What is the Enzian classification for staging deep infiltrating endometriosis?

Enzian Classification of Endometriosis

Overview and Purpose

The Enzian classification is a specialized staging system designed specifically to describe deep infiltrating endometriosis (DIE) and should be used in conjunction with the r-ASRM classification whenever deep disease is present to provide complete operative documentation. 1

The system divides the pelvis into anatomical compartments and grades the severity of deep endometriotic lesions, addressing a critical gap in the widely-used r-ASRM classification, which inadequately describes deep disease. 1

Anatomical Compartments

The #Enzian classification organizes deep endometriosis into the following compartments: 2

Primary Deep Endometriosis Compartments:

• Compartment A (Vertical): Rectovaginal septum and vagina 3, 2
• Compartment B (Horizontal): Uterosacral ligaments, cardinal ligaments, parametrium, and pelvic sidewalls 3, 2
• Compartment C (Dorsal): Rectum and sigmoid colon 3, 2

Additional Locations (F-Compartments):

• FA: Adenomyosis 4, 2
• FB: Urinary bladder involvement 4, 2
• FU: Ureteric involvement with signs of obstruction 4, 2
• FI: Other intestinal locations (appendix, small intestine) 4, 2
• FO: Other extragenital locations 4, 2

Ovarian and Tubal Disease:

• O: Ovarian endometriosis 4, 2
• T: Tubo-ovarian adhesions 4, 2
• P: Peritoneal disease 3

Severity Grading

For compartments O, T, A, B, and C, the #Enzian classification assigns severity grades 1-3 based on lesion size or adhesion severity: 4

• Grade 1: Mild disease (lesions <1 cm) 5
• Grade 2: Moderate disease (lesions 1-3 cm) 5
• Grade 3: Severe disease (lesions >3 cm) 5

The grading system allows for precise documentation of disease extent, with studies showing that 45% of deep infiltrating lesions are Grade 1,26% Grade 2,19% Grade 3, and 10% Grade 4 in surgical populations. 6

Clinical Application

Preoperative Use:

Enzian classification can be applied preoperatively using transvaginal ultrasound (TVS) supplemented by transabdominal sonography (TAS) or MRI to predict surgical extent and plan operative time. 1, 4

• TVS/TAS demonstrates sensitivity ranging from 50% (FI compartment) to 95% (A compartment) for detecting endometriotic lesions 4
• Specificity ranges from 86% (T compartment) to 100% (FB, FU, FO compartments) 4
• Concordance between preoperative ultrasound and surgical findings ranges from 86-99% for presence/absence of lesions 4
• Concordance for severity grading ranges from 71-92% across compartments 4

Surgical Documentation:

The classification provides standardized terminology for operative reports, enabling consistent communication between surgeons and facilitating research comparisons. 2

Relationship to r-ASRM Classification

A critical finding is that deep infiltrating endometriosis occurs across all r-ASRM stages, including minimal disease (Stage I), demonstrating why Enzian supplementation is essential: 3

• Among women with r-ASRM Stage I (minimal disease), 65% had DIE in compartment B, 45% in compartment A, and 26% in compartment C 3
• The number of affected Enzian compartments progressively increases from r-ASRM Stages 1-4, with maximum involvement of six compartments in Stage 4 patients 3
• Using r-ASRM alone leads to systematic underestimation of disease severity when deep endometriosis is present 3

Clinical Limitations

Despite its anatomical precision, the Enzian classification has poor correlation with symptom severity, quality of life, and infertility outcomes, and limited prognostic value for treatment response. 1

• The system does not predict pain severity or fertility outcomes 1
• Predictive capacity for treatment response remains uncertain 1
• External validation studies are still needed 1

Common Pitfalls:

• Do not assume higher Enzian grades correlate with worse pain—the classification describes anatomical extent, not symptom burden 1
• Do not use Enzian alone—it must be combined with r-ASRM to capture peritoneal and ovarian disease comprehensively 1, 2
• Avoid over-diagnosing deep disease—lesions must extend >5 mm beneath the peritoneal surface or involve specific organs (bowel, bladder, ureter, vagina) to qualify as DIE 1, 7

Distribution Patterns

In surgical populations with deep infiltrating endometriosis, lesion distribution follows this pattern: 6

• Compartment B (uterosacral/parametrial): 41% 6
• Compartment A (rectovaginal): 26% 6
• Compartment C (rectal): 24% 6
• Adenomyosis (FA): 4% 6
• Bladder (FB): 2% 6
• Bowel (FI): 2% 6
• Ureter (FU): 1% 6

The most commonly affected compartment in clinical series is C2 (rectum/sigmoid with 1-3 cm lesions), particularly in nulliparous women presenting with pelvic pain. 5

Practical Implementation

When documenting endometriosis surgically, use the following approach: 1, 2

1. Apply r-ASRM classification for peritoneal implants, ovarian endometriomas, and adhesions
2. Add Enzian classification for any deep infiltrating disease
3. Document each affected compartment with its severity grade
4. Record F-compartments for extragenital involvement
5. Include this dual classification in the operative report

This "classification toolbox" approach ensures comprehensive disease mapping while maintaining compatibility with historical literature and research databases. 1, 8