Endometriosis — Gynaecology

Definition

Types

Pathogenesis

1. Transplantation/Regurgitation theory (Sampson, 1920s) — most widely accepted. Retrograde menstruation through the fallopian tubes deposits endometrial cells onto pelvic peritoneum. Retrograde menstruation occurs in 70–90% of women but only some develop endometriosis, implying additional host factors are required.
2. Coelomic metaplasia theory — Pelvic mesothelium (sharing embryonic origin with Müllerian ducts) undergoes metaplastic transformation into endometrial tissue.
3. Induction theory / Extrauterine stem cell theory — Bone marrow-derived stem/progenitor cells differentiate into endometrial tissue at ectopic sites.

• Aromatase → increased local oestrogen production
• PGE₂ and other proinflammatory mediators
• VEGF and angiogenic factors
• MMPs (released by recruited macrophages)

Epidemiology & Risk Factors

• Prevalence: ~10% reproductive-age women; up to 50% in women with unexplained infertility
• Economic burden comparable to diabetes mellitus, Crohn's disease, and rheumatoid arthritis (WERF EndoCost study)

Common Sites

• Ovaries (most common)
• Pouch of Douglas / posterior cul-de-sac
• Uterosacral ligaments
• Posterior uterine surface
• Fallopian tubes, broad ligaments
• Rectosigmoid colon (most common extrapelvic site)

Morphology (Pathology)

• Macroscopically: red-brown nodules (active) or white fibrotic plaques (inactive); range from microscopic to 1–2 cm
• Ovarian endometriomas: cysts 3–5 cm, filled with dark "chocolate fluid" (degenerated blood/haemosiderin)
• Chronic bleeding → fibrous adhesions obliterating the pouch of Douglas and distorting anatomy
• Histology (diagnostic standard): endometrial glands + stroma at ectopic site

Clinical Features

Diagnosis

Clinical

• Empirical medical treatment (e.g., hormonal therapy) may precede formal laparoscopic confirmation in patients with classic symptoms and no suspicion of malignancy (ESHRE guideline)

Imaging

• Transvaginal ultrasound (TVS): First-line; excellent for ovarian endometriomas (ground-glass echogenicity, homogeneous). Limited for peritoneal disease.
• MRI: Best for deep infiltrating endometriosis — bowel, bladder, and rectovaginal septum involvement

Laparoscopy

• Gold standard for diagnosis. Allows visual inspection of entire pelvis and histologic confirmation.
• Positive histology confirms; negative histology does not exclude the diagnosis.
• Histologic confirmation recommended for endometriomas >4 cm and deep disease (to exclude malignancy)

Biomarkers

• CA-125 is elevated in some women but has poor sensitivity/specificity — not recommended for routine diagnosis
• Elevated CRP, IL-6, TNF-α in peripheral blood (research tools; not yet standard)

Classification / Staging

rASRM (American Society for Reproductive Medicine)

• Size, appearance, depth of peritoneal/ovarian implants
• Adnexal adhesions
• Cul-de-sac obliteration

Endometriosis Fertility Index (EFI)

• Predicts non-IVF pregnancy rates after surgical staging
• Recommended when future fertility is a concern

ENZIAN Score

• Supplements rASRM for deep endometriosis morphology
• Useful for surgical planning

Medical Management

Key principle: Hormonal drug classes are equally effective for pain relief; selection is guided by side-effect profile, cost, and contraceptive needs. Suppression of ovarian function does NOT improve fertility — medical therapy is not used for infertility management.

Surgical Management

Peritoneal endometriosis

• Ablation or excision equally effective
• Excision preferred when histologic confirmation is desired
• Ablation + adhesiolysis in minimal/mild disease improves fertility vs diagnostic laparoscopy alone

Ovarian endometrioma

• Cystectomy (excision) preferred over drainage + ablation — lower recurrence of pain, endometrioma, and need for reoperation; higher spontaneous pregnancy rates (ESHRE Grade A)
• Intraovarian suture for haemostasis is superior to bipolar coagulation in reducing post-surgical adhesions

Deep infiltrating endometriosis

• Complete surgical excision in a single-stage procedure (multidisciplinary team — gynaecologist, colorectal surgeon, urologist)
• Referral to specialist centre strongly recommended

Definitive surgery

• Total hysterectomy ± bilateral salpingo-oophorectomy (BSO) for women who have completed their family
• BSO reduces recurrence but is not curative in all cases

Endometriosis and Fertility

• Spontaneous abortion rate: Not clearly increased; evidence contradictory
• Assisted reproduction (IVF): Recommended when other treatments fail; ovarian reserve may be reduced by disease and prior surgery

Malignant Transformation

• Risk mainly confined to deep infiltrating endometriosis and ovarian endometriomas
• Associated malignancies: endometrioid carcinoma and clear cell carcinoma of the ovary
• Lifetime risk ~1% in endometrioma patients

Key Takeaways (ESHRE Guidelines)

1. Empirical hormonal therapy is acceptable without surgical diagnosis in classic presentations
2. Laparoscopy is the gold standard for definitive diagnosis
3. Hormonal drug classes are equally effective for pain — choice depends on side effects and patient preference
4. Medical therapy does not improve fertility — surgical removal of lesions does (in minimal/mild disease)
5. Cystectomy is preferred over drainage for endometriomas ≥3 cm
6. Deep DIE requires specialist multidisciplinary surgical management

• Berek & Novak's Gynecology — the standard international reference I used in the previous answer
• Creasy & Resnik's Maternal-Fetal Medicine — focused on obstetrics/high-risk pregnancy