Integrating the concept of advanced gynaecological imaging for endometriosis

It is now more than four decades since sonography was first used to evaluate the obstetric patient.1 At its beginning, the questions asked were basic. For example, is there a live pregnancy? Is there a singleton or a twin gestation? Where is the placenta located? At the time, it was not immediately envisioned that sonography would be a very useful diagnostic modality that could answer questions related to the presence of subtle anatomical defects such as cleft lip and palate, suggest the presence of chromosomal abnormalities or contribute to the clinical management of the growth-restricted fetus.1 Now days it is not unusual for women to have one or even several ultrasound examinations during a pregnancy.2 Clear pathways for escalating the management of fetal anomalies identified at community-based imaging centres have become embedded in quality assurance programs. Maternal-fetal medicine centres of excellence for advanced obstetric imaging as well as surgical and medical management of amenable fetal anomalies have become established.3-5 Indeed, the recent technological advances in ultrasound imaging, the use of high-frequency ultrasound probes with 3D capabilities and its utilisation for chromosomal and growth restriction screening in early pregnancy continue to magnify our interest in the use of sonographic imaging for the obstetric patient.1 For the gynaecological patient, the evolution of gynaecological imaging is demonstrating a similar trajectory. In the last two decades, gynaecological imaging has moved beyond routine measurements of the uterus and adnexae and the description of adnexal masses as simple or complex.6, 7 It now has a role in the triage of adnexal lesions,8, 9 the quantification of female pelvic organ prolapse,10 the preoperative assessment of the pelvis in women planning surgery for endometriosis11-13 and procedural gynaecological imaging such as saline/contrast sonohysterosalpingogram.14, 15 This evolution of gynaecological imaging is not only a consequence of the technological advances in ultrasound imaging but also related to the emergence of women's health specialists with special interest and training in gynaecological imaging.16 With the evolution of gynaecological imaging and the emergence of specialists with experience and training in this speciality, it is now imperative to establish and integrate clear referral pathways for escalating sonographic anomalies identified in a gynaecological patient similar to that currently in place for the obstetric patient. Such a hierarchical approach to evaluating gynaecological anomalies was demonstrated by the International Ovarian Tumor Analysis (IOTA) group when they externally validated a two-step strategy for assessing adnexal lesions where the simple rules for characterising adnexal masses yielded an inconclusive result with less experienced operators.7 This two-step strategy reached a sensitivity of 90% and a specificity of 93% for detecting ovarian malignancy and is now included in the RCOG guidelines for evaluating ovarian pathology in premenopausal women.7, 17 The principles underpinning this two-step approach described by the IOTA group is also feasible for the sonographic assessment of the pelvis in women with suspected endometriosis. For example, an endometrioma is a common phenotype of endometriosis. Chara-cteristically, endometriomas appear as unilocular or multilocular (up to 4 locules) adnexal cysts with ground glass echogenicity of the cyst fluid and no solid papillations18 They are easily classifiable using pattern recognition and/or the simple rules approach.19, 20 They are also soft markers for higher stage endometriosis21 and often occur in association with other phenotypes of endometriosis.22, 23 Indeed, evidence demonstrates that more than 50% of endometriomas are associated with other phenotypes of endometriosis.23 The presence of endometriomas in women presenting with pelvic pain therefore could only be a ‘tip of the ice berg’ in the disease spectrum of endometriosis and should mandate a careful search for other phenotypes of endometriosis (bowel and uterosacral deep endometriosis) and their markers of local invasiveness (ovarian adhesions and POD obliteration) using transvaginal ultrasound (TVS)23 This is important because for symptomatic women with endometriomas, preoperative characterisation of disease severity is critical to appropriate surgical management especially as maximal cytoreduction at the first surgical intervention delivers the greatest benefit.24, 25 With the evolution of transvaginal sonography as the first-line imaging modality for evaluating the pelvis in women with suspected endometriosis,11, 12 its utilisation must employ systematic, objective and reproducible TVS techniques that will facilitate comparisons between and within units involved with endometriosis ultrasound.26 However, proficiencies in these new TVS techniques for evaluating the pelvis in women with suspected endometriosis require additional training and expertise beyond that available for performing routine gynaecological imaging.6 This is especially important as emerging evidence now demonstrates different learning curve parameters for these various phenotypes of endometriosis.27 More recently, Menakaya et al. described a five-domain TVS-based approach to the evaluation of the pelvis in women with suspected endometriosis.28 This structured approach provides the basis for evidence-based reproducible assessment of the pelvis in women with suspected endometriosis with the ability to improve ‘pattern recognition’ of the more severe forms of endometriosis. The five-domain approach builds on the techniques employed for a routine gynaecological ultrasound, but raises the benchmark required for reporting both ovarian and extra-ovarian endometriosis (Table 1). In addition, it can facilitate an objective stratification of competency in the expertise required for performing advanced gynaecological imaging in women with suspected endometriosis.28 Thick-walled ovarian cysts with homogenous low-level internal echos ’Ground glass appearance’ Assessing for nonbowel deep infiltrating endometriosis (DIE) Anterior, lateral and posterior pelvic compartment Nodules – solid hypo-echoic rounded-shape lesions Linear thickenings – hypo-echoic linear thickening Plaques – hypo-echoic lesions with irregular shape. Noncompressible hypo-echoic lesion on muscularis propria (May infiltrate the mucosa layer) The five-domain TVS-based approach therefore improves the quality of information demanded and derived from an ultrasound evaluation of the pelvis in a woman with suspected endometriosis prior to surgery. It has clearly defined endpoints and includes sonographic techniques for demonstrating specific phenotypes of endometriosis that can be verified with gold standard laparoscopy.28 Thus, this approach could be utilised as an advanced sonographic protocol for evaluating the pelvis for women in whom an endometrioma has been identified with traditional gynaecological imaging. Indeed, an advanced sonographic evaluation of the pelvis for endometriosis using the five-domain TVS approach and performed by an appropriately trained sonologist should not only report the presence of phenotypes of endometriosis but also describe the relationships between them28 (Fig. 1). This proposed approach to the evaluation of the pelvis in women with endometrioma is consistent with the principle of a two-step strategy for evaluating gynaecological anomalies using ultrasound. Integrating the concept of advanced gynaecological imaging in the assessment of women with endometrioma is also consistent with the current paradigm for a cost-effective approach to the management of women with endometriosis.29 Indeed, there are significant clinical and healthcare cost implications with this approach. For the healthcare system, it represents a cost-effective, non-invasive diagnostic adjunct to the surgical management of women planning laparoscopy for endometriosis. It also has the potential to triage women with no demonstrable hard markers of endometriosis on TVS to medical and/or complimentary options of care currently available for chronic pelvic pain in order to reduce the healthcare costs associated with negative laparoscopies.28, 30, 31 For the primary physician, understanding the degree of endometriosis severity will limit the current random allocation of women with higher stage endometriosis to either a generalist or advanced endoscopic surgeon and facilitate appropriate referral to tertiary laparoscopic centres of expertise for women with higher stage endometriosis in accordance with the recent World Endometriosis Society (WES) consensus statement.28, 29, 31 Most importantly, it will empower the woman by improving her comprehension of the severity of endometriosis, engender her ability to be actively involved in decision-making regarding who and where to obtain appropriate surgical treatment and potentially reduce her exposure to multiple laparoscopies.28, 30, 31