Biliary Tree Pathology

Pathology of the Biliary Tree

• The liver's origin of bile marks the biliary tree's proximal start.
• The common bile duct's segment nearest the pancreatic head is the tree's most distal part.
• Biliary dilatation normally happens proximal to any obstruction.
• Extrahepatic structures of the biliary tree are the common bile duct, cystic duct, and the common hepatic duct's fraction.
• Intrahepatic structures of the biliary tree consist of all other regions.

Dilated Intrahepatic Ducts

• It is important to differentiate between dilated intrahepatic bile ducts and portal veins.
• The "Parallel channel sign" or "Shotgun sign" describes a dilated common duct relative to the size of the adjacent portal vein.
• Bile ducts increase in size as they approach the porta hepatis.
• Biliary ducts exhibit more tortuosity compared to accompanying portal veins.
• Bile ducts branch in a "star-shaped" design, marking a stellate confluence.
• Bile structures attenuate sound less than blood, producing posterior acoustic enhancement which is acoustic enhancement.
• Color Doppler helps differentiate by not filling bile ducts while delineating the portal vein.

Biliary Obstruction

• The distal common bile duct is the most common location for obstruction.
• In the majority of cases, extrahepatic ducts will dilate first.
• Choledocholithiasis stands out as the primary cause of common bile duct obstruction.
• Other causes of common bile duct obstruction include chronic pancreatitis, acute pancreatitis, and pancreatic carcinoma.
• Jaundice is often a sign of biliary obstruction.

Cholangitis

• Cholangitis is the inflammation of the biliary ducts.
• The bile duct walls thickness is greater than 5 mm.
• Symptoms include right upper quadrant (RUQ) pain, fever, and jaundice.
• Sonographic findings consist of varying degrees of biliary dilatation, biliary sludge, and bile duct wall thickening.

Pneumobilia

• Pneumobilia is characterized by air within the biliary tree.
• Recent biliary or gastric surgery, emphysematous or prolonged acute cholecystitis may cause pneumobilia.
• Sonographically, it manifests as echogenic linear foci with a posterior ring-down artifact within the ducts.

Choledocholithiasis

• The presence of stones inside the ductal system is known as Choledocholithiasis.
• In most cases the CBD stones have migrated from the gallbladder.
• Common duct stones are commonly usual sequelae of calculous cholecystitis.
• Stones are likely to affect Vater's ampulla and may project into the duodenum.

Mirizzi Syndrome

• An impacted stone in the cystic duct causes extrahepatic biliary obstruction through mechanical compression of the common hepatic duct.
• Jaundice, pain, and fever are clinical signs.
• Associated findings include intrahepatic duct dilatation, cystic duct stone, and curved segmental stenosis of the common hepatic duct (CHD).

Choledochal Cysts

• Pancreatic juices refluxing into the bile duct because of irregular pancreatic duct junction into the distal common bile duct causes Choledochal Cysts.
• This results in duct wall abnormality, weakness, and outpouching of the ductal walls.

Clinical Findings of Choledochal Cysts

• Usually occur to children under the age of 10 years old.
• Jaundice and duct dilatation are common symptoms.
• Older patients are at high risk of developing ductal carcinoma.
• High incidence of stone development occurs in the affected ducts.
• There can be five different types.