What is the recommended imaging for diagnosing fibroids?

Recommended Imaging for Diagnosing Uterine Fibroids

Pelvic ultrasound (transabdominal and transvaginal) with Doppler and MRI with and without intravenous contrast are the best imaging modalities for the initial diagnosis of fibroids. 1

First-Line Imaging: Ultrasound

Transvaginal Ultrasound (TVUS)

• TVUS provides higher contrast and spatial resolution and should be combined with transabdominal ultrasound whenever possible 1
• Demonstrates high sensitivity (90-99%) and specificity (98%) for detecting uterine fibroids, particularly submucosal fibroids 1
• On ultrasound, fibroids typically appear as well-defined, solid, concentric, hypoechoic masses that may cause acoustic shadowing 2
• Limitations include restricted field of view and limited depth of penetration, which may affect visualization of large fibroids or those in an enlarged uterus 1

Transabdominal Ultrasound (TAUS)

• Complements TVUS, especially for significantly enlarged fibroid uterus or large subserosal/pedunculated fibroids that may be poorly visualized on TVUS 1
• Useful when TVUS has limitations due to poor acoustic penetration 1
• May be limited by poor acoustic windows from decompressed urinary bladder, retroverted uterus, large body habitus, or bowel gas 1

Doppler Ultrasound

• Should be considered a standard component of pelvic ultrasound examination 1
• Helps evaluate internal vascularity of fibroids and differentiate between vascular and nonvascular tissue 1
• Assists in distinguishing fibroids from other pelvic pathologies 1

Advanced Imaging Options

Saline Infusion Sonohysterography (SIS)

• Minimally invasive procedure that distends the endometrial cavity with saline 1
• Enables better delineation between endometrial pathologies and submucosal fibroids 1
• Shows good agreement (kappa 0.80) with diagnostic hysteroscopy for classifying submucosal fibroids 1
• Accurately depicts the percentage of intracavitary component of submucosal fibroids, which has treatment implications 1

MRI

• Superior to ultrasound for identifying and mapping fibroids 1
• May alter management in up to 28% of patients compared to ultrasound findings 1
• When clinically indicated, gadolinium-based IV contrast is preferred for identification of fibroid vascularity and other characteristics 1
• Provides excellent delineation of fibroid location, size, number, and can differentiate fibroids from adenomyosis and endometriosis 1
• Allows assessment of fibroid viability, uterine artery anatomy, and detection of ovarian arterial collateral supply to the uterus 1
• Particularly useful for complex cases with multiple fibroids or when planning for specific interventions 3

Ultrasound Elastography/Sonoelastography

• Measures tissue strain and can increase diagnostic accuracy in identifying myometrial pathologies 1
• Shows excellent agreement with MRI-based diagnosis of fibroids and adenomyosis 1
• On sonoelastography, fibroids appear as well-delineated dark areas due to stiffer/compressed smooth muscle fibers 1

Imaging Algorithm for Fibroids

1. Initial Evaluation: Pelvic ultrasound (combined TAUS and TVUS with Doppler) as first-line imaging 1
2. For submucosal fibroids or endometrial cavity involvement: Consider saline infusion sonohysterography (SIS) 1
3. For complex cases: Proceed to MRI with and without contrast when 1:
   • Multiple fibroids are present
   • Precise mapping is needed for surgical planning
   • Differentiation from adenomyosis or other pathologies is required
   • Evaluating for potential malignancy (though rare)
   • Planning for uterine-sparing procedures like uterine fibroid embolization

Common Pitfalls in Fibroid Imaging

• Misdiagnosis of adenomyosis, solid adnexal tumors, or endometrial polyps as fibroids 2
• Failure to differentiate between fibroids and leiomyosarcoma (extremely rare but critical distinction) 4, 2
• Inadequate assessment of submucosal fibroids that may affect fertility or cause abnormal uterine bleeding 1
• Incomplete evaluation of the entire uterus, particularly in cases of multiple fibroids 1
• Relying solely on TVUS for large fibroids or an enlarged uterus without complementary TAUS 1

By following this evidence-based imaging approach, clinicians can accurately diagnose fibroids, characterize their location and size, and develop appropriate treatment plans to address fibroid-related morbidity and improve quality of life.