Anatomical distribution of ovarian and deep endometriosis using a multimodal diagnostic approach applying the updated international definition: A prospective observational study

OBJECTIVE: To (1) determine how application of the updated international definition of deep endometriosis (DE) alters apparent disease prevalence across pelvic sites, and (2) characterize the distribution of endometriosis phenotypes, including ovarian (OE), DE, and superficial (SE) disease, using a standardized multimodal approach integrating transvaginal ultrasound (TVS), surgical, and histopathologic findings. STUDY DESIGN: Prospective observational study conducted at a tertiary endometriosis center between November 2021 and January 2023. METHODS: Consecutive patients undergoing laparoscopy for chronic pelvic pain or infertility underwent systematic TVS and intraoperative assessment performed by a single fellowship-trained operator. Lesions were classified as DE if confirmed by at least two of three modalities. Prevalence estimates under the updated definition were compared descriptively with those using the previous > 5 mm criterion. RESULTS: Among 131 participants, OE were present in 45.4 % (59/130; excluding one participant with prior bilateral oophorectomy) and DE in 64.1 % (84/131). Among individuals with DE, the uterosacral ligaments were the most frequently involved site (52.7 %), followed by bowel (18.3 %), pararectal spaces (16.8 %), posterior vaginal fornix (12.2 %), and parametrium (6.1 %). Under the updated definition, DE prevalence increased from 22.9 % to 52.7 % at the uterosacral ligaments and from 10.7 % to 16.8 % at the pararectal spaces compared with the prior > 5 mm threshold. Isolated SE was found in 32.8 % (43/131) of participants, while OE and DE coexisted in over 90 % of cases with endometrioma. CONCLUSIONS: The application of the updated DE definition substantially increases the reported prevalence across key posterior pelvic sites by reclassifying lesions previously categorized as superficial. Comprehensive multimodal assessment further delineates the distribution and overlaps of endometriosis phenotypes, providing a reproducible framework for future multicenter and outcome-based validation.