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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Endometrial-like tissue outside the uterus — responds to cyclical hormonal changes → bleeding, inflammation, adhesions
- Affects ~10% of women of reproductive age. Average diagnostic delay of 7–8 years
- Classic triad: cyclical pelvic pain, dysmenorrhoea, deep dyspareunia. Also dyschezia, subfertility
- Diagnosis: clinical suspicion. Definitive diagnosis by laparoscopy (gold standard) with histological confirmation
- Medical: hormonal — COCP, progestogens, LNG-IUS, GnRH agonists. Aim to suppress oestrogen-driven growth
- Surgical: laparoscopic excision/ablation of deposits. Endometriomas >3 cm — excise capsule
Overview
Endometriosis is a chronic, oestrogen-dependent condition characterised by the presence of endometrial-like tissue (glands and stroma) outside the uterine cavity. The most common sites are the ovaries (forming endometriomas/"chocolate cysts"), pelvic peritoneum, uterosacral ligaments, pouch of Douglas, and rectovaginal septum. Less commonly, it can affect the bladder, bowel, diaphragm, and surgical scars. The exact aetiology is unknown, but the most widely accepted theory is retrograde menstruation (Sampson's theory) combined with immune dysfunction and genetic predisposition.
Epidemiology
Endometriosis affects approximately 10% of women of reproductive age, equating to ~1.5 million women in the UK. It is found in 25–50% of women investigated for subfertility and 70–80% of women with chronic pelvic pain. The average delay from symptom onset to diagnosis is 7–8 years in the UK. Risk factors include nulliparity, early menarche, short menstrual cycles, heavy periods, and family history (6x risk if first-degree relative affected). Symptoms typically improve after menopause as oestrogen levels decline.
Clinical Features
Symptoms
Chronic pelvic pain — cyclical, worsening before and during menstruation
Secondary dysmenorrhoea — progressively worsening period pain, often starting before bleeding
Deep dyspareunia — pain during or after intercourse, especially deep penetration
Dyschezia — pain on defecation, especially during menstruation (rectovaginal endometriosis)
Subfertility — present in 30–50% of women with endometriosis
Cyclical dysuria or haematuria (bladder endometriosis)
Cyclical rectal bleeding (bowel endometriosis)
Fatigue and mood disturbance
Signs
Fixed retroverted uterus (adhesions tethering uterus posteriorly)
Tenderness and nodularity in the posterior fornix or uterosacral ligaments on bimanual examination
Adnexal mass (endometrioma)
Reduced uterine mobility on bimanual examination
Visible endometriotic deposits in posterior fornix or on cervix (rare)
Investigations
First-line
Clinical history and examinationSuspect endometriosis if cyclical pelvic pain, dysmenorrhoea, deep dyspareunia, subfertility. Clinical diagnosis often sufficient to start empirical treatment
Pelvic USS (TVUSS)Can identify endometriomas (ground-glass appearance "chocolate cysts") and deep infiltrating endometriosis. Cannot reliably detect peritoneal disease
Second-line
MRI pelvisFor deep infiltrating endometriosis (DIE) — rectovaginal, uterosacral, bladder. Helps surgical planning
CA-125May be mildly elevated in endometriosis but NOT diagnostic — too non-specific. Do not use for diagnosis (NICE NG73)
Specialist
LaparoscopyGold standard for definitive diagnosis. Allows visualisation, biopsy, and simultaneous treatment (excision/ablation). Powder-burn, red, white, and clear vesicle lesions may all represent endometriosis
1
Analgesia
- Paracetamol and/or NSAIDs (e.g., mefenamic acid, ibuprofen) — first-line for pain
- Avoid long-term opioid use — risk of dependence
2
Hormonal treatment
- COCP (continuous or tricyclic — to suppress menstruation and reduce oestrogen stimulation)
- Progestogens: medroxyprogesterone acetate, norethisterone, desogestrel POP
- LNG-IUS (Mirena) — particularly useful for associated HMB
- GnRH agonists (e.g., goserelin, leuprorelin): induce temporary menopause. Use with HRT "add-back" therapy. Max 6 months without add-back (bone loss)
- All hormonal treatments are contraceptive — cannot be used if trying to conceive
3
Surgical treatment
- Laparoscopic excision (preferred over ablation) of endometriotic deposits
- Endometriomas >3 cm: excision of cyst capsule (cystectomy) is preferred over drainage/ablation
- Deep infiltrating endometriosis: specialist centre referral — may require bowel/bladder surgery
- Hysterectomy ± bilateral salpingo-oophorectomy: consider if medical and conservative surgical treatment has failed and family is complete. Recurrence still possible if ovaries retained
4
Fertility management
- Refer to fertility specialist if not conceiving after 6–12 months
- Surgical excision of endometriosis may improve spontaneous conception rates
- Assisted reproduction (IVF) — may be necessary, particularly in moderate-severe disease
- Hormonal treatment does NOT improve fertility — only suppresses disease activity
Complications
- Subfertility: Due to adhesions, tubal damage, distorted anatomy, and inflammatory environment
- Endometrioma rupture: Acute pelvic pain — may mimic ectopic pregnancy or torsion
- Adhesions: Can cause chronic pain, bowel obstruction, and surgical difficulty
- Psychological impact: Depression, anxiety, relationship difficulties — from chronic pain and subfertility
- Malignant transformation: Very rare — endometriosis-associated ovarian cancer (clear cell, endometrioid)
UKMLA Exam Tips
- 1Classic triad: cyclical pelvic pain + dysmenorrhoea + deep dyspareunia. Think endometriosis
- 2CA-125 is NOT diagnostic for endometriosis — do not use it for diagnosis
- 3Laparoscopy is the gold standard for definitive diagnosis
- 4Hormonal treatment suppresses disease but does NOT improve fertility
- 5Endometrioma = "chocolate cyst" — ground-glass appearance on USS
- 6GnRH agonists: max 6 months without add-back HRT (bone density loss)
- 7Average diagnostic delay is 7–8 years — consider endometriosis early in young women with cyclical pain
practicetest your knowledge on endometriosisApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — obstetrics and beyond.
open q-bank