What does internal vascularity in a gallbladder (GB) polyp suggest?

Internal Vascularity in Gallbladder Polyps: Clinical Significance

While detectable vascularity is more commonly observed in neoplastic gallbladder polyps compared to non-neoplastic polyps, the Society of Radiologists in Ultrasound (SRU) consensus guidelines explicitly state that detection of polyp vascularity should not influence risk stratification for malignancy. 1, 2

Relationship Between Vascularity and Polyp Types

• Detectable vascularity, typically at the polyp base, is more often seen with neoplastic polyps, but it is not an independent risk factor for malignancy 1
• Larger cholesterol polyps (benign, non-neoplastic) may also demonstrate internal vascularity on color Doppler imaging 1, 2
• Advances in sonographic technology have increased sensitivity for detecting subtle vascularity in polyps that were previously below detection threshold 1, 2

Vascular Patterns and Their Significance

• Different vascular patterns may help differentiate polyp types when using contrast-enhanced ultrasound (CEUS) 2:
  • Stalk-like central enhancement pattern indicates a cholesterol polyp (benign) 2, 3
  • Intralesional straight vessels are associated with adenomatous polyps 2
  • Intralesional branching vessels correlate with malignant neoplasms 2
• In a retrospective study, intralesional blood flow was identified as an independent predictor of adenoma on multivariate analysis 4

Technical Considerations in Detecting Vascularity

• Novel modified power Doppler-based techniques can separate slow or small-vessel flow signals from clutter artifacts 1:
  • Superb Microvascular Imaging (SMI, Canon Medical Systems) 1, 2
  • MicroFlow Imaging (MFI, Philips Healthcare) 1, 2
  • Microvascular flow imaging (MV-Flow, Samsung Medison) 1, 2
• These techniques display flow information at high spatial resolution and frame rate 1

Contrast-Enhanced Ultrasound (CEUS) Applications

• CEUS offers advantages in characterizing gallbladder polyps due to high spatial and temporal resolution 1, 2
• CEUS can help distinguish vascular lesions from sludge 1
• Enhancement patterns on CEUS may help differentiate between:
  • Tumefactive sludge (no enhancement) 1
  • Malignant neoplasms (early peripheral and sustained enhancement) 1
  • Benign lesions (tend to show washout) 1

Risk Stratification and Management Recommendations

• The SRU consensus conference committee explicitly states that detection of polyp vascularity should not influence risk stratification 1
• Risk stratification should be based primarily on:
  • Polyp size (≥15 mm warrants surgical consultation) 5
  • Growth rate (≥4 mm within 12 months) 5
  • Patient risk factors (e.g., primary sclerosing cholangitis) 5, 6
• For challenging cases, short-interval follow-up US within 1-2 months with optimized technique is recommended 1
• CEUS may be used for further characterization if available; MRI may be considered if CEUS is not available 1

Pitfalls and Caveats

• Vascularity alone should not determine management decisions, as many benign polyps also demonstrate vascularity 1, 2
• Polyp echogenicity, like vascularity, should not influence risk stratification 1
• Small polyps (<10 mm) with vascularity still have a low risk of malignancy, but should be monitored according to established protocols 5, 7
• Even small polyps have malignant potential, with rare cases of malignant transformation of polyps <6 mm reported 7, 8