Investigation of Secondary Dysmenorrhoea
Begin with transvaginal ultrasound using an expanded protocol as the first-line imaging modality, which has 82.5% sensitivity and 84.6% specificity for detecting endometriosis, the leading cause of secondary dysmenorrhoea. 1
Clinical Assessment
The diagnostic workup should focus on distinguishing secondary from primary dysmenorrhoea through specific clinical features:
- Progressive worsening of menstrual pain over time (not static pain intensity) 1
- Pain extending beyond the menstrual period (not confined to menses only) 1
- Associated infertility (present in approximately 50% of endometriosis cases) 1
- Failure to respond to 3-6 months of empiric treatment with NSAIDs and hormonal contraceptives 2
A pelvic examination should assess for pelvic masses, nodularity in the posterior cul-de-sac, and fixed uterine retroversion, though physical examination alone is insufficient for diagnosis. 1
Laboratory Testing
Obtain a pregnancy test (β-hCG) in all reproductive-aged women before proceeding with imaging. 3 This is essential to avoid radiation exposure and to identify ectopic pregnancy as an alternative diagnosis.
No other routine laboratory tests are specifically indicated for secondary dysmenorrhoea investigation unless clinical features suggest alternative diagnoses (e.g., complete blood count if heavy bleeding is present). 3
Imaging Protocol
First-Line: Transvaginal Ultrasound
Transvaginal ultrasound with expanded protocol is the recommended initial imaging study. 1 This modality can:
- Detect endometriomas with high accuracy 4
- Assess ovarian reserve (antral follicle count, ovarian volume) 4
- Identify other pelvic pathology (fibroids, adenomyosis) 1
Second-Line: MRI Pelvis
Order MRI pelvis without and with contrast if ultrasound findings are inconclusive or for surgical planning. 1 MRI offers:
- 82-90% sensitivity and 91-98% specificity for endometriomas 4
- Superior detection of deep infiltrating endometriosis 5
- Excellent visualization of adhesions (low-signal intensity bands, obliteration of organ interfaces) 5
CT scanning is not recommended for routine evaluation of secondary dysmenorrhoea, as it provides inferior soft tissue characterization compared to MRI and involves radiation exposure. 3
Role of Laparoscopy
Laparoscopy with histologic confirmation is no longer required before initiating empiric treatment for suspected endometriosis. 1 However, diagnostic laparoscopy remains indicated when:
- Medical management fails after adequate trial 2
- Surgical intervention is planned 5
- Diagnosis remains uncertain after imaging 4
Important caveat: Endometriotic lesions in adolescents and young women appear different than in adults—typically clear or red rather than the classic "powder burn" appearance—requiring expertise in recognizing atypical presentations. 2
Exclusion of Alternative Diagnoses
The workup should systematically exclude:
- Adenomyosis: More common in older, multiparous women; MRI shows thickened junctional zone 1
- Chronic pelvic inflammatory disease: Acute/subacute onset, not progressive worsening; consider if risk factors present 1
- Ovarian masses: Ruled out by ultrasound imaging 3
- Uterine fibroids: Identified on ultrasound; typically cause heavy bleeding more than dysmenorrhoea 1
Common Pitfalls
- Do not delay imaging while pursuing prolonged empiric therapy. If symptoms persist beyond 3-6 months of treatment, proceed with imaging workup. 2
- Do not assume normal ultrasound excludes endometriosis. Small peritoneal implants may not be visible on any imaging modality and require laparoscopy for diagnosis. 4
- Do not order CT scan as first-line imaging for dysmenorrhoea evaluation—it provides inferior information compared to ultrasound or MRI and involves unnecessary radiation. 3
- Do not forget that up to 44% of women experience symptom recurrence within one year after surgery, so imaging findings must be interpreted in the context of treatment planning. 5, 4