Choledochal Cyst

  • Etiology: due to ductal plate malformation or anomalous junction of pancreatic duct and distal CBD with reflux of pancreatic enzymes-> inflammation / weakening / stricture and dilation, is ductal ectasia rather than a true cyst resulting in congenital dilation of bile ducts
  • Todani classification
    — Type I involves common bile duct saccular dilation, diffuse or focal (80-90%)
    — Type II diverticulum of common bile duct
    — Type III choledochocele (intraduodenal diverticulum)
    — Type IVa+IVb – intra and extrahepatic dilation, extrahepatic sacular form
    — Type V Caroli disease – intrahepatic saccular and fuisform dilation, polycystic kidney disease, congenital hepatic fibrosis, portal vein abnormality and hyperplasia and hypertrophy of hepatic artery branches
  • US: cystic mass in the liver in the region of the porta hepatis that appears to communicate with the biliary tree, gallbladder is normal
  • HIDA scan: radiotracer uptake in the lesion, confirming its communication with the biliary tree
  • Complications: bile stasis, stones, biliary obstruction from stones and sludge, cholangitis, cyst can compress and cause intrahepatic ductal dilation, pancreatitis from abnormal pancreaticobiliary junction and external compression, malignancy (rhabdomyosarcoma in children, cholangiocarcinoma in adults)
  • Clinical: classic triad is pain / jaundice / RUQ mass although presentation varies with age
    — Infant – jaundice + acholic stool
    — Child – biliary obstruction, jaundice, RUQ mass – or – recurrent pancreatitis – or – pain
    — Adult – pain

Radiology Cases of Choledochal Cyst

CT and US of choledochal cyst
Axial CT with contrast of the abdomen (upper left) shows a large round low density structure inferior to the liver and separate from the gall bladder. Transverse and sagittal US of the liver show the round structure to be cystic and in communication with a dilated biliary tree. Delayed image (lower left) from a hepatobiliary scintigraphy exam shows concentration of radiotracer into the round structure which is slowly excreted into the bowel. AP image of an intraoperative cholangiogram (lower right) shows dilation of the intrahepatic and extrahepatic biliary tree with free flow of contrast into the bowel.
US and nuclear medicine scan of choledochal cyst
Sagittal US of the liver (left) shows a cystic mass in the liver that appeared to communicate with the biliary tree. Image from a hepatobiliary scan (right) shows radiotracer uptake in the lesion, confirming its communication with the biliary tree.
US of choledochal cyst
Transverse US of the liver shows a cystic lesion distinct from the gallbladder in the liver. Hepatobiliary imaging showed it communicating with the biliary tree.