Gallbladder and Biliary Tree Part 2
Part 2 review of the gallbladder and biliary tree for radiology board exams. Download the free study guide on this episode by clicking here.
Show Notes/Study Guide:
What are classic imaging findings of primary sclerosing cholangitis?
With primary sclerosing cholangitis, multiple stenotic areas involving the intrahepatic and extrahepatic biliary tree are classically seen with associated areas of ductal irregularity and development of a cirrhotic liver with classic central regenerative hypertrophy. The classic mechanism is chronic cholestasis with subsequent inflammation/cholangitis and subsequent fibrosis of the biliary ducts. The etiology of the cholestasis is frequently idiopathic. Given cholestasis clinical symptoms include jaundice and pruritis. Treatment often requires eventual liver transplantation, and in a minority of unfortunate cases, primary sclerosing cholangitis can recur following liver transplantation.
True or false? Primary sclerosing cholangitis increases the risk of cholangiocarcinoma.
True. The association of primary sclerosing cholangitis with cholangiocarcinoma is commonly tested on board exams so make sure and commit this to memory.
True or false? Inflammatory bowel disease is associated with development of primary sclerosing cholangitis.
True. This is another classic association to remember for board exams as it is also commonly tested.
What are key features of primary biliary cirrhosis?
Unlike primary sclerosing cholangitis which causes areas of intra- and extrahepatic biliary stricturing, primary biliary cirrhosis manifests with irregular dilatation of the intrahepatic biliary tree with normal extrahepatic biliary ducts. Primary biliary cirrhosis is classically seen in middle-aged women and is of autoimmune etiology. Remember AMA serum positivity can be detected in many cases, and treatment can include ursodeoxycholic acid.
True or false? Primary biliary cirrhosis is classically associated with an increased risk of cholangiocarcinoma.
False. The classic association to remember for board exams with primary biliary cirrhosis is hepatocellular carcinoma. For board exams, remember that primary sclerosing cholangitis has an increased risk of cholangiocarcinoma (both have “cholangi” in the name) and primary biliary cirrhosis has an increased risk of hepatocellular carcinoma (as with most other types of cirrhosis).
True or false? A plastic stent is preferred for palliation of biliary obstruction secondary to incurable malignancy.
False. A metallic stent is often preferred for biliary obstruction secondary to incurable malignancy for palliative purposes due to superior patency rates compared to plastic stents.
How can one differentiate between gallbladder adenomyomatosis and gallbladder wall cholesterolosis?
While gallbladder adenomyomatosis and cholesterolosis can both show comet tail artifact, focal or diffuse gallbladder wall thickening can be seen with adenomyomatosis but not cholesterolosis. Classic features to remember with gallbladder adenomyomatosis include so-called Rokitansky Aschoff sinsuses which are intramural diverticula that fill internally with cholesterol crystals which can have diffuse or more focal involvement.
True or false? A cholesterol polyp of the gallbladder is not actually a polyp.
True. Cholesterol polyps of the gallbladder are a misnomer in that these are not actually polyps but rather enlarged papillary fronds containing lipid-laden macrophages attached to the gallbladder wall by a stalk. These do not show doppler flow and are typically small. A cholesterol polyp is the most common gallbladder polypoid lesion. Classic imaging findings on ultrasound include a non-shadowing, non-mobile polyp near the gallbladder wall which may show a thin stalk connecting to the gallbladder wall.
Are shadowing and/or mobility present on ultrasound for the following: gallstones, biliary sludge, and gallbladder polyps?
Gallstone: Shadows and shows mobility.
Biliary sludge: Does not shadow but is mobile.
Gallbladder polyp: Does not shadow and is not mobile.
What are classic features of Caroli’s disease?
Caroli’s disease is related to autosomal recessive congenital dilatation of bile ducts forming choledochal cysts. For Caroli’s disease, this is typically related to large and saccular intrahepatic ducts which by Todani classification of choledochal cysts is Type 5. Classic imaging features include large, saccular dilatation of intrahepatic ducts with the so-called central dot sign which results from the enhancing portal vein with associated blood flow centrally with surrounding biliary ductal dilatation. Caroli’s disease can lead to cholangitis, biliary stone formation, cirrhosis and cholangiocarcinoma. Caroli’s disease is associated with hepatic fibrosis, polycystic kidney disease (often autosomal recessive) and often presents in a pediatric or young adult patient.
Caroli’s disease is Todani Type 5 with intrahepatic biliary ductal dilation/choledochal cysts only. What is the Todani classification if both intrahepatic and extrahepatic choledochal cysts are seen?
Todani Type 4 choledochal cyst which includes both intrahepatic and extrahepatic biliary ductal dilation.
What is a so-called phyringian cap?
A phyringian cap describes the appearance of the gallbladder fundus folding in on itself and is generally important to recognize so as not to confuse with pathology and otherwise has no clinical significance.
What are key differences between pneumobilia and portal venous gas?
Pneumobilia and portal venous gas can both demonstrate a branching pattern of air. Pneumobilia is the accumulation of air within the biliary system and is classically seen as branching gas centrally within the biliary ducts near the hepatic hilum. One can remember this physiologically as flow in the biliary tree of bile moves towards the hilum which has been proposed to be the mechanism whereby air gets pushed centrally towards the hepatic hilum as well as anti-dependently in the left hepatic lobe. In contrast, portal venous gas typically accumulates in peripheral portal vein branches and one can remember this as normal portal venous flow is from the hilum towards the periphery of the liver which may push portal venous air peripherally. Portal venous gas classically results from ischemic bowel whereas pneumobilia has many causes including recent biliary procedures, sphincter of Oddi disruption including from recent passage of a gallstone, presence of a biliary-enteric fistula, or occasionally from biliary infections.
What is Mirizzi’s syndrome?
Mirizzi’s syndrome happens when a stone in the cystic duct or gallbladder neck causes obstruction of the nearby common bile duct via extrinsic compression. The resultant biliary duct dilatation can mimic more severe problems such as cholangiocarcinoma. Mirizzi syndrome is more likely to occur when there is an abnormally low insertion of the cystic duct within the common bile duct, or alternatively when increased tortuosity of the common bile duct is present. A classic clinical history for board exams would be a patient with recurrent jaundice and cholangitis.
A few final words on rare gallbladder variants: Know that an entirely intrahepatic gallbladder is rare but possible. Also note that gallbladder duplication is also rare but possible. A so-called duct of Luschka is also rare and is an accessory cystic duct which is one consideration to keep in mind in the setting of a persistent bile leak following cholecystectomy.