Value of transvaginal sonography in assessing severe pelvic endometriosis

Abstract

Pelvic endometriosis is defined as the presence of ectopic endometrial tissue outside the uterus. There are three types: endometrial cysts, superficial peritoneal lesions and lesions of deep endometriotic location1. It can be associated with the presence of adhesions and anatomy modifications such as partial or complete obliteration of the pouch of Douglas. In addition, it is commonly responsible for pelvic pain and infertility, but there is no clear relation between either location or extent of endometriosis and symptoms. Indeed, whilst patients with extensive disease may be asymptomatic, some women with minimal, superficial endometriosis limited to peritoneal surfaces describe severe dysmenorrhea and chronic pelvic pain, raising concerns regarding the pathophysiology of pain associated with endometriosis. Laparoscopy with biopsy permits the evaluation of severity and quantification of lesions within the pelvic cavity and this technique is considered the gold standard for diagnosing pelvic endometriosis. Several systems have been advocated to score pelvic endometriosis, the most commonly used being the revised classification system of the American Society of Reproductive Medicine (‘ASRM classification’)2. This system evaluates the presence, size and number of endometriotic deposits and cysts, the presence and severity of any adhesions, and the degree of obliteration of the pouch of Douglas. However, in accordance with Redwine3, we do not think that it can gauge accurately all pelvic endometriotic lesions: although the ASRM classification is able to evaluate superficial and ovarian endometriosis as well as associated adhesions, deep endometriotic locations are not taken into account, especially those affecting the intestine. This is particularly important as recent studies have underlined the high incidence of these lesions and their negative impact on symptoms, quality of life4 and fertility5. There is no clear consensus regarding the definition of severe endometriosis. From a clinical point of view, the type of symptoms (e.g. pelvic pain, dysmenorrhea, dyspareunia) and the degree of infertility cannot be used to evaluate the severity of lesions; to achieve this one needs objective criteria. Surgery has been suggested as the most reproducible option, but Vercellini et al.6 demonstrated the absence of correlation between ASRM stage and fertility or recurrence outcomes. Recently, Chapron et al.7 proposed a surgical classification for deep infiltrating endometriosis (DIE) according to one of the following four locations (in order of decreasing frequency): uterosacral ligament (USL), intestine, vagina and bladder. When there are multiple sites of DIE, the patients are classified according to the worst of these locations7. However, no one has investigated the prognostic value of the evolution of symptoms after surgery, quality of life, fertility or recurrence with respect to this new classification. Numerous studies have demonstrated the usefulness of transvaginal sonography (TVS) as a first-line technique for the diagnosis of pelvic endometriosis, thanks to its widespread availability and cost effectiveness8-10. In this issue of the Journal, Holland et al.10 use the ASRM classification as the primary gold standard with which to validate their ultrasound findings. TVS examinations were performed blindly by four ultrasound operators with a high level of expertise in gynecological ultrasonography, but there was considerable discrepancy in the number of TVS examinations performed by each operator (Examiner A performed 104 (51.7%), Examiner B 68 (33.8%), Examiner C 18 (9%) and Examiner D only 11 (5.5%) examinations). Moreover, in the statistical analysis, data from Examiners C and D were not taken into account, representing, we believe, a potential bias. Hence, the conclusion of this study should be interpreted with caution. The learning curve of TVS for the diagnosis of pelvic endometriosis has rarely been specifically assessed. In our experience, there is high interobserver variability in the learning curve11, underlining the need to clarify the term ‘operators with a high level of expertise’. Few data are available on the value of TVS for the diagnosis of adhesions associated with endometriosis or other disorders. Recently, Guerriero et al.12 suggested that TVS was able to detect or exclude the presence of adhesions in women with an ultrasonographic suspicion of endometrioma. Holland et al.10 also evaluated pelvic adhesions. In accordance with Okaro et al.13, they assessed ovarian mobility by a combination of gentle pressure with the vaginal probe and abdominal pressure by the examiner's free hand, as in bimanual examination. Holland et al.10 used a classification of adhesions analogous to that used in the ASRM classification, namely, minimal, moderate, or severe adhesions. In addition, the presence of adhesions in the pouch of Douglas was assessed. The uterus was ‘gently mobilized by a combination of pressure on the cervix with the ultrasound probe alternating with pressure on the fundus from the examiner's free hand on the abdominal wall’. This allowed diagnosis of complete or partial obliteration of the pouch of Douglas. These criteria seem very subtle and external validation with assessment of interobserver variability would be needed before recommending its use routinely. As pointed out by Holland et al.10, the success of surgery for pelvic endometriosis is highly dependent on the expertise and training of the operating surgeon. In this setting, preoperative mapping of the different locations of pelvic endometriosis is required to allow optimal preoperative surgical planning and to allow the patients to give informed consent. Moreover, the detection of extensive lesions on ultrasound allows referral of the patient to a regional tertiary center. While general gynecological surgeons are often able to perform excision of endometrial cysts and peritoneal implants, a great deal of skill and experience is required for the treatment of lesions in deep endometriotic locations. As with oncological surgery, this reinforces the concept that patients with extensive disease on TVS who are not correctly evaluated by the revised ASRM classification should be referred to a tertiary referral center where complete treatment can be carried out. In conclusion, there is no consensus regarding the classification of the severity of pelvic endometriosis. A combination of the revised ASRM and anatomical classification is probably required to achieve a complete evaluation of endometriotic lesions. In this setting, TVS is the first-line examination allowing initial triage of women suffering from endometriosis.