Diagnostic Ultrasound - Abdomen and Pelvis

Echogenic Bile
TERMINOLOGY
Synonyms
• Biliary sludge, tumefactive sludge, biliary sand, microlithiasis
Definitions
• Presence of particulate material (calcium
bilirubinate/phosphate or carbonate crystals with
cholesterol monohydrate crystals) in bile
○ Larger particles (1-3 mm) are microliths, which may
become nidus for gallstones
IMAGING
General Features
• Best diagnostic clue
○ Mobile, gravity-dependent nonshadowing echogenic
layer within gallbladder (GB); mid-/high-level echoes
○ Echogenic, mobile "mass" within GB
• Location
○ Within gallbladder
• Size
○ Variable
Ultrasonographic Findings
• Grayscale ultrasound
○ Echogenic bile
– Amorphous, mid-/high-level echoes within GB
– Floating punctate echoes; may show ring-down
artifact
– Sediment in dependent position
– Lack of posterior acoustic shadowing
– "Hepatization" of gallbladder: Sludge-filled GB with
same echotexture as liver
– Lack of internal vascularity
○ Tumefactive sludge
– Round, low to intermediate echogenicity mass-like
"lesion"
– No posterior acoustic shadowing
– Gravitates slowly to dependent position on changing
patient position
– Lack of intralesional vascularity on color Doppler
examination
□ Note that twinkling artifact may be mistaken for
color flow
• Power Doppler
○ No internal vascularity in "mass-like" GB lesions
CT Findings
• NECT
○ Medium-density material within GB
○ No wall thickening or pericholecystic inflammatory
change
• CECT
○ Lack of contrast enhancement
○ Intact GB wall without evidence of invasion in adjacent
structures
MR Findings
• T1WI
○ High signal dependent layer
• T2WI
○ Lower signal dependent layer
Nonvascular Interventions
• ERCP
○ Filling defects within gallbladder
○ Gravitate to dependent position
Imaging Recommendations
• Best imaging tool
○ Transabdominal ultrasound
• Protocol advice
○ Use highest frequency transducer possible for better
detail of intraluminal filling defect/echoes
○ Focal zone should be adjusted to level of gallbladder for
optimal resolution
○ Change patient position to demonstrate mobility of
intraluminal material to dependent portion
– Distinguish from side lobe artifacts by scanning from
different approaches
○ Interrogate areas of color flow with spectral Doppler to
confirm twinkling artifact
DIFFERENTIAL DIAGNOSIS
Cholelithiasis
• Formed echogenic material within GB
• Marked posterior acoustic shadowing
○ Occasionally GB stone may be nonshadowing
• Mobile and gravitate to dependent position
Focal Adenomyomatosis
• Polypoid lesion arising from, and attached to, wall of GB
• Most common at GB fundus
• Not mobile on changing patient position
• May show "comet tail" artifact
• Lack of internal vascularity
• Other features of adenomyomatosis in rest of GB
Gallbladder Polyp
• Small (usually < 1 cm), smooth, polypoidal mass fixed to GB
wall
• Smooth contour
• Single or multiple
• Usually avascular, occasionally with increased internal
vascularity
Gallbladder Empyema
• Low-level echoes within GB lumen due to presence of
pus/inflammatory exudate
• Distended GB
• Other features of acute cholecystitis
○ GB wall thickening, pericholecystic fluid collection,
positive sonographic Murphy sign, impacted stone
• Clinically septic with localized peritoneal signs in right upper
quadrant
Blood Clot
• Heterogeneous low-level echoes floating within GB, mobile
• Blood-fluid level within GB
• Retracting nonvascular clot; may conform to configuration
of GB
• History of trauma, instrumentation, GI bleed
• May be associated with hemorrhagic cholecystitis
Diagnoses: Biliary System
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