Uterine involvement by endometriosis: Sonographic features from elusive findings to apparent adenomyosis

The primary aim of this study is to investigate whether there are any minor sonographic uterine findings, not typical for adenomyosis, in endometriosis patients. The secondary objective is to determine the prevalence of sonographic features of adenomyosis in an infertile population with endometriosis.

The investigation was of 291 infertile women with endometriosis, either manifesting endometrioma (OMA) or diagnosed through laparoscopy, who were investigated for two-dimensional transvaginal sonographic (2D-TVS) features of adenomyosis. These patients were grouped as either having endometriosis with adenomyosis (EwA,n = 121) or without adenomyosis (EwoA, n = 170). Additionally, patients without both endometriosis and 2D-TVS features of adenomyosis constituted the control group (n = 170).

At least one 2D-TVS feature of adenomyosis was detected in 41.6 % (n = 121) of women with endometriosis. Asymmetrical myometrial thickening of uterine walls (57.9 %), hyperechogenic islands (47.1 %), and fan-shaped shadowing (46.9 %) were relatively more prevalent 2D-TVS findings among EwA patients. Multiple OMA (p = 0.038), OMA ≥ 4 cm (p = 0.034), and total OMA volumes were found to be higher (p = 0.004) in the EwA group. Additionally, uterine volumes were found to be 96.7 cm³, 73.0 cm³, and 64.2 cm³ in the EwA, EwoA, and control groups, respectively (EwA vs EwoA, p < 0.001; EwoA vs control, p <0.001). Multivariate linear regression analysis revealed that the presence of endometriosis was independently associated with an increase in uterine volume (β = 0.243, p < 0.001).

A stepwise and statistically significant volume increase from the control group to the EwoA and then to the EwA group may reflect a spectrum of uterine involvement in endometriosis. This might indicate that many uterine endometriosis cases are still hidden from view, possibly demonstrating an "iceberg phenomenon".