What is the recommended initial imaging modality for a female patient of reproductive age presenting with symptoms suggestive of uterine fibroids, such as heavy menstrual bleeding, pelvic pain, or pressure?

Imaging for Diagnosis of Uterine Fibroids

Recommended Initial Imaging

Transvaginal ultrasound combined with transabdominal ultrasound is the first-line imaging modality for diagnosing uterine fibroids, with sensitivity of 90-99% and specificity of 98%. 1

The American College of Radiology designates this combined ultrasound approach as "Usually Appropriate" for initial evaluation of clinically suspected fibroids. 1 The combination is superior to either modality alone because:

• Transvaginal ultrasound (TVUS) provides higher contrast and spatial resolution for detailed evaluation of the uterus and should be performed whenever possible 1
• Transabdominal ultrasound (TAUS) is essential for significantly enlarged fibroid uteri or large subserosal/pedunculated fibroids that may be poorly visualized on TVUS due to limited field-of-view 1

When to Add Doppler

Three-dimensional ultrasound with Doppler should be incorporated when available, as it demonstrates high accuracy (93% sensitivity, 96% specificity) in differentiating fibroids from adenomyosis, which frequently coexists and complicates the clinical picture. 1

Advanced Imaging: When MRI is Indicated

MRI is not appropriate for initial imaging but becomes "Usually Appropriate" in specific clinical scenarios 1:

• Multiple fibroids requiring precise surgical mapping - MRI excels at identifying exact number, size, and location of all fibroids 1
• Differentiation from adenomyosis or endometriosis when ultrasound findings are equivocal 1
• Preoperative planning when detailed anatomic relationships are needed 1
• Suspected atypical features requiring characterization of fibroid vascularity and degeneration patterns 1

When MRI is performed, gadolinium-based IV contrast is preferred for optimal identification of fibroid vascularity and characteristics. 1

Specialized Ultrasound Techniques

Saline infusion sonohysterography (SIS) should be considered specifically when submucosal fibroids are suspected, as it improves visualization and differentiation between endometrial pathologies and submucosal fibroids. 2 This technique shows moderate interobserver agreement for submucosal fibroid assessment. 1

Ultrasound elastography/sonoelastography is an emerging technique that measures tissue strain and has shown:

• Increased diagnostic accuracy in identifying fibroids versus adenomyosis 1
• Fibroids appear as well-delineated dark areas (due to stiffer compressed smooth muscle) 1
• Excellent agreement with MRI-based diagnosis 1

What NOT to Use Initially

CT pelvis (with or without IV contrast) is "Usually Not Appropriate" for initial imaging of suspected fibroids, as there is no relevant literature supporting its use in this context. 1 CT should be reserved for evaluating acute complications when they occur. 3

Critical Pitfalls to Avoid

• Do not rely solely on TVUS for large fibroids or enlarged uteri - always complement with TAUS to avoid missing subserosal or pedunculated fibroids 2
• Do not perform inadequate assessment of submucosal fibroids - these specifically affect fertility and cause abnormal bleeding, requiring SIS if suspected 2
• Do not assume ultrasound alone is sufficient for complex cases - when multiple fibroids are present or surgical planning is needed, MRI provides superior delineation 2
• In postmenopausal women with fibroids, maintain high suspicion for malignancy - endometrial biopsy is essential prior to intervention 3

Diagnostic Accuracy Comparison

While ultrasound is the appropriate initial modality, the relative performance of imaging modalities shows:

• Ultrasound: 88.2% sensitive, 66.7% specific, 85.0% accurate 4
• MRI: 97.1% sensitive, 83.3% specific, 95.0% accurate 4

This superior accuracy of MRI justifies its use in complex cases but does not change the recommendation for ultrasound as the initial diagnostic approach. 1, 4