifices and the internal urethral orifice (Figure S4a); (ii) the bladder base, which faces backward and downward and lies adjacent to both the vagina and the supravaginal cervix (Figure S4b); (iii) the bladder dome, which lies superior to the base and is intra-abdominal (Figure S4c); and (iv) the extra-abdominal bladder (Figure S4d). Figure S5 and Videoclip S3 demonstrate the most frequent location of endometriotic bladder nodules, i.e. the bladder base. On two-dimensional (2D) ultrasound the appearance of DIE in the anterior compartment can be varied, including hypoechoic linear or spherical lesions, with or without regular contours involving the muscularis (most common) or (sub)mucosa of the bladder6, 38-43. The dimensions of the bladder nodule should be measured in three orthogonal planes. Bladder DIE is diagnosed only if the muscularis of the bladder wall is affected; lesions involving only the serosa represent superficial disease. Obliteration of the uterovesical region can be evaluated using the sliding sign, i.e. the transvaginal probe is placed in the anterior fornix and the uterus is balloted between the probe and one hand of the operator placed over the suprapubic region. If the posterior bladder slides freely over the anterior uterine wall, then the sliding sign is positive and the uterovesical region is classified as non-obliterated (Videoclip S4). If the bladder does not slide freely over the anterior uterine wall, then the sliding sign is negative and the uterovesical region is classified as obliterated44 (Figure S6). Adhesions in the anterior pelvic compartment are present in nearly one third of women with a previous Cesarean section and are not necessarily a sign of pelvic endometriosis44. The distal ureters should be examined routinely using the transvaginal probe. The ureters can be found by identifying the urethra in the sagittal plane and moving the probe towards the lateral pelvic wall. The intravesical segment of the ureter is identified and its course followed to where it leaves the bladder and then further, to the pelvic side wall and up to the level of the bifurcation of the common iliac vessels. It is helpful to wait for peristalsis to occur as this confirms ureteric patency. Ureters typically appear as long tubular hypoechoic structures, with a thick hyperechoic mantle, extending from the lateral aspect of the bladder base towards the common iliac vessels. Dilatation of the ureter due to endometriosis is caused by stricture (from either extrinsic compression or intrinsic infiltration) and the distance from the distal ureteric orifice to the stricture should be measured (Figure S7)35, 45, 46. Thorough evaluation of the ureter at the time of surgery is important in all cases in which ureteral involvement is suspected. In all women with DIE, a transabdominal scan of the kidney to search for ureteral stenosis is necessary, because the prevalence of endometriotic lesions in the urinary tract may be underestimated and women with DIE involving the ureter may be asymptomatic47-51. The degree of hydronephrosis should be assessed and graded using generally accepted ultrasound criteria52. Women with evidence of hydronephrosis should be referred for urgent stenting of a stenosed ureter to prevent further loss of renal function. According to Chapron et al.53, the most common sites of DIE in the posterior compartment are: USLs, posterior vaginal fornix, anterior rectum/anterior rectosigmoid junction and sigmoid colon. Sonographic assessment of the posterior compartment should aim at identifying the number, size and anatomical location of DIE nodules affecting these structures. On TVS, posterior compartment DIE lesions appear as hypoechoic thickening of the wall of the bowel or vagina, or as hypoechoic solid nodules which may vary in size and have smooth or irregular contours54. Some studies have defined the TVS diagnosis of DIE in the RVS as absence of the normal appearance of the hyperechoic layer between the vagina and rectum due to the presence of a DIE nodule55. Other researchers have used the terms ‘RVS DIE’ and ‘rectovaginal DIE (RV DIE)’ interchangeably to describe DIE in the RVS55, 56. The RVS is an individual anatomical structure with a specific location, whereas RV DIE describes DIE located in the rectovaginal area. The rectovaginal area includes the vagina, the rectum and the RVS. Furthermore, there is inconsistency in the definition of RV DIE in the literature. RV DIE has been described as endometriotic lesions which infiltrate both the rectum and the posterior vaginal fornix with possible extension into the RVS55. Others have