Key Facts

Dysmenorrhoea is painful menstruation, classified as primary (functional) or secondary (pathological). It is extremely common and a significant cause of morbidity and reduced quality of life in women of reproductive age.

Epidemiology

• Primary dysmenorrhoea: up to 90% of adolescents; typically begins within 1-2 years of menarche
• Secondary dysmenorrhoea: more common from mid-20s onwards
• Leading cause of recurrent short-term school/work absence in young women
• 10-15% of women report severe dysmenorrhoea that interferes with daily activities

Aetiology

• Primary: excessive endometrial prostaglandin production (PGF2α and PGE2) during menstruation
• Secondary: endometriosis (most common), adenomyosis, fibroids (particularly submucosal), pelvic inflammatory disease, endometrial polyps, ovarian cysts, cervical stenosis, copper IUD

Pathophysiology

• Primary: prostaglandins cause myometrial hypercontractility, uterine ischaemia, and sensitisation of pain nerve endings
• Prostaglandins also cause systemic symptoms: nausea, vomiting, diarrhoea, headache
• Secondary: depends on underlying cause (e.g. endometrial implants in endometriosis cause cyclic inflammation and adhesions)

Primary Dysmenorrhoea

• Crampy, colicky suprapubic pain beginning hours before or at onset of menstruation
• Typically lasts 48-72 hours
• May radiate to lower back and inner thighs
• Associated symptoms: nausea, vomiting, diarrhoea, headache, fatigue
• Onset within 1-2 years of menarche
• Normal pelvic examination

Secondary Dysmenorrhoea

• Pain may begin before menstruation and persist after it ends
• Progressive worsening over months-years
• Deep dyspareunia
• Non-menstrual pelvic pain
• Heavy menstrual bleeding
• Abnormal findings on pelvic examination

Red Flags

• Onset of dysmenorrhoea after age 25 (secondary cause)
• Progressively worsening pain
• Deep dyspareunia
• Intermenstrual or postcoital bleeding
• Abnormal vaginal discharge (PID)
• Failed response to NSAIDs and hormonal treatment

Bedside

• Abdominal and pelvic examination (may be normal in primary dysmenorrhoea)
• Speculum examination if secondary cause suspected
• STI screening if PID suspected

Bloods

• Not routinely required for primary dysmenorrhoea
• FBC if associated HMB
• CRP, WCC if PID suspected
• CA-125: may be elevated in endometriosis (not diagnostic; sensitivity 25-50%)

Imaging

• Pelvic USS (TVS): first-line if secondary cause suspected; can identify fibroids, ovarian endometriomas, adenomyosis
• MRI pelvis: for adenomyosis diagnosis and endometriosis staging

Special Tests

• Laparoscopy: gold standard for endometriosis diagnosis (allows simultaneous treatment)
• Hysteroscopy: if intrauterine pathology suspected

Non-pharmacological

• Heat therapy: topical heat pads (evidence shows equivalent to ibuprofen in some studies)
• Exercise: regular physical activity reduces severity
• TENS: transcutaneous electrical nerve stimulation (limited evidence)
• Lifestyle: adequate sleep, stress management, dietary omega-3

Pharmacological

• First-line: NSAIDs
  • Ibuprofen 400mg TDS (start before or at onset of menses)
  • Mefenamic acid 500mg TDS (also reduces menstrual blood loss)
  • Naproxen 250-500mg BD
• Second-line: Combined hormonal contraception
  • COC pill (can be used continuously to avoid withdrawal bleeds)
  • Combined patch or vaginal ring
• Third-line:
  • Mirena IUS (particularly effective for secondary dysmenorrhoea)
  • Depo-Provera
  • GnRH analogues (for severe endometriosis-related pain; with add-back HRT)
• Adjuncts: paracetamol, codeine for breakthrough pain

Surgical/Interventional

• Laparoscopic excision/ablation of endometriosis: for secondary dysmenorrhoea due to endometriosis
• Presacral neurectomy: for midline pain in severe dysmenorrhoea (rarely performed)
• Hysterectomy with BSO: definitive for severe adenomyosis/endometriosis if family complete

Referral Criteria

• Failure to respond to NSAIDs and hormonal treatment after 3-6 months
• Suspected endometriosis: gynaecology referral for laparoscopy
• Secondary dysmenorrhoea with abnormal imaging
• Impact on quality of life despite treatment

• Primary dysmenorrhoea often improves with age and after childbirth
• NSAIDs provide effective relief in 70-80% of women with primary dysmenorrhoea
• Hormonal contraception effective in >90% when combined with NSAIDs
• Endometriosis-related dysmenorrhoea: chronic condition with variable response to treatment; recurrence after surgery is common (40-50% at 5 years)
• No long-term complications from primary dysmenorrhoea itself

Primary vs Secondary Dysmenorrhoea