Preoperative classification of endometriosis: a narrative review of revised American Society for Reproductive Medicine (r-ASRM), #Enzian, American Association of Gynecologic Laparoscopists (AAGL) 2021, and Numerical Multi-Scoring System of Endometriosis (NMS-E) systems

Background and Objective: Endometriosis affects approximately 10% of women of reproductive age globally and is a leading cause of chronic pelvic pain and infertility. Accurate classification is essential for preoperative diagnosis, surgical planning, and research. However, systems like the revised American Society for Reproductive Medicine (r-ASRM) rely on intraoperative findings and are not applicable preoperatively. This narrative review addresses this gap by examining three emerging classification systems-#Enzian, American Association of Gynecologic Laparoscopists (AAGL) 2021, and Numerical Multi-Scoring System of Endometriosis (NMS-E)-with a focus on their utility in pre-surgical assessment. Methods: We conducted a narrative literature review using PubMed, Embase, and Scopus covering the period from January 2015 to January 2025. A total of 66 articles related to the #Enzian classification and 19 articles on the AAGL 2021 classification were initially identified. Among them, 7 articles on #Enzian (3 original research articles and 4 reviews) and 5 articles on AAGL (2 original studies and 3 reviews) were selected based on their clinical relevance and methodological rigor. In addition, 5 original studies on the NMS-E system conducted at our institution were included. Further literature related to surgical planning, imaging techniques, and classification validation was also reviewed to support the comparative analysis. Key Content and Findings: The r-ASRM system remains widely used but lacks correlation with deep endometriosis and is not applicable preoperatively. The #Enzian system provides detailed anatomical mapping and is compatible with imaging but lacks scoring for pain and adhesions. It also does not offer a composite severity score or a specific evaluation of pouch of Douglas obliteration. Similarly, the AAGL 2021 classification introduces a surgical complexity score but does not assess pain or adhesions in detail and lacks specific evaluation of uterosacral ligament involvement. The NMS-E system uniquely integrates pelvic examination and ultrasound findings into an E-score reflecting lesion, pain, and adhesion severity. Validation studies demonstrate a strong correlation with surgical duration (r=0.724, P<0.01). Patients with lower NMS-E adhesion scores had better postoperative fertility outcomes (P<0.05). While #Enzian and AAGL 2021 are gaining international adoption, NMS-E remains in the early stages of clinical uptake. Conclusions: Each system contributes to improved preoperative assessment but has limitations. NMS-E adds value by incorporating symptoms and adhesion scoring. No system is yet ideal; further integration and validation across diverse clinical settings are needed. This review provides comparative insights to support classification system refinement and practical application.