used the term ‘rectovaginal endometriosis’ to describe nodules which primarily infiltrate the RVS with possible extension into the vagina and/or rectum. Isolated RVS endometriosis is uncommon. We propose that involvement of the RVS should be suspected when a DIE nodule is seen on TVS in the rectovaginal space below the line passing along the lower border of the posterior lip of the cervix (under the peritoneum)39 (Figure 4). Isolated RVS DIE is rare (Figure 5); RVS DIE is usually an extension of posterior vaginal wall (Figure 6), anterior rectal wall (Figure 7) or both posterior vaginal wall and anterior rectal wall involvement57 (Figure 8). The use of sonovaginography improves the detection of posterior vaginal and RVS DIE54, 58. The dimensions of the RVS DIE nodule should be recorded in three orthogonal planes and the distance between the lower margin of the lesion and the anal verge should be measured. This should be done whether the DIE is only in the vagina or only in the rectum, or involves the vagina, RVS and rectum. Low RVS lesions, when managed surgically, are associated with severe complications, including fistulae56, 59-61. We propose that involvement of the posterior vaginal fornix and/or lateral vaginal fornix should be suspected when a DIE nodule is seen on TVS in the rectovaginal space below the line passing along the caudal end of the peritoneum of the lower margin of the rectouterine peritoneal pouch (cul-de-sac of Douglas) and above the line passing along the lower border of the posterior lip of the cervix (under the peritoneum) (seen in Figure 4). Posterior vaginal fornix or forniceal endometriosis is suspected if the posterior vaginal fornix is thickened or if a discrete nodule is found in the hypoechoic layer of the vaginal wall (Figure S8a). The hypoechoic nodule may be homogeneous or inhomogeneous with or without large cystic areas (Figure S8a) and there may or may not be cystic areas surrounding the nodule6, 39, 41, 42. Figure S8b is an ultrasound image demonstrating posterior vaginal fornix DIE. The dimensions of the vaginal wall DIE nodule should be measured in three orthogonal planes. Hourglass-shaped or ‘diabolo’-like nodules occur when DIE lesions in the posterior vaginal fornix extend into the anterior rectal wall62 (Figure S9a). On ultrasound, the part of the DIE lesion situated in the anterior rectal wall is the same size as the part situated in the posterior vaginal fornix (Figure S9b). There is a small but easily visualized continuum between these two parts of the lesion. These lesions are located below the peritoneum of the POD and are usually large (3 cm on average)63. Normal USLs are usually not visible on ultrasound (Figure S10a). USL DIE lesions can be seen in the mid-sagittal view of the uterus (Figure S10b). However, these are best seen by placing the transvaginal probe in the posterior vaginal fornix in the midline in the sagittal plane and then sweeping the probe inferolaterally to the cervix. USLs are considered to be affected by DIE when a hypoechoic thickening with regular or irregular margins is seen within the peritoneal fat surrounding the USLs. The lesion may be isolated or may be part of a larger nodule extending into the vagina or into other surrounding structures. The thickness of a ‘thickened’ USL can be measured in the transverse plane at the insertion of the ligament on the cervix provided that the ligament can be distinguished clearly from adjacent structures (Figure S10c). In some cases the DIE lesion involving the USL is located at the torus uterinus (Figure S10d). If so, it is seen as a central thickening of the retrocervical area64. The dimensions of the USL DIE nodule should be recorded in three orthogonal planes. Bowel DIE classically involves the anterior rectum, rectosigmoid junction and/or sigmoid colon, all of which can be visualized using TVS. Figure S11a demonstrates a schematic drawing of a DIE lesion within the upper anterior rectum. Bowel DIE can take the form of an isolated lesion or can be multifocal (multiple lesions affecting the same segment) and/or multicentric (multiple lesions affecting several bowel segments, i.e. small bowel, large bowel, cecum, ileocecal junction and/or appendix)65. Although TVS can be used to visualize multifocal rectal DIE (Figure S11b), there are no published data assessing its performance. Computed tomographic colonography and magnetic resonance imaging (MRI) can be used to diagnose both multifocal and multicentric bowel endometriosis65. Histologically, bowel endometriosis is defined as the presence of endometrial glands and stroma in the bowel wall, reaching at least the muscularis propria66, where this invariably induces smooth-muscle hyperplasia and fibrosis. This results in thickening of the bowel wall and some narrowing of the bowel lumen. Normal rectal wall layers can be visualized on TVS: the anterior rectal serosa is seen as a thin hyperechoic line; the muscularis propria is hypoechoic, with the longitudinal smooth muscle (outer) and circular smooth muscle (inner) separated by a faint thin hyperechoic line; the submucosa is hyperechogenic; and the mucosa is hypoechoic37, 67 (Figure S12a). Bowel DIE usually appears on TVS as a thickening of the hypoechoic muscularis propria or as hypoechoic nodules, with or without hyperechoic foci (Figure S12b) with blurred margins. The morphological type of bowel lesion should be described according to Figure 9. Sonographically, bowel lesions are hypoechoic and in some cases a thinner section or a ‘tail’ is noted at one end, resembling a ‘comet’68 (Figure 9b). The normal appearance of the muscularis propria of the rectum or rectosigmoid is replaced by a nodule of abnormal tissue with possible retraction and adhesions, resulting in the so-called ‘Indian headdress’ or ‘moose antler’ sign (Figure 9c,e,f)42; the size of these lesions can vary. We propose that bowel DIE lesions noted on TVS be described according to the segment of the rectum or sigmoid colon in which they occur, with DIE lesions located below the level of the insertion of the USLs on the cervix being denoted as lower (retroperitoneal) anterior rectal DIE lesions, those above this level being denoted as upper (visible at laparoscopy) anterior rectal DIE lesions, those at the level of the uterine fundus being denoted as rectosigmoid junction DIE lesions and those above the level of the uterine fundus being denoted as anterior sigmoid DIE lesions (Figure 10). The dimensions of the rectal and/or rectosigmoid DIE nodules should be recorded in three orthogonal planes and the distance between the lower margin of the most caudal lesion and the anal verge should be measured using TVS. Because bowel DIE may affect the bowel simultaneously at different sites, other bowel lesions should be looked for carefully when there is a DIE lesion affecting the rectum (Figure S12b) or rectosigmoid. Preliminary data showed that rectal DIE lesions may be associated with a second intestinal lesion in 54.6% of cases34. Ultrasound diagnosis of POD obliteration31, 32 has been explained extensively earlier in this article. The obliteration can be graded as partial or complete depending on whether one side (left or right) or both sides, respectively, demonstrate a negative sliding sign. Furthermore, an experienced operator can identify the level of POD obliteration, i.e. specifying, in an anteverted uterus, whether it is at the retrocervical level (lower third of the uterus), mid-posterior uterus (middle third) and/or posterior uterine fundus (upper third)69 and, in a retroverted uterus, whether it is at the posterior uterine fundus, mid-anterior uterus and/or lower anterior uterine wall33(Figure S13). We propose that each endometrioma and DIE lesion should be measured systematically in three orthogonal planes, to obtain the length (mid-sagittal measurement), thickness (anteroposterior measurement) and transverse diameter (Figure 11). This approach of measuring in three planes applies to DIE lesions located in the bladder, RVS, vagina, USLs, anterior rectum and rectosigmoid. Additionally, in cases of endometriosis in the ureters, it is important to measure the distance between the distal ureteric orifice and a DIE lesion which causes a ureteric stricture; the stricture can be caused by either extrinsic compression or intrinsic infiltration. Once the stricture is identified along the longitudinal course of the ureter, one caliper should be placed at this level and the other at the distal ureteric orifice for measurement (Figure S7). In cases of multifocal bowel DIE lesions the total mid-sagittal length of the bowel segment involved, from caudal to cephalic aspect, should be measured (Figure 12). It is important to be aware that the retraction within rectosigmoid DIE lesions can result in an overestimation of the true thickness of the lesion and an underestimation of the true length of the lesion (Figure S14). This has been described as the ‘mushroom cap’ sign on MRI and can also be noted on TVS70. In cases of DIE lesions in the bowel or RVS, it is important to measure the distance between the anal verge and the lesion (Figure S15). It is possible to measure the distance from the anus to the bowel lesion using transrectal so