Ultrasound Evaluation of Irregular Menses

Imaging Modalities

• The American College of Radiology recommends transvaginal ultrasound as the first-line imaging modality, combined with transabdominal ultrasound for complete assessment of pelvic structures in patients with irregular menses 1, 2, 3
• Transvaginal ultrasound provides superior resolution for detailed assessment, while transabdominal ultrasound offers a broader overview and is necessary for enlarged structures 1, 4, 2, 3
• A combined transabdominal and transvaginal approach is essential to ensure complete assessment of ovaries, as recommended by the American College of Radiology and the Society of Radiologists in Ultrasound 5
• Transvaginal approach is not recommended in virginal patients; transabdominal imaging should be used instead, while transvaginal ultrasound approach is preferred if sexually active and acceptable to the patient 6, 7

Endometrial Evaluation

• In premenopausal women, abnormal echogenicity and texture of the endometrium correlate with underlying pathology, although no validated upper limit cutoff for endometrial thickness exists 1
• The sensitivity and specificity of ultrasound for detecting adenomyosis are 82.5% and 84.6%, respectively, with characteristics including heterogeneous myometrium, myometrial cysts, and asymmetric thickening of the anterior or posterior wall 1
• Simple cysts up to 3 cm in diameter are considered benign and require no further follow-up, according to the American College of Radiology 5
• Simple cysts up to 10 cm in diameter are likely benign and can be safely monitored, according to the American College of Radiology 5
• The American College of Radiology recommends follow-up ultrasound in one year for simple cysts >3 cm but <10 cm, and consideration of annual follow-up for up to 5 years if stable 5

Doppler Assessment and Timing Considerations

• Doppler assessment is an essential component of pelvic ultrasound, helping to distinguish fluid from vascular soft tissue and evaluate the vascularity of endometrial and myometrial lesions, with a specificity of 62-98% for endometrial polyps 1, 3
• Documenting the day of the menstrual cycle during examination is important, and sonohysterography may be considered for further evaluation of focal endometrial abnormalities 1
• Women with dysmenorrhea should not undergo ultrasound during menses, as this timing can interfere with proper visualization and diagnostic accuracy, highlighting the importance of proper timing and clear documentation of menstrual cycle day 1, 7

Coexisting Pathologies

• The detection of adenomyosis is limited when coexisting with leiomyomas, with sensitivity dropping from 97.8% to 33.3%, highlighting the need for careful evaluation of multiple pathologies 1
• Ovarian volume of ≥10ml is considered abnormal, and polycystic ovarian morphology is defined as ≥20 follicles per ovary using high-frequency transvaginal probes 7

Cephalopelvimetry and Pelvic Adequacy

• Cephalopelvimetry is essential to exclude the presence of cephalopelvic disproportion (CPD) and should be considered in the assessment of pelvic adequacy 8
• Risk factors for CPD, including maternal diabetes and obesity, abnormal pelvic shape or size, fetal macrosomia, malposition, malpresentation, asynclitism, and excessive molding, should be taken into account when determining pelvic adequacy 8
• Labor pattern abnormalities, such as prolonged deceleration phase or protracted active phase, may indicate underlying CPD and should be carefully monitored 8
• If normal pelvic dimensions and no risk factors are present, plans for vaginal delivery can proceed 8
• If evidence of CPD is found, cesarean delivery is the safer choice 8
• If uncertain, err on the side of caution with cesarean delivery, as the risks of attempting vaginal delivery with CPD are significant 8

Follow-up and Referral

• Referral to gynecology is recommended if the cyst enlarges, as suggested by the American College of Radiology 5
• Regular gynecologic follow-up is recommended for all women with a history of hysterectomy, according to the American Society of Clinical Oncology 9
• Women with one remaining ovary should continue regular gynecologic follow-up, as recommended by the American Society of Clinical Oncology 9

Imaging Modality Comparison Table