World Endometriosis Society Consensus Guidelines on Classification
The World Endometriosis Society (WES) 2017 consensus recommends using a "classification toolbox" approach: all women undergoing surgery for endometriosis should have the revised American Society for Reproductive Medicine (r-ASRM) classification completed, women with deep endometriosis should additionally have the Enzian classification completed, and women concerned about future fertility should additionally have the Endometriosis Fertility Index (EFI) completed and documented in medical records. 1
Core Classification Framework
The WES consensus produced 28 statements through a rigorous international process involving 55 representatives from 29 organizations across 19 countries, including both medical professionals and patient advocacy groups 1. The primary goal is to bridge diagnosis with optimal treatment by providing prognostic information about fertility impact, pain symptoms, quality of life, treatment response, and recurrence risk 1.
The Classification Toolbox Components
For ALL surgical cases:
- r-ASRM classification must be completed and staged (Stages I-IV based on anatomic distribution and severity) 1
Additional classifications based on presentation:
- Enzian classification - Add this for any woman with deep infiltrating endometriosis to map compartments A (rectovaginal), B (uterosacral/cardinal ligaments), and C (rectum) 1
- Endometriosis Fertility Index (EFI) - Add this for any woman with future fertility concerns to predict pregnancy rates 1
Rationale and Context
The consensus acknowledges that existing classification systems have significant limitations—they correlate poorly with symptom severity and have limited predictive value for treatment outcomes 1. Despite these shortcomings, the WES strongly recommends systematic classification because it increases familiarity among surgeons and multidisciplinary teams, provides a common language for disease understanding, and benefits women through improved counseling and treatment planning 1.
Key Principles
The consensus prioritized making strong recommendations when:
- Classification systems provide value to women with moderate-to-strong evidence
- Simple, low-cost, minimally invasive classifications could reduce suffering burden even with weak evidence
- Risk or expense of classification justified non-use when evidence was marginal 1
Important caveat: None of the 28 consensus statements achieved unanimous agreement without caveats, and 2 statements failed to achieve majority consensus 1. This reflects the genuine controversy and limitations in current classification approaches.
Implementation Considerations
The consensus emphasizes that surgery represents a "pivotal moment" for classification since it provides direct visualization of disease 1. The main implementation barrier is whether surgeons will dedicate time to complete these forms, but the consensus argues this is a fundamental duty to women undergoing invasive procedures 1.
For research purposes and non-surgical cases, the WES recommends using the World Endometriosis Research Foundation (WERF) Endometriosis Phenome and Biobanking Harmonisation Project data collection tools 1.
Clinical Application Algorithm
At time of diagnostic/therapeutic laparoscopy:
- Complete r-ASRM staging for all cases
- Assess for deep infiltrating disease → if present, add Enzian
- Discuss fertility plans → if future pregnancy desired, add EFI
- Document all classifications in operative and medical records
Use classifications to inform:
- Prognosis counseling (pain, fertility, recurrence risk)
- Treatment selection (medical vs. surgical vs. combined)
- Follow-up planning and monitoring strategies
This represents the current best practice until superior classification systems with better validation emerge 1. The consensus acknowledges these tools are imperfect but necessary for standardizing care and advancing the field through comparable data collection.