Diagnostic Ultrasound - Abdomen and Pelvis

Gallbladder Cholesterol Polyp
TERMINOLOGY
Synonyms
• Focal gallbladder (GB) cholesterosis, polypoid cholesterosis
Definitions
• Abnormal deposit of cholesterol ester producing villous-like
structure covered with single layer of epithelium and
attached via delicate stalk
IMAGING
General Features
• Best diagnostic clue
○ Multiple, small, nonshadowing lesions attached to
gallbladder wall
• Location
○ Anywhere on GB wall
○ Most commonly in middle 1/3 of gallbladder
• Size
○ Usually 2-10 mm
• Morphology
○ Well-circumscribed, ovoid/round in configuration
Ultrasonographic Findings
• Grayscale ultrasound
○ Polypoidal mass arising from GB wall
– Small, usually in range of 2-10 mm
– Single or multiple
– Medium- to high-level internal echoes
– Smooth in contour, sometimes multilobulated outline
– Round or ovoid shape, narrow base with gallbladder
wall
– Does not cast posterior acoustic shadow (vs.
gallstone)
– Not mobile on changing position (vs. biliary sludge)
– Overlying GB wall is intact & normal
– No invasion of adjacent liver parenchyma or regional
nodal metastases
○ Variant US appearances
– Large size: Lesions up to 20 mm have been described
□ Fine pattern of echogenic foci, best seen with
endoscopic ultrasound
– Pedunculated with well-defined stalk from GB wall
• Power Doppler
○ Avascular or hypovascular on Doppler examination
○ Larger lesions may have slight internal vascularity
CT Findings
• NECT
○ Small, soft tissue density nodule on GB wall
○ Intact GB wall
○ No calcification or fat component
• CECT
○ Mild enhancement
○ Multiplicity usually better assessed after IV contrast
administration
MR Findings
• T1WI
○ Small, round nodule in GB wall
○ Homogeneous, intermediate signal intensity
• T2WI
○ Homogeneous, intermediate to low signal intensity
• T1WI C+ FS
○ Mild enhancement with normal wall
• MRCP
○ Low signal intensity filling defect attached to GB wall
○ Contrast with markedly hyperintense bile within GB
lumen
Imaging Recommendations
• Best imaging tool
○ Transabdominal US is most sensitive technique for
detecting small cholesterol polyps
– Endoscopic ultrasound may supplement
transabdominal US
• Protocol advice
○ Adequate fasting prior to US is essential for optimal
study
○ Optimize resolution and set focal zone to level of GB
mass to improve accuracy of mass characterization
○ Scan in supine, decubitus (left > right lateral) positions to
demonstrate immobility of GB polyp
○ Management algorithm for incidental polypoid GB mass
– < 6 mm: No follow-up
– 7-9 mm: Yearly US follow-up to monitor size
– > 10 mm: Surgical consult
○ Further evaluation with CECT or enhanced MR for
atypical features or proceed to surgery
DIFFERENTIAL DIAGNOSIS
Hyperplastic Cholecystosis/Adenomyomatosis
• Focal (fundal) form
○ Smooth, sessile mass in fundal region or mid body
"waisting"
○ "Comet tail" artifacts from GB wall
Nonshadowing Cholelithiasis
• Highly echogenic
• Mobile and gravity dependent
• Note: Up to 20% of resected polyps represent stones stuck
to gallbladder wall
Adenoma
• 4% of gallbladder polypoidal masses
• Solitary lesion
• Larger size (> 10 mm) but variable
• Usually pedunculated
• Color flow may be present; improved sensitivity using
endoscopic ultrasound
Biliary Sludge
• Medium- to high-level echogenicity
• Mobile and gravity dependent
• Fluid sediment level
• No posterior acoustic shadowing
Inflammatory Polyp
• 5-10% of gallbladder polyps
• Multiple in 50% of cases
• Background of gallstone disease and chronic cholecystitis
Diagnoses: Biliary System
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