What type of ultrasound is recommended for irregular menstruation?

Ultrasound for Irregular Menstruation

For patients with irregular menstruation, a combined transabdominal and transvaginal ultrasound with Doppler assessment is the most appropriate initial imaging study. 1

Primary Imaging Recommendation

First-Line Imaging:

• Combined transabdominal and transvaginal ultrasound with Doppler assessment
  • Transvaginal component provides detailed visualization of the endometrium and internal structures
  • Transabdominal component ensures complete assessment of an enlarged uterus or uterine tumors that may be incompletely visualized with transvaginal approach alone
  • Doppler evaluation should be considered a standard component of pelvic ultrasound to assess vascularity 1

Timing Considerations

• Ultrasound should be performed during the early follicular phase (days 3-7) of the menstrual cycle when possible
• Avoid performing ultrasound during active menstrual bleeding as this can interfere with proper visualization 2
• Clear documentation of menstrual cycle day is essential for proper interpretation of findings 2

Specific Ultrasound Findings to Assess

Structural Causes:

• Endometrial thickness and pattern (varies with cycle phase in premenopausal women)
• Presence of endometrial polyps
• Submucosal fibroids
• Adenomyosis
• Congenital uterine anomalies

Ovarian Assessment:

• Polycystic ovarian morphology (≥20 follicles per ovary using high-frequency transvaginal probes)
• Ovarian volume (≥10ml is considered abnormal) 1
• Presence of functional cysts or other ovarian pathology

Follow-Up Imaging When Initial Ultrasound is Inconclusive

If the initial ultrasound is inconclusive or further characterization is needed:

1. Sonohysterography (SIS) - particularly useful when focal endometrial abnormality is suspected

   • 96-100% sensitivity and 94-100% negative predictive value for assessing endometrial pathology 1
   • Superior to transvaginal ultrasound alone for detecting submucosal fibroids and polyps 1

2. MRI of the pelvis without and with contrast

   • Indicated when ultrasound cannot adequately visualize the uterus 1
   • Particularly useful for diagnosing adenomyosis, which may be missed on ultrasound if coexisting with fibroids 1

Special Considerations

For Young Patients:

• In patients <8 years post-menarche, multi-follicular ovaries are common and should not be used for diagnosis of PCOS 1
• Transvaginal approach is not recommended in virginal patients; transabdominal imaging should be used instead 1

For PCOS Evaluation:

• Using endovaginal ultrasound transducers with frequency ≥8MHz, the threshold for polycystic ovarian morphology is ≥20 follicles per ovary and/or ovarian volume ≥10ml 1
• With older technology, focus on ovarian volume ≥10ml rather than follicle count 1

Common Pitfalls to Avoid

1. Relying solely on transvaginal or transabdominal approach - both are needed for complete assessment 1
2. Misinterpreting endometrial thickness in premenopausal women - no validated upper limit cutoff exists, and thickness varies with cycle phase 1
3. Performing ultrasound during menstruation, which can lead to suboptimal visualization 2
4. Failing to use Doppler assessment, which is essential for evaluating vascularity of endometrial and myometrial lesions 1

Conclusion

The American College of Radiology clearly recommends combined transabdominal and transvaginal ultrasound with Doppler as the first-line imaging modality for evaluating irregular menstruation, with sonohysterography or MRI as appropriate follow-up studies when initial ultrasound is inconclusive.