Diagnostic Ultrasound - Abdomen and Pelvis

Biliary Ductal Dilatation
IMAGING
General Features
• Best diagnostic clue
○ Tubular anechoic fluid-filled structures accompanying
portal veins in extrahepatic and intrahepatic segments
• Location
○ Intrahepatic and extrahepatic bile ducts
Ultrasonographic Findings
• Grayscale ultrasound
○ Intrahepatic ductal dilatation
– Ductal diameter > 2 mm
– Tubular anechoic branching structures accompanying
portal veins
□ "Parallel channel" sign
□ Earliest intrahepatic ducts to dilate are often in left
hepatic lobe
– Dilated ducts may be irregular and tortuous
– Central stellate confluence of tubular structures
proximally at liver hilum
○ Extrahepatic ductal dilatation
– Diameter of common bile duct > 6-7 mm or more than
40% of diameter of adjacent portal vein
– Anechoic tubular structure parallel to main portal vein
and perpendicular to hepatic artery in porta hepatis
– Can trace its communication with intrahepatic ducts
• Color Doppler
○ Helpful to distinguish dilated ducts (no color flow) from
adjacent vascular branches of hepatic arteries and portal
veins
CT Findings
• Near water attenuating tubular structures within liver
parenchyma adjacent to intrahepatic portal veins
• Intrahepatic ducts communicate with near water
attenuating tubular structure between the liver and
duodenum
MR Findings
• T2 hyperintense tubular structures within liver parenchyma
• Intrahepatic ducts communicate with T2 hyperintense
tubular structure between liver and duodenum
Imaging Recommendations
• Best imaging tool
○ Transabdominal US useful as initial investigative tool for
assessment of degree, extent, and cause of biliary
obstruction
○ Transabdominal US may help guide interventional
procedures
○ For better anatomical evaluation of underlying
pathology, CT or MR provides supplemental information
• Protocol advice
○ US scanning technique
– Include comprehensive assessment on sagittal,
transverse, and oblique planes, intercostal and
subcostal approach
– Intrahepatic ducts are better visualized on deep
inspiration
– Semierect right posterior oblique (RPO) or right lateral
decubitus position helps minimize obscuration by
overlying bowel gas
– Harmonic imaging allows better visualization of
dilated duct and its content
DIFFERENTIAL DIAGNOSIS
Portal Vein Cavernoma
• Cavernous transformation of portal vein; racemose
conglomerate of collateral veins
• Color Doppler will show portal venous flow
Thrombosed Portal Vein Branch
• Hypoechoic (acute) or echogenic (chronic) filling defect
within main portal vein and its branches
• Color Doppler: Patchy flow or complete absence of flow
Venovenous Collaterals
• Collateral between thrombosed/stenosed hepatic veins
and normal hepatic veins/portal veins
• Color Doppler: Venous flow
• Seen in Budd-Chiari syndrome
Peribiliary Cysts
• Small cysts along biliary triads
Choledochal Cyst
• Congenital cystic dilatation of biliary tree
PATHOLOGY
General Features
• Etiology
○ Nonobstructive causes
– Advanced age
– Previous cholecystectomy
– Congenital disease (e.g., choledochal cyst)
– Hepatic artery stenosis in liver transplant recipients
○ Obstructive causes
– Intrahepatic: Calculus, sclerosing/AIDS cholangitis,
recurrent pyogenic cholangitis, ascending cholangitis,
cholangiocarcinoma, trauma, etc.
– Extrahepatic: Common duct calculus, pancreatic head
adenocarcinoma, cholangiocarcinoma, lymph node
compression, stricture, ampullary stenosis etc.
CLINICAL ISSUES
Presentation
• Depends on underlying cause (e.g., acute cholangitis: Right
upper quadrant pain, fever and chills)
• Obstructive jaundice: Painless or right upper quadrant pain
SELECTED REFERENCES
1. Holm AN et al: What should be done with a dilated bile duct? Curr
Gastroenterol Rep. 12(2):150-6, 2010
2. Rubens DJ. Ultrasound imaging of the biliary tract. Ultrasound Clinics.
2(3):391-413, 2007
3. Gandolfi L et al: The role of ultrasound in biliary and pancreatic diseases. Eur
J Ultrasound. 16(3):141-59, 2003
4. von Herbay A et al: Color doppler sonography avoids misinterpretation of
the "parallel channel sign" in the sonographic diagnosis of cholestasis. J Clin
Ultrasound. 27(8):426-32, 1999
Diagnoses: Biliary System
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