Clinical overview
Staging systems for endometriosis exist because the disease is heterogeneous: from a tiny peritoneal implant in an asymptomatic woman to a frozen pelvis with bowel and bladder involvement. A single name — "endometriosis" — does too much work. Staging exists to: (1) communicate disease burden between clinicians; (2) guide surgical planning; (3) provide a research substrate; and (4) predict fertility outcome (though imperfectly).
The registrar must know the rASRM (revised American Society for Reproductive Medicine) system in detail because it is used in nearly every operation note and theatre summary in South Africa. You should also know the newer ENZIAN classification (for deep infiltrating endometriosis) and the EFI (Endometriosis Fertility Index) because they capture what rASRM misses: bowel/bladder depth, ureteric involvement, and the fertility prognosis.
Adenomyosis lacks a universally accepted staging system. The MUSA (Morphological Uterus Sonographic Assessment) features and the more recent grading systems based on depth of myometrial involvement (focal vs diffuse, anterior vs posterior wall, percentage of myometrium involved) are the current pragmatic tools.
The chapter explains each system, what it measures and what it doesn't, and how to apply them in the South African public-sector context where MRI access is uneven and most staging happens at laparoscopy or by skilled ultrasound.
Core knowledge
rASRM staging of endometriosis (1996)
rASRM stage rises with endometrioma burden, adhesions and pouch of Douglas obliteration, not pain severity.
A point-based system applied at laparoscopy. Points are awarded for:
- Peritoneal implants — number, size, depth (superficial vs deep).
- Ovarian endometriomas — size, side.
- Adhesions — film vs dense, surface area of involvement.
- Pouch of Douglas obliteration — partial or complete.
Total points produce a stage:
- Stage I (minimal): 1–5 points. Few superficial implants; no significant adhesions; no endometriomas.
- Stage II (mild): 6–15 points. More implants; some superficial peritoneal disease; minor adhesions.
- Stage III (moderate): 16–40 points. Endometrioma(s) >1 cm, multiple deeper implants, significant adhesions.
- Stage IV (severe): >40 points. Large endometriomas (often bilateral), dense adhesions, often partial or complete obliteration of pouch of Douglas, bowel or bladder involvement.
rASRM strengths: widely used, simple, allows comparison between surgeons. rASRM weaknesses: poor correlation with pain (a small implant on a sacral nerve can be devastating; large lesions can be silent); poor correlation with fertility outcome; does not account for deep infiltrating disease beyond simple "deep" designation; does not capture extrapelvic disease.
ENZIAN classification (revised 2021, #ENZIAN)
ENZIAN maps deep disease by pelvic compartment so bowel, bladder and ureter involvement are not missed.
Designed specifically for deep infiltrating endometriosis (DIE). Now the recommended companion to rASRM. Captures location and depth in three anatomical compartments and additional involvement:
- Compartment A (rectovaginal): vagina, rectovaginal septum.
- A1: <1 cm
- A2: 1–3 cm
- A3: >3 cm
- Compartment B (lateral): uterosacral ligaments + parametrium.
- B1–B3 (sided: left/right), graded by depth.
- Compartment C (rectum/sigmoid):
- C1: <1 cm
- C2: 1–3 cm
- C3: >3 cm
- F (additional involvement):
- FA: adenomyosis
- FB: bladder
- FU: ureter (intrinsic vs extrinsic)
- FI: bowel beyond rectum
- FO: other (diaphragm, abdominal wall, nerve)
Used for surgical planning — particularly for multidisciplinary cases involving colorectal, urology, and gynaecology.
Endometriosis Fertility Index (EFI)
Adamson and Pasta, 2010. A 0–10 score combining:
- Surgical findings at the time of laparoscopy (functional status of tubes, fimbriae, ovaries).
- Historical factors (age, duration of infertility, prior pregnancy).
- Total rASRM score and the rASRM endometriosis score.
EFI strongly predicts natural conception rates in the months after surgery and is more useful than rASRM stage alone for counselling women trying to conceive.
Other endometriosis classification systems
- AFS (American Fertility Society) 1985 — the original system, superseded by rASRM.
- WERF EPHect (World Endometriosis Research Foundation) — a research-grade phenotype framework, not used clinically.
Adenomyosis classification
Adenomyosis description combines focal versus diffuse pattern, MUSA features and depth of myometrial involvement.
There is no single universally accepted system. The pragmatic ones:
MUSA (Morphological Uterus Sonographic Assessment) criteria — sonographic features:
- Asymmetric myometrial thickening
- Myometrial cysts
- Hyperechoic islands
- Fan-shaped shadowing
- Translesional vascularity
- Irregular junctional zone
- Interrupted junctional zone
Diagnosis = ≥2 features on transvaginal ultrasound. Has revolutionised non-invasive diagnosis.
Focal vs diffuse:
- Focal adenomyosis (adenomyoma) — discrete nodule; behaves like a fibroid clinically.
- Diffuse adenomyosis — generalised involvement; bulky boggy uterus.
Depth of myometrial involvement (on MRI):
- Superficial (<25%)
- Intermediate (25–50%)
- Deep (>50%)
Symptomatic grading:
- Mild (annoying but not life-affecting), moderate (impacting function), severe (debilitating + significant haemorrhage).
Assessment
When to stage
- At every laparoscopy for endometriosis — document rASRM + ENZIAN at minimum.
- At pre-operative MRI — to plan multidisciplinary surgery for DIE.
- At ultrasound for adenomyosis — use MUSA criteria.
- Pre-IVF — calculate EFI if recent laparoscopy data available.
How to stage at laparoscopy
A systematic survey of all peritoneal surfaces:
- Anterior pelvic peritoneum (bladder, anterior cul-de-sac).
- Vesicouterine fold.
- Right pelvic side wall (ovary, fallopian tube, uterosacral, ureter).
- Pouch of Douglas (including assessment of obliteration — partial vs complete).
- Left pelvic side wall.
- Posterior uterus.
- Bowel surfaces (rectum, sigmoid, ileum, appendix).
- Diaphragm and upper abdomen.
Record number, size, depth (superficial < 5 mm; deep ≥ 5 mm), and colour (red active, blue/brown chronic, white burnt out). Photograph each compartment.
Take biopsies of representative lesions — histology confirms (endometrial glands + stroma) and excludes mimics.
Ultrasound staging of adenomyosis
Apply MUSA criteria systematically:
- Document features present.
- Locate (anterior vs posterior wall).
- Estimate percentage involvement.
- Measure junctional zone thickness (>12 mm suggestive).
Management
Staging guides management but does not dictate it — symptom severity, fertility goals, and patient preference dominate.
Endometriosis staging → management influence
- Stage I/II: Often managed medically first (combined hormonal contraception, progestogens). Surgery for ovarian endometrioma >4 cm, or where pain inadequately controlled. See endometriosis-pathophysiology for full medical management.
- Stage III/IV: Multidisciplinary planning. MRI for ENZIAN classification. Consider referral to a specialist endometriosis centre.
- EFI ≥7: Reasonable expectant management or surgery; good natural conception prospects.
- EFI ≤4: Direct referral for IVF after surgical treatment of pain-causing lesions.
Adenomyosis staging → management
- Mild/focal disease + completed family: progestogen-only options (Mirena, dienogest).
- Mild/focal + wanting fertility: medical management + assisted reproduction.
- Severe diffuse disease + completed family: hysterectomy (definitive).
- Severe diffuse + wanting fertility: very difficult; GnRH analogues, controlled stimulation IVF, uterine-sparing surgery in selected cases (high recurrence).
Red flags / pitfalls
- Pain disproportionate to stage — common; treat symptoms not the stage.
- Trying to "improve" rASRM score by ablating — incomplete; excision is gold standard for deep disease.
- Missing extrapelvic disease at staging — survey diaphragm in all cases.
- Calling adenomyosis a fibroid on ultrasound — MUSA criteria help distinguish.
- Acting on stage alone without symptom context — Stage IV asymptomatic disease in a perimenopausal woman may not need surgery.
- Forgetting EFI in fertility counselling — staging without EFI is inadequate for the woman trying to conceive.
- Not documenting ENZIAN when DIE is present — surgical planning depends on it.
Evidence anchors
- ASRM. Revised American Society for Reproductive Medicine classification of endometriosis: 1996. Fertil Steril 1997.
- Keckstein J, et al. The #ENZIAN classification: a comprehensive non-invasive and surgical description system for endometriosis. Acta Obstet Gynecol Scand 2021.
- Adamson GD, Pasta DJ. Endometriosis fertility index: the new, validated endometriosis staging system. Fertil Steril 2010.
- ESHRE Guideline: Endometriosis (2022).
- Van den Bosch T, et al. Terms, definitions and measurements to describe sonographic features of myometrium and uterine masses: a consensus opinion from the Morphological Uterus Sonographic Assessment (MUSA) group. Ultrasound Obstet Gynecol 2015.
- Harmsen MJ, et al. MUSA criteria for adenomyosis update. Ultrasound Obstet Gynecol 2022.
- NICE NG73 — Endometriosis: diagnosis and management.
- RCOG Green-top Guideline No. 24 — The Investigation and Management of Endometriosis (historic; superseded by NICE/ESHRE).