Pathogenesis

It is thought to be due to a release of prostaglandins and leukotrienes in the menstrual fluid, which in turn produces vasoconstriction in the uterine vessels, causing the uterine contractions which produce the pain. The prostaglandin release may also be responsible for gastrointestinal disturbance which may occur in association with dysmenorrhoea.

Classification

Dysmenorrhoea may be thought of as either primary or secondary.

Primary dysmenorrhoea

Primary dysmenorrhoea occurs in young females with no pelvic pathology.

• It often begins with the onset of ovulatory cycles six months to one year after the menarche.^[1]
• The pain begins with the onset of the period and may last for 24-72 hours.

Secondary dysmenorrhoea

Secondary dysmenorrhoea occurs in association with some form of pelvic pathology:

• The pain typically precedes the start of the period by several days and may last throughout the period.
• There may be associated dyspareunia.
• Secondary dysmenorrhoea may occur as a result of:
  • Fibroids
  • Adenomyosis
  • Endometriosis
  • Pelvic inflammatory disease
  • Adhesions
  • Developmental abnormalities

Epidemiology

• Dysmenorrhoea is very common although the precise incidence is not known, as it frequently goes unreported.
• Primary dysmenorrhoea is the most commonly given reason for absence from school amongst adolescent girls and approximately 15% will complain of severe dysmenorrhoea.
• Longer duration of menses, early menarche, smoking. alcohol and obesity are all risk factors associated with dysmenorrhoea.^[1]
• Females who are depressed and/or have poor social support networks are also more likely to experience pain.^[2]

Assessment

A presumptive diagnosis of primary dysmenorrhoea may be made on history ± abdominal examination alone in young patients who are not sexually active, and vaginal examination is not normally required in this group of patients.

Investigation of dysmenorrhoea is primarily aimed at ruling out underlying pathology and may include any or all of the following as appropriate to the individual.

History

• Age at menarche.
• Cycle length.
• Whether the cycle is regular.
• Duration of bleeding.
• Timing of pain in relation to period.
• Smoking history.
• Whether the patient is sexually active.
• Obstetric history.
• Contraceptive history.
• Any features suggestive of underlying pathology (eg vaginal discharge, intermenstrual or postcoital bleeding, dyspareunia).

  Examination

  Abdominal/vaginal examinations are indicated if sexually active:
  • Adenomyosis - the uterus may be enlarged and tender with a typical 'boggy' feel.
  • Endometriosis - generalised tenderness in the pelvic area. The uterus may be fixed ± retroverted due to adhesions, nodules may be palpable in the uterosacral ligaments.
  • Partially imperforate hymen (rare).
  • Vaginal septum (rare).

Additional investigations

• Vaginal examination - if sexually active.
• High vaginal swab, chlamydial swabs.
• Cervical smear.
• Pelvic ultrasound - if uterine enlargement or adnexal mass is present.
• Transvaginal ultrasound.
• MRI scan.
• Laparoscopy.
• Laparotomy with biopsy.

Management

General measures

Patients may be concerned about the possibility of underlying pathology and, when appropriate, reassurance and an explanation of the mechanism of menstrual pain may be helpful.

• Lifestyle changes - longitudinal studies have looked at risk factors for dysmenorrhoea and have found a clear association between smoking and dysmenorrhoea; patients should therefore be informed of this relationship and assisted in any attempts to stop smoking.^[3]
• Self-help techniques - anecdotally, many women find the following measures to be helpful in relieving the symptoms of dysmenorrhoea:
  • Tea - regular, camomile or mint.
  • Warmth to the abdomen.
  • A warm bath.
  • Abdominal and/or back massage.
  • Lying in the supine position.
• Complementary and alternative medicines - several dietary supplements and herbal remedies have been suggested but there is insufficient evidence to recommend any of them.^[4] They include calcium and magnesium, thiamine, ginger,^[5] fish oil supplements, toki-shakuyaku-san (TSS) - a Japanese herbal remedy, transcutaneous electrical nerve stimulation (TENS), acupuncture and acupressure.

Pharmacological

• Non-steroidal anti-inflammatory drugs (NSAIDs) - these are the most commonly used drugs for the treatment of dysmenorrhoea due to their inhibition of prostaglandin synthesis. This is a class effect and all NSAIDs appear equally effective.^[6] Ibuprofen is most often used due to its low incidence of side-effects. Adolescents and young adults with symptoms that do not respond to treatment with NSAIDs for three menstrual periods should be offered combined oral contraceptive pills (COCPs) for three menstrual cycles.^[7]
• Oral contraceptive pills (OCPs) - these are also used. It is thought that the mechanism of action is reduced prostaglandin release during menstruation. OCPs may be given by the oral or vaginal route for the treatment of dysmenorrhoea - the vaginal route having fewer systemic side-effects and greater analgesic effect.^[8] Despite the common use of OCPs in the treatment of dysmenorrhoea (and guidance from the Faculty of Sexual and Reproductive Healthcare stating it can be used for this purpose from the menarche), previous evidence has been inconclusive, due to a lack of evidence from randomised control trials.^[9] OCPs can also be used to increase cycle length and therefore reduce the frequency of the symptoms.
  
  Adolescents and young adults who do not respond to this treatment should be evaluated for secondary causes of dysmenorrhoea.^[7] This is likely in approximately 10% of patients.
• Depo-medroxyprogesterone acetate (Depo-Provera®) - is also sometimes used, as many women become amenorrhoeic within a year of starting treatment.
• Mirena® - there is some evidence to suggest that use of the levonorgestrel intrauterine contraceptive device (Mirena®) may be of use in some women.
• Danazol - this may be used occasionally, with specialist supervision, in the treatment of severe refractory cases.
• Leuprolide acetate - may be used in rare cases to suppress the menstrual cycle, but has a significant side-effect profile.

Surgery

• Laparoscopic uterine nerve ablation (LUNA) has been used for the treatment of severe refractory cases; however, a Cochrane meta-analysis concluded that there is insufficient evidence of its effectiveness to recommend the procedure.^[10][11]
• Hysterectomy - in severe refractory cases, particularly in women who feel they have completed their families, hysterectomy may be considered.