First principle: ectopic, cyclically responsive endometrial‑type tissue
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Common sites: ovary, pouch of Douglas, uterosacral ligaments, pelvic peritoneum. Retrograde menstruation with implantation (Sampson) is the classic theory.
Clinical picture and the key discriminator
- Triad: dysmenorrhoea, deep dyspareunia, infertility; also dyschezia, dysuria, cyclical bowel/bladder symptoms.
- *Pain severity does not correlate with disease stage* — small peritoneal lesions can be agonising, large endometriomas silent.
- Exam: fixed retroverted uterus, uterosacral nodularity, adnexal mass (endometrioma).
Investigation — the modern correction 🚩
Management by goal
- Pain: NSAIDs; hormonal suppression (combined hormonal contraception or progestogens; GnRH analogues with add‑back for refractory disease).
- Fertility: do not simply suppress ovulation — assess age, reserve, tubal/semen factors; surgery or ART as indicated.
- Endometrioma: operate for clear benefit, weighing the cost to ovarian reserve.
Adenomyosis — the sibling
Endometrial tissue within the myometrium: dysmenorrhoea + menorrhagia, a bulky, boggy, tender uterus, heterogeneous myometrium on imaging.
| Endometriosis | Adenomyosis | |
|---|---|---|
| Location | outside uterus | within myometrium |
| Classic | pain + infertility, endometrioma | heavy + painful menses, bulky tender uterus |
Pearls
- 🎯 Endometrioma = "chocolate cyst," ground‑glass on US. Pain ≠ stage.
- 🩺 Empirical hormonal therapy for cyclical pelvic pain is legitimate — you need not laparoscope everyone first.
Next → From misplaced endometrium to the commonest benign uterine tumour (Concept 20).