Imaging for Uterine Fibroids
Combined transabdominal and transvaginal ultrasound with Doppler is the first-line imaging modality for diagnosing uterine fibroids, with MRI reserved for complex cases requiring detailed mapping or when ultrasound findings are inconclusive. 1, 2
Initial Imaging Approach
Start with pelvic ultrasound combining both transabdominal (TAUS) and transvaginal (TVUS) approaches with Doppler imaging. 1, 2
TVUS provides superior contrast and spatial resolution with 90-99% sensitivity for detecting fibroids and 90% sensitivity with 98% specificity for submucosal fibroids specifically. 1, 2
TAUS is essential for evaluating significantly enlarged fibroid uteri or large subserosal/pedunculated fibroids that may be poorly visualized on TVUS due to limited field-of-view. 1
Color Doppler should be routinely incorporated to evaluate internal vascularity and identify the "bridging vessel sign" that differentiates subserosal fibroids from extrauterine tumors. 1
Three-dimensional ultrasound with Doppler demonstrates high accuracy (93% sensitivity, 96% specificity) for differentiating fibroids from adenomyosis. 1, 3
Advanced Ultrasound Techniques
Add saline infusion sonohysterography (SIS) when submucosal fibroids are suspected or when evaluating the endometrial cavity. 2
SIS combined with 2-D TVUS achieves 94% sensitivity and 81% specificity for diagnosing submucosal fibroids, with good agreement (kappa 0.80) with diagnostic hysteroscopy. 1, 2
SIS accurately depicts the percentage intracavitary component of submucosal fibroids, which directly impacts treatment decisions. 1
US elastography/sonoelastography can increase diagnostic accuracy by showing fibroids as well-delineated dark areas (due to stiffer smooth muscle) versus adenomyosis appearing as brighter irregular lesions. 1
When to Use MRI
Order pelvic MRI with gadolinium contrast for complex cases, surgical planning, or when ultrasound is inadequate. 1, 2
MRI excels at identifying and mapping fibroids, providing superior information about size, number, location, vascularity, and characterization (classic, degenerated, cellular, or atypical). 1, 3, 2
MRI can differentiate fibroids from adenomyosis and endometriosis, which often cause similar symptoms. 1, 2
MRI with diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) values is critical when distinguishing fibroids from sarcomas, achieving 83-88% sensitivity and 97-100% specificity using diagnostic algorithms. 1
MRI with gadolinium contrast evaluates fibroid viability, uterine artery anatomy, and detects collateral ovarian supply—crucial information for planning embolization procedures. 3
Up to 20% of embolization candidates have non-viable or autoinfarcted fibroids that won't respond to treatment, making MRI essential for identifying these cases. 3
What NOT to Use
CT pelvis (with or without IV contrast) has no role as initial imaging for clinically suspected fibroids—there is no relevant literature supporting its use. 1
Critical Pitfalls to Avoid
Relying solely on TVUS for large fibroids or enlarged uteri will miss important findings due to limited penetration depth—always combine with TAUS. 1, 2
Failing to use SIS when evaluating submucosal fibroids leads to inadequate assessment of fertility impact and treatment planning. 2
Not obtaining MRI in cases with multiple fibroids results in incomplete evaluation and can alter management in up to 28% of patients. 3
TAUS limitations include poor acoustic windows from decompressed bladder, retroverted uterus, large body habitus, and bowel gas—recognize these scenarios and adjust technique accordingly. 1
TVUS limitations include limited depth of penetration and shallow focal length that restrict evaluation of large or subserosal/pedunculated fibroids—use TAUS to compensate. 1