The biliary tract starts at the hepatocyte canaliculi, which empty into biliary ductules. Larger ducts join the right and left hepatic ducts, which drain into the common hepatic duct (CHD) at the porta hepatis. When the cystic duct from the gallbladder joins the CHD, the common bile duct (CBD) is formed. The CBD is usually 8 cm long and 0.5 to 0.9 cm in diameter. It passes behind the first portion of the duodenum, through a groove in the head of the pancreas, and empties into the second portion of the duodenum at the ampulla of Vater. Distally the pancreatic duct may join the CBD before it also empties into the ampulla. The gallbladder, a pear-shaped distensible organ, 8-10 cm in size with a normal capacity of 30 to 50 mL, lies in a fossa on the visceral surface of the liver on a line separating the right and left hepatic lobes. When distended with acute inflammation, the fundus comes in close contact with the anterior abdominal wall in the right upper quadrant near the ninth and tenth costal cartilages, giving rise to the Murphy s sign. Posteriorly, it abuts the first and second portion of the duodenum and the hepatic flexure of the colon. Thus, extension of the inflammation of the gallbladder may lead to spontaneous