What do gallbladder polyps with internal vascularity suggest?

Gallbladder Polyps with Internal Vascularity: Clinical Significance and Management

While gallbladder polyps with internal vascularity are more often seen with neoplastic polyps, vascularity alone is not an independent risk factor for malignancy and should not influence risk stratification according to the Society of Radiologists in Ultrasound (SRU) consensus guidelines. 1

Relationship Between Vascularity and Polyp Type

• Detectable vascularity, typically at the polyp base, is more commonly observed in neoplastic polyps compared to non-neoplastic polyps 1
• However, larger cholesterol polyps (benign, non-neoplastic) may also demonstrate internal vascularity on color Doppler imaging 1
• The SRU consensus conference committee explicitly states that detection of polyp vascularity should not influence risk stratification 1

Vascular Patterns and Their Significance

• Different vascular patterns may help differentiate polyp types when using contrast-enhanced ultrasound (CEUS):
  • Stalk-like central enhancement pattern may indicate a cholesterol polyp (benign) 1, 2
  • Intralesional straight vessels are associated with adenomatous polyps 1
  • Intralesional branching vessels correlate with malignant neoplasms and may indicate internal perfusion defects 1

Technical Considerations in Detecting Vascularity

• Advances in sonographic technology have increased sensitivity for detecting subtle vascularity in polyps that were previously below detection threshold 1
• Novel modified power Doppler-based techniques operate at very low velocity scales using advanced clutter suppression:
  • Superb Microvascular Imaging (SMI, Canon Medical Systems) 1
  • MicroFlow Imaging (MFI, Philips Healthcare) 1
  • Microvascular flow imaging (MV-Flow, Samsung Medison) 1
• These techniques can separate slow or small-vessel flow signals from clutter artifacts, displaying flow information at high spatial resolution 1

Contrast-Enhanced Ultrasound (CEUS) Findings

• CEUS offers advantages in characterizing gallbladder polyps due to high spatial and temporal resolution 1
• CEUS can help distinguish vascular lesions from sludge 1
• Enhancement patterns on CEUS may help differentiate polyp types:
  • Non-neoplastic lesions: late microbubble enhancement that is hypoenhancing compared to liver 1
  • Neoplastic lesions: marked early enhancement 1
  • Adenomatous polyps: eccentric hyperenhancement and sustained homogeneous enhancement 1
  • Malignant polyps: wash-out pattern 1

Risk Factors for Neoplastic Polyps

• Polyp size >1.15 cm is an independent predictor of adenoma 3
• Intralesional blood flow is an independent predictor of adenoma 3
• Lack of cholecystitis is associated with adenoma 3
• Single polyps are more commonly associated with malignancy, but this finding is not consistent across all studies 1

Management Recommendations

• The SRU consensus guidelines recommend risk stratification based primarily on polyp morphology and size, not vascularity 1, 4
• For challenging cases where differentiation between tumefactive sludge and other gallbladder lesions is difficult:
  • Short-interval follow-up US within 1-2 months with optimized technique is recommended 1, 5
  • CEUS may be used for further characterization if available 5
  • MRI may be considered if CEUS is not available 5
• CT has inferior diagnostic accuracy compared to CEUS or MRI for characterizing gallbladder lesions 5

Clinical Pitfalls and Caveats

• Vascularity alone should not trigger more aggressive management 1
• Even small polyps (<10 mm) have potential to be neoplastic and become malignant, as demonstrated in case reports of malignant transformation 6
• Malignant transformation of adenomas may occur over a relatively short time period 3
• The current guidelines recommend cholecystectomy for GB polyps ≥10 mm in size and for smaller polyps (6-9 mm) with risk factors such as age >50, sessile morphology, or symptoms 7, 8