Dysmenorrhoea (Primary & Secondary)

Painful menstruation — one of the commonest gynaecological presentations (reported by ~45–95% of menstruating people, up to ~93% of adolescents). It is the leading cause of recurrent short-term school/work absence in this age group, yet most who experience it never consult — screen for it rather than waiting for it to be raised. The central task is distinguishing primary (no underlying pathology, ~90% of cases) from secondary (an identifiable cause, ~10%).

Endometriosis and adenomyosis — the leading structural causes of secondary dysmenorrhoea — now have their own pages: Endometriosis and Adenomyosis.

Primary dysmenorrhoea

Prostaglandin-driven crampy pelvic pain with no underlying pathology.

• Demographics: ~95% of adolescents, ~50% of women. Risk factors: menarche <12, age <30, longer/heavier flow, smoking, obesity.
• Typical picture: onset 6–12 months after menarche (ovulatory cycles established); crampy lower-abdominal/pelvic pain radiating to back or thighs, starting just before or with menses and lasting ~8–72 hours (max at the start, easing over 1–3 days). Systemic symptoms are common — nausea, vomiting, diarrhoea, fatigue, bloating, headache.
• No examination or investigation is needed if the history is typical and there is a good response to first-line treatment.

Secondary dysmenorrhoea

Period pain due to underlying pathology. Causes: endometriosis (commonest), adenomyosis, pelvic inflammatory disease, fibroids, endometrial/endocervical polyps, non-hormonal (copper) IUD, pelvic actinomycosis, congenital outflow abnormalities.

Features that point to a secondary cause

• Onset in the third decade or later (or pain that changed in pattern), rather than soon after menarche.
• Dyspareunia, heavy menstrual bleeding, intermenstrual or post-coital bleeding.
• Irregular periods.
• Poor response to a 3-month trial of first-line treatment.
• Relevant family history (endometriosis, gynaecological cancer).

Assessment of suspected secondary dysmenorrhoea

• Characterise the pain (severity, cyclic vs non-cyclic, relation to menses) and associated symptoms (PMS, menorrhagia, dyspareunia, bowel/bladder/musculoskeletal).
• Gynaecological, sexual, psychological and social history; effect on daily life.
• Pelvic ultrasound (transvaginal preferred; transabdominal if not yet sexually active) for anyone with moderate–severe symptoms, ideally by an experienced gynaecological sonographer. Remember a normal scan does not exclude endometriosis.
• Cervical screening if due; STI swabs if appropriate; pelvic examination (omit if not yet sexually active).
• If endometriosis is suspected, move to the Endometriosis pathway for management and referral timing.

An incidental polycystic ovarian appearance on ultrasound is normal for up to ~8 years post-menarche and, in an adolescent, does not by itself warrant investigation or a PCOS/PMOS label.

Management (applies to primary; treat the cause in secondary)

Shared decision-making, factoring in the patient’s preferences and fertility plans.

First-line — NSAIDs. All available NSAIDs are of comparable efficacy; they work by inhibiting prostaglandin synthesis.

• Start 1–2 days before expected menses and continue on a regular schedule through the first 2–3 days of bleeding (peak prostaglandin period) — not just at pain onset.
• A higher loading dose followed by a lower scheduled dose gives better pain scores than a flat regimen. Emphasise the regimen — only ~⅓ of young patients take the recommended dose.
• Examples: ibuprofen 200–400 mg TDS, naproxen 500 mg then 250 mg 6–8-hourly (max 1250 mg/24 h), mefenamic acid 500 mg TDS. GI upset → take with food or use a COX-2 inhibitor. Up to ~20% get minimal relief.

First-line — hormonal therapy (offer to those not currently seeking pregnancy, unless contraindicated):

• Combined hormonal contraception (COC or vaginal ring) is effective in up to ~90%. Continuous or extended use is preferred over cyclical — it minimises withdrawal bleeding and better controls pain. (Mind VTE risk/contraindications.)
• Progestogen-only options also work — the 52 mg LNG-IUD (improves both primary and secondary dysmenorrhoea, safe in nulliparous and adolescent patients), the etonogestrel implant, and DMPA. Irregular bleeding is common. Useful when oestrogen is contraindicated or a user-independent method is preferred.

Adjuncts / non-pharmacological: local heat (hot water bottle/heat pack — evidence comparable to NSAIDs), exercise, TENS. Ginger has reasonable evidence (anti- inflammatory + anti-emetic). Other supplements (vitamin E, thiamine, pyridoxine, magnesium, fish oil, acupressure/acupuncture) show small or inconsistent benefit.

Escalate / reconsider secondary cause if onset was >12 months post-menarche, the pain pattern changed, or there is a poor response to a 3-month trial — refer earlier if endometriosis is suspected, given the fertility implications.