Transvaginal Strain Elastography Methodology in Deep Endometriosis: Narrative Review and Proposal of a Standardized Imaging Protocol

OBJECTIVES: Transvaginal strain elastography (SE) has emerged as a complementary technique to transvaginal ultrasound for deep endometriosis (DE) evaluation by exploiting tissue stiffness between lesions and surrounding structures. However, its clinical adoption remains limited by marked methodological heterogeneity across studies. The objective of the study is to critically review published transvaginal SE methodologies in DE and propose a standardized, anatomically grounded imaging protocol illustrated by a prospective observational cohort. METHODS: This methodological study evaluated a proposed standardized transvaginal SE protocol for DE through a 2-phase framework. First, a narrative review analyzed literature heterogeneity in acquisition techniques, compression, region-of-interest (ROI) placement, reference tissue selection, output parameters, and reproducibility. Second, a prospective observational cohort of women with suspected or confirmed DE was conducted to assess the feasibility, practical applicability, and consistency of the proposed protocol under real clinical conditions, without assessment of diagnostic accuracy. RESULTS: The review identified substantial heterogeneity among studies regarding compression control, ROI geometry and depth matching, reference tissue, and reproducibility. Using the proposed standardized protocol, stable and interpretable elastograms were consistently obtained across typical anatomical sites of DE (uterosacral ligaments, rectovaginal septum, and anterior rectosigmoid). Under controlled acquisition, lesions consistently exhibited increased stiffness relative to adjacent non-endometriotic tissue, while internal heterogeneity and apparent lesion extent varied by location. Common technical pitfalls were successfully mitigated through standardized acquisition strategies. CONCLUSION: Transvaginal SE is a feasible and informative adjunct in DE imaging but is limited by methodological variability. The proposed standardized protocol improves reproducibility by facilitating consistent clinical application and future research.