Diagnostic Ultrasound - Abdomen and Pelvis

Cholelithiasis
TERMINOLOGY
Synonyms
• Gallstone, cholecystolithiasis
IMAGING
General Features
• Best diagnostic clue
○ Ultrasound of gallbladder (GB)
– Highly reflective intraluminal structures
– Posterior acoustic shadowing
– Mobile on changing patient's position
• Size
○ Variable
• Morphology
○ Laminated and faceted
Ultrasonographic Findings
• Grayscale ultrasound
○ Highly reflective intraluminal structures
○ Prominent posterior acoustic clean shadow
○ Gravity dependent and mobile
○ False-negative ultrasound: Small contracted GB full of
stones, small gallstones, GB in ectopic/unusual position,
obese/uncooperative patient
○ Variant ultrasound features
– Collection of bright echoes with acoustic shadowing in
gall bladder fossa representing GB packed with
stones, may be mistaken for duodenal bulb
– Double-arc shadow sign or wall-echo-shadow (WES)
sign: 2 echogenic curvilinear lines separated by
sonolucent line (anterior GB wall, bile, curvilinear echo
from stone and then shadow)
– Nonshadowing gallstone (stone < 5 mm)
– Immobile adherent stone or nonmobile stones in GB
neck
○ Associated findings if superimposed complications
– Acute cholecystitis: Thick-walled and distended
gallbladder, positive sonographic Murphy sign,
pericholecystic fluid
– Acute cholangitis: Obstructing common bile duct
(CBD) stones, biliary dilatation
– Acute pancreatitis: Ill-defined swelling of pancreatic
parenchyma, inflammatory change in adjacent soft
tissue
– Biliary fistula/gallstone ileus
• Color Doppler
○ Twinkling artifact should not be mistaken for flow in GB
mass; evaluate with spectral Doppler
○ Increased flow in pericholecystic region in cholelithiasis
complicated by acute cholecystitis
Radiographic Findings
• Radiography
○ Radiopaque in 10-20%
– Pigmented stone: 50% radiopaque
– Cholesterol stone: 5% radiopaque
CT Findings
• NECT
○ Calcified gallstones are hyperdense to bile
○ Pure cholesterol stones are hypodense; inverse
relationship between cholesterol content and CT
attenuation
– May be isodense to bile and will be missed by CT
○ Stones may contain nitrogen gas centrally: "Mercedes-
Benz" sign
MR Findings
• T2WI
○ Small focus of signal void or low signal outlined by
markedly hyperintense bile within gallbladder
• MRCP
○ Round foci of signal void inside gallbladder
Nonvascular Interventions
• ERCP
○ Mobile filling defects inside contrast-filled gallbladder
○ ± stones in extrahepatic bile ducts
Nuclear Medicine Findings
• Hepatobiliary scintigraphy
○ Not sensitive for gallstones
○ Used for diagnosis of acute or chronic cholecystitis
– Nonfilling of gallbladder or decreased ejection
fraction, respectively
Imaging Recommendations
• Best imaging tool
○ Ultrasound
• Protocol advice
○ Transabdominal ultrasound
– Patients should fast for 6-8 hours
– Examine patient in supine and left decubitus/oblique
position to demonstrate mobility of gallstone,
consider erect or semiprone positions
□ In supine position, stones are highly likely to be
found in GB neck with gravitation to fundus in left
decubitus position
– Optimize parameters to maximize visualization of
posterior acoustic shadowing from small stones
– Always evaluate for biliary dilatation and signs of
cholecystitis, cholangitis, or pancreatitis
DIFFERENTIAL DIAGNOSIS
Gallbladder Polyp
• Small, round nodule with smooth contour arising from
gallbladder wall
• Low/medium echogenicity, usually multiple, no posterior
acoustic shadowing
• Not mobile, may have short stalk or may be sessile
Gallbladder Sludge
• Sludge may aggregate into a mass or may layer
• Low/medium echogenicity; mobile
• Lack of posterior acoustic shadowing
Gallbladder Carcinoma
• Well- or poorly defined mass from gallbladder wall;
nonmobile
• Infiltrates adjacent liver parenchyma, associated
lymphadenopathy
• Increased vascularity within lesion on color Doppler
Diagnoses: Biliary System
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