Diagnostic Ultrasound - Abdomen and Pelvis

Choledocholithiasis
TERMINOLOGY
Abbreviations
• Cholangiolithiasis, hepatolithiasis, biliary calculi, common
bile duct (CBD) stones
Definitions
• Choledocholithiasis: Extrahepatic ductal stones/calculi
• Hepatolithiasis: Intrahepatic stones/calculi
IMAGING
General Features
• Best diagnostic clue
○ Echogenic focus within bile duct, casting posterior
acoustic shadowing
• Location
○ Intrahepatic and extrahepatic bile ducts
– More common in CBD
• Size
○ Variable
• Morphology
○ Classified into 2 main types based on origin
– Primary choledocholithiasis: De novo formation within
bile duct
□ Calculi are composed predominantly of bilirubin (>
90% calcium bilirubinate composition)
□ Brown pigment stones are associated with bacterial
infections
– Secondary choledocholithiasis (more common):
Gallstone migration from gallbladder to bile ducts
□ Calculi are composed primarily of cholesterol
Ultrasonographic Findings
• Grayscale ultrasound
○ Appearance depends on site, size, and composition of
stones
○ Extrahepatic biliary stones
– Most commonly seen within CBD
□ Most often within lumen of periampullary
region/distal portion of CBD
– Classic appearance: Rounded echogenic lesion with
posterior acoustic shadowing
– Can be associated with extrahepatic and intrahepatic
ductal dilatation
○ Intrahepatic biliary stones
– Majority appear as highly echogenic foci with
posterior acoustic shadowing
– Located in region of portal triads paralleling course of
intrahepatic portal veins
– Small (< 5 mm) or soft pigmented stones may not
produce posterior shadowing
– Larger stone may cause biliary obstruction with focal
intrahepatic ductal dilatation
– Duct is filled with stones, appears as linear echogenic
structure with posterior acoustic shadowing
○ 10% stones: No posterior acoustic shadow
– Small size, soft, and porous composition
○ CBD/intrahepatic bile duct dilatation (IHBD) based on
stone size, degree, and duration of obstruction
○ Transabdominal US sensitivity for choledocholithiasis
reported between 20% and 78%, may be obscured
distally by bowel gas
○ Endoscopic US sensitivity for choledocholithiasis
reported between 94% and 98%
• Color Doppler
○ Echogenic focus is avascular, may show "twinkling"
artifact
○ Aids definition of dilated biliary ducts against
background intrahepatic parenchymal vessels
Radiographic Findings
• ERCP
○ Radiolucent filling defects within intrahepatic ±
extrahepatic bile ducts
○ Potentially therapeutic: Portal for stone retrieval,
sphincterotomy, or internal stent insertion
○ Sensitivity for choledocholithiasis reported between 90-
95%, considered "gold standard"
• Intraoperative and postoperative (T tube) cholangiography
○ Direct test for detection of CBD stones
○ Meniscus of contrast material clearly outlines margins of
stones
CT Findings
• NECT
○ Attenuation of calculi varies from less than water
density, through soft tissue, to dense calcification
– Typically high-density filling defect within biliary duct
○ Abrupt termination of CBD by obstructing stone
○ CBD &/or IHBD dilatation
– Varies depending on stone size, degree, and duration
of obstruction
○ Sensitivity for choledocholithiasis between 67-88%
MR Findings
• MRCP
○ Bile: T2 hyperintense signal
○ Ductal stones: T2 hypointense foci
○ Calculi manifest as low intensity filling defects within
increased signal intensity bile ducts
○ Sensitivity for choledocholithiasis between 81-100%
Imaging Recommendations
• Best imaging tool
○ US, MRCP
• Protocol advice
○ CBD stones are most commonly located in region of
ampulla of Vater
– High chance of being obscured by bowel gas
○ Practical advice to optimize detection
– Examine patient in different positions: Supine, left
lateral oblique, sitting upright
– Use firm probe pressure to collapse superficial bowel
and its content
– Perform detailed assessment of head region of
pancreas
○ Postcholecystectomy patients with persistent RUQ pain
– Image after fasting and 45 min to 1 hr after fatty meal
○ If gas obscures CBD; have patient drink 6-12 oz of water
– Keep patient in right decubitus position for 2-3
minutes and rescan in semierect position
Diagnoses: Biliary System
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