Gallbladder Anatomy and Functions

Gallbladder/Biliary System

• The gallbladder is divided into three parts: neck, body, and fundus.
• Heister's valve controls bile flow in the cystic duct.
• Ultrasound evaluation of the gallbladder includes the liver, pancreas, gallbladder, and common bile duct (CBD).
• Portal vein and hepatic artery flow toward the liver; bile duct flow is away from the liver.
• The cystic duct connects the gallbladder to the bile ducts.
• The cystic duct and common hepatic duct merge to form the common bile duct. The CBD carries bile from the liver to the duodenum.
• The CBD and the main pancreatic duct (Wirsung's duct) join and enter the duodenum at the ampulla of Vater.
• The sphincter of Oddi is a muscular valve that relaxes to allow bile and pancreatic enzymes into the duodenum.
• Three types of gallbladder folds: Hartman's pouch (neck), Phrygian cap (fundus), and junctional (between the body and infundibulum).
• Cholecystectomy is gallbladder removal. Post-removal, the CBD size may increase (dilate).
• Patient positioning during scans is important for gallbladder and gallstone mobility assessment (ensuring no stones are lodged).
• Gallbladder size (less than 5 cm AP) and wall thickness (less than 3 mm) are key considerations.
• CBD measurement is typically performed where the right hepatic artery crosses between the portal vein and the bile duct.
• Normal CBD diameter is typically 5-6 mm or less.
• CBD diameter generally increases by 1mm per decade after age 60.

Gallbladder Disease

• Hydrops/mucocele is a round, distended, non-inflamed gallbladder due to cystic duct obstruction (finding).
• Murphy's sign indicates right-sided costal margin tenderness (gallbladder disease sign).
• Dilated intrahepatic ducts can present as: double barrel shotgun, parallel channel, stallate confluence, or too many tubes appearance.
• Cholecystokinin (a fatty hormone) can stimulate gallbladder contraction.
• The 5 Fs related to gallbladder disease are Fat, Forty, Female, Fair, and Fertile.
• Possible causes of gallbladder wall thickening (12 possible) include cholecystitis, adenomyomatosis, cancer, AIDS, cholangitis, cholangiopathy.
• Gallbladder sludge is non-shadowing, echogenic material of calcium bilirubinate and cholesterol crystals.
• Cholecystitis is characterized by gallbladder inflammation.
• Cholecystitis symptoms include: right upper quadrant (RUQ) pain, Murphy's sign, possible fever, increased white blood cell (WBC) count, and diffuse gallbladder wall thickening.
• Amylase elevation may suggest obstruction at the ampulla of Vater.
• Empyema involves purulent material (pus) within the gallbladder due to bacteria.
• Gallstones are known as cholelithiasis, and are echogenic, mobile, and shadowing.
• WES (Wall, Echo, Shadow) sign is gallstone-filled gallbladder. Other names for this include double arc or full of stones.
• Pneumobilia is gas in the biliary tree.
• Strawberry gallbladder is cholesterolosis.
• Gallbladder carcinoma has a high mortality rate (near 100%).
• 80-90% of gallbladder carcinoma cases also involve gallstones. Sonographic gallbladder carcinoma appearances include: focal wall thickening, intraluminal mass, or complete replacement by mass.

Biliary Tract Issues

• Biliary atresia is the absence of the extrahepatic biliary tree. It is suspected in jaundiced infants.
• Cholangitis involves biliary duct inflammation usually due to infection from the intestines.
• Cholangitis symptoms: fever, jaundice, right upper quadrant (RUQ) pain.
• Mirizzi syndrome is extrahepatic biliary obstruction caused by impacted stones in the cystic duct that cause mechanical compression to the common hepatic duct.
• Klatskin (cholangiocarcinoma) is a tumor at the common hepatic duct bifurcation (causing intrahepatic but not extrahepatic dilation).
• Gallstones and pancreatic head cancer are two primary causes for biliary obstruction.
• Serum alkaline phosphatase, GGT, and conjugated bilirubin are typically elevated in biliary obstruction.
• Choledocolithiasis is stones in the common bile duct (CBD). It is a leading cause of extrahepatic obstructive jaundice.
• Choledochal cysts are rare and result from bile duct wall weakness (causing cystic dilatation both intra and extra-hepatic).
• The sonographic appearance of choledochal cysts involves two cystic structures in the RUQ (GB and dilated intrahepatic duct).
• Choledochal cysts are common in Asian populations.
• Pancreatic adenocarcinoma is a malignant neoplasm (most frequent cause) that obstructs the biliary tree.