Anatomical distribution of endometriosis: A cross-sectional analysis of transvaginal ultrasound in symptomatic patients

Abstract

Purpose: The anatomical distribution of deep endometriosis (DE) is essential in treating patients with symptoms associated with the disease. There is an evidence gap in correlating clinical features and symptoms with disease patterns. The study aimed at determining DE anatomic distribution based on advanced transvaginal ultrasound and describe the relationship with symptoms obtained with the World Endometriosis Foundation Questionnaire.

Methods: A cross-sectional study included 549 ultrasound results and 370 questionnaire responses between July 2018 and January 2021. Descriptive statistics are presented. Continuous variables were compared by a simple t-test and ANOVA and categorical variables by the chi-squared test. Logistic regression and R² values summarised the relationship between positive ultrasound and possible predictor variables (software SAS version 9.4).

Results: The anatomical locations with signs of endometriosis on ultrasound were the right uterosacral ligament (USL) 23.3% (n = 128), left USL 21.3% (n = 117) and bowel 19.1% (n = 105). Endometriomas in the right and left ovaries (14%, n = 77, and 14.7%, n = 81 respectively), superficial endometriosis in 15.5% (n = 85), torus uterinus in 11.7% (n = 64), Pouch of Douglas (POD) in 9.7% (n = 53), rectovaginal septum in 4.2% (n = 23), vaginal fornix in 3.5% (n = 19). A negative 'sliding-sign' was noted in 25.3% (n = 139), and ovarian medial immobility was noted frequently (left 20.2%, n = 111 and right 16.9%, n = 93). Dyspareunia, dysmenorrhoea, infertility and family history were associated with endometriosis lesions (P < 0.05). Prediction models based on symptomatology presented low discriminatory power.

Discussion: This large real-life cohort associating the description of the anatomical distribution of endometriosis as seen on advanced TVS in symptomatic patients confirmed that uterosacral ligaments, torus uterinus, ovaries and bowel represent the most common anatomical sites of endometriosis. Also, the dynamic abnormalities elicited via ultrasound, such as the uterus 'sliding-sign' and ovarian mobility, remain common. The knowledge of the general locations of identifiable endometriosis on ultrasound and the dynamic abnormalities is essential to sonologists and sonographers in implementing advanced TVS protocols to detect endometriosis. In addition, the different presentations of dyspareunia can be associated with USL and bowel endometriosis. Subfertility might also be associated with USL, ovarian and bowel endometriosis. Nevertheless, prediction models showed suboptimal results.

Conclusions: Endometriosis is mainly distributed in USLs, bowel and ovaries. POD obliteration is frequent. Symptoms can be associated with anatomic locations; however, prediction models showed low clinical applicability.

Keywords: diagnosis; diagnostic imaging; endometriosis; symptoms; ultrasonography.

Figure 1

Schematic view of the anatomical distribution of endometriosis as seen on advanced ultrasound.

Figure 2

Endometriosis sonographic appearance. USL, uterosacral ligament; white arrow – endometriosis. (a) nodule on the uterosacral ligament, consisting of a hypoechoic nodular image in the topography of the hyperechoic ligament; (b) more subtle nodule, measuring 4 mm; (c) sonographic appearance of bowel endometriosis, in this case with the ‘sliding sign’ negative, where the anterior bowel wall does not move against the posterior aspect of the uterus (2c*); (d) hyperechoic projection on the surface of the Pouch of Douglas peritoneum depicting superficial endometriosis.

Figure 3

ROC curves for prediction models. (a) all variables: Amount of pelvic pain during last period; Tried to get pregnant for more than 6 months; Biological mother or sister diagnosed with endometriosis; Age of first period pain; Age when pelvic pain during intercourse or in the 24 hours following vaginal sexual intercourse/penetration started; Severity of pelvic pain at its worst during last period; Severity of pelvic pain at its worst ever; Severity of pelvic pain with vaginal intercourse/penetration at its worst ever; Longest amount of time trying to get pregnant. (b) 5 selected variables: Age of first period pain; Age when pelvic pain during intercourse or in the 24 hours following vaginal sexual intercourse/penetration started; Severity of pelvic pain with vaginal intercourse/penetration at its worst ever; Tried to get pregnant for more than 6 months; Biological mother or sister diagnosed with endometriosis.