Endometriosis

❍ At a glance

• Endometriosis affects approximately 10% of reproductive-age women. The average time from symptom onset to diagnosis is 6-10 years - and that delay happens primarily in primary care, where symptoms are normalised or attributed to primary dysmenorrhoea.
• Classic triad: dysmenorrhoea, deep dyspareunia, subfertility. Also: cyclical pelvic pain preceding menstruation, cyclical bowel symptoms (dyschezia), cyclical bladder symptoms, and significant fatigue.
• A normal pelvic ultrasound does not exclude endometriosis. Peritoneal implants and superficial disease are below the resolution of standard ultrasound. A woman with significant dysmenorrhoea and dyspareunia and a normal scan may well have endometriosis.
• Do not wait for laparoscopy to treat. Empirical hormonal suppression (COCP, progestogen) is appropriate in a woman with clinical features consistent with endometriosis. Refer without waiting for positive imaging.

❍ Presentation: what to look for

The classic triad is dysmenorrhoea, deep dyspareunia, and subfertility - though not all three are present in every case. Additional features that raise suspicion:

• Cyclical pelvic pain that begins days before menstruation and may persist throughout the cycle
• Cyclical bowel symptoms: dyschezia (pain on defecation during menstruation), or cyclical bloating and altered bowel habit
• Cyclical bladder symptoms: dysuria, urgency, haematuria during menstruation
• Non-menstrual chronic pelvic pain
• Significant fatigue - underappreciated as a feature of endometriosis and worth asking about specifically

On examination: tenderness in the pouch of Douglas, uterosacral ligament nodularity, lateral displacement or fixed retroverted uterus, and adnexal tenderness all suggest endometriosis. Examination during menstruation improves sensitivity. The absence of examination findings does not exclude the diagnosis.

❍ Investigation and the normal ultrasound problem

The key fact to internalise: a normal pelvic ultrasound does not exclude endometriosis. Peritoneal implants and superficial disease are below the resolution of standard pelvic ultrasound. Even transvaginal ultrasound by a specialist has limited sensitivity for peritoneal disease. A woman with significant dysmenorrhoea and dyspareunia and a normal scan may well have endometriosis. Do not use a normal ultrasound to close the investigation.

Transvaginal ultrasound is useful for detecting endometriomas (classic appearance: homogeneous low-level internal echoes, "ground glass"), deep infiltrating endometriosis of the rectovaginal septum or bladder, and adenomyosis. An endometrioma on ultrasound is sufficient to confirm ovarian endometriosis and warrants gynaecology referral without further investigation.

CA125 has poor sensitivity and specificity for endometriosis diagnosis in primary care and should not be used to confirm or exclude it. MRI pelvis is more sensitive than ultrasound for deep infiltrating disease and is used in surgical planning by gynaecology - not a primary care first-line investigation.

Definitive diagnosis requires laparoscopy with histological confirmation. This is the gold standard. However, it is not required before starting empirical treatment.

❍ Empirical management in primary care

Do not wait for laparoscopy to initiate treatment. Empirical hormonal suppression is appropriate where clinical features are consistent with endometriosis and there are no contraindications. This provides meaningful symptom relief while awaiting specialist review and does not significantly delay diagnosis.

NSAIDs: first-line analgesia for dysmenorrhoea, taken from before onset of menstruation. Effective for mild symptoms; insufficient alone for moderate-severe disease.

Combined oral contraceptive pill: suppresses endometrial implant stimulation. Continuous cycling (no pill-free interval) may provide better pain control than cyclic use. First-line hormonal option in primary care.

Progestogen-only methods: the levonorgestrel IUS (Mirena) is highly effective for endometriosis-associated pain and heavy menstrual bleeding. The desogestrel POP (Cerazette) is an alternative. Norethisterone 5 mg twice daily can be used for more aggressive suppression in women awaiting surgery. Dienogest (trialled specifically in endometriosis) is available in NZ but not funded.

GnRH agonists (leuprorelin, nafarelin) produce pseudo-menopause through profound oestrogen suppression. Very effective but cause significant menopausal side effects; used by specialists pre- or post-operatively, not as primary care first-line.

❍ Fertility, staging, and referral

Approximately 30-40% of women with endometriosis have difficulty conceiving. The mechanism is multifactorial: altered pelvic anatomy from adhesions, endometrioma affecting ovarian reserve, impaired implantation, and tubal damage. Women with endometriosis who wish to conceive should be referred to a fertility specialist early - fertility surgery may improve natural conception rates, and IVF outcomes are comparable to other indications once appropriate surgical preparation is complete.

ASRM staging (I-IV, minimal to severe) is a surgical finding that correlates poorly with symptom severity. Stage I disease can cause severe pain; stage IV may present primarily with subfertility. Staging shapes surgical and fertility decisions - it is not a primary care diagnostic tool, but knowing it exists helps interpret specialist correspondence.

Refer to gynaecology for: suspected endometriosis where empirical medical management provides inadequate symptom control; endometrioma identified on ultrasound; suspected deep infiltrating endometriosis (severe dyschezia, cyclical haematuria, uterosacral nodularity on examination); subfertility in the context of endometriosis; and where diagnostic laparoscopy is being considered. The referral does not need to wait for positive imaging.