Diagnostic Ultrasound - Abdomen and Pelvis

Choledochal Cyst
TERMINOLOGY
Synonyms
• Choledochal malformation, biliary cyst,choledochocele
Definitions
• Congenital segmental dilatation of intrahepatic &/or
extrahepatic bile ducts
IMAGING
General Features
• Best diagnostic clue
○ Nonobstructive, disproportional balloon-like dilatation of
biliary tree
• Location
○ Involve extrahepatic ducts (more common), intrahepatic
ducts, or both
• Size
○ Varies from 2-15 cm
• Morphology
○ Todani classification: Modified in 2003
– Type I: Solitary cystic fusiform dilatation of common
duct (CD) (50-85%)
□ Ia: Cystic dilatation of entire CD; associated with
anomalous pancreatobiliary ductal union (APBDU)
□ Ib: Focal dilatation of entire CD; not associated with
APBDU
□ Ic: Fusiform dilatation of entire CD; associated with
APBDU
□ Mild dilatation of intrahepatic duct blurs distinction
with type IVa
– Type II: True diverticulum of supraduodenal CD (2%)
– Type III: Choledochocele; dilatation limited to
intraduodenal part of CD (1-5%)
□ IIIa: Cystic dilatation of intraduodenal CD
□ IIIb: Diverticulum of intraduodenal CD
– Type IV: Presence of multiple cysts (15-35%)
□ IVa: Involvement of both intrahepatic and
extrahepatic ducts
□ IVb: Multiple extrahepatic cysts without
intrahepatic cysts
– Type V: Single or multiple intrahepatic cysts (multiple
intrahepatic cysts known as Caroli disease)
Ultrasonographic Findings
• Grayscale ultrasound
○ Best 1st test to demonstrate dilated biliary tree and
extent of ductal involvement
○ Antenatal ultrasound (25 weeks): Right-sided cyst in fetal
abdomen ± dilated hepatic ducts
○ Uncomplicated choledochal cyst
– Cystic extrahepatic mass separate from gallbladder
and communicating with common hepatic or
intrahepatic ducts
– Fusiform dilatation of extrahepatic bile duct
– Abrupt change of caliber at junction of dilated
segment to normal ducts
– Intrahepatic ductal dilatation due to simultaneous
involvement or secondary to stenosis
• Color Doppler
○ Useful for demonstrating position and displacement of
adjacent vessels
CT Findings
• CECT
○ Cystic lesions contiguous with biliary tree
○ Multiplanar MIP images are ideal
○ Type V (Caroli disease): "Central dot" sign (enhancing
portal vein radicles indenting cystic spaces)
MR Findings
• MRCP
○ Has replaced percutaneous cholangiogram in
preoperative planning
○ Helpful to evaluate pancreatobiliary junction anatomy
Nuclear Medicine Findings
• Hepatobiliary scintigraphy
○ Large photopenic area in liver, showing late filling and
prolonged stasis of isotope
○ Prominent intrahepatic ductal tracer activity
○ May be confused with other causes of biliary obstruction
Other Modality Findings
• ERCP and percutaneous cholangiogram
○ Usually reserved for difficult or complex cases
○ Best depiction of all types of choledochal cysts
○ Helpful to evaluate pancreatobiliary junction
Imaging Recommendations
• Best imaging tool
○ MRCP; ERCP if endoscopic intervention is being
considered
DIFFERENTIAL DIAGNOSIS
Biliary Obstruction of Various Causes
• Proportional (rather than fusiform) dilatation
• Degree of dilatation less than choledochal cyst
• Primary lesion identifiable (e.g.,
choledocholithiasis,pancreatic ductal, ampullary, or distal
common bile duct [CBD] cancer)
Pancreatic Pseudocyst
• No communication with bile ducts
• CECT: Enhancement of fibrous capsule
• MRCP: Hyperintense cyst contiguous with dilated
pancreatic duct
• ERCP: Pseudocyst communicating with pancreatic duct
seen in 70% of cases
Primary Sclerosing Cholangitis
• Idiopathic inflammatory process leading to progressive
fibrosis and strictures of intra- and extrahepatic bile ducts
• Multifocal areas of alternating biliary strictures and
dilatation
• Abnormal bile duct wall thickening and enhancement
Recurrent Pyogenic Cholangitis
• Dilatation of both intra- and extrahepatic bile ducts
• Cast-like biliary stones, sludge, pneumobilia, and abscess
• MRCP: Ductal rigidity and straightening, rapid tapering of
peripheral intrahepatic duct
• More common in Asians
Diagnoses: Biliary System
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