How can I differentiate between primary and secondary dysmenorrhoea during a patient consultation?

To differentiate between primary and secondary dysmenorrhoea during a patient consultation, focus on the history, symptom onset, and clinical features:

• Primary dysmenorrhoea typically presents as menstrual pain without any identifiable underlying pelvic pathology, usually starting within a few years of menarche and often associated with ovulatory cycles.
• Secondary dysmenorrhoea is menstrual pain caused by an underlying pelvic pathology such as endometriosis, fibroids, or pelvic inflammatory disease. It often begins after several years of painless periods or is associated with other symptoms.
• Ask about the onset and pattern of pain: if menstrual pain started after several years of painless periods or worsens over time, suspect secondary causes.
• Look for 'red flags' indicating serious secondary causes, including positive pregnancy test with pelvic pain and bleeding, ascites or pelvic/abdominal mass (not due to fibroids), abnormal cervix on examination, persistent intermenstrual or postcoital bleeding without PID features, or ultrasound suggestive of cancer. These require urgent referral.
• Assess for associated symptoms such as deep dyspareunia, abnormal vaginal discharge, or cyclical gastrointestinal or urinary symptoms, which may suggest endometriosis or other secondary causes.
• Perform a pelvic examination to identify abnormalities such as pelvic masses, tender nodularity, or abnormal cervix.
• If symptoms are severe, atypical, or do not respond to initial treatment within 3–6 months, consider referral to a gynaecologist for further assessment.

In summary, primary dysmenorrhoea is a diagnosis of exclusion characterized by typical menstrual pain without other pelvic pathology, whereas secondary dysmenorrhoea involves identifiable pelvic disease, later onset, and additional symptoms or signs on examination or investigation ¹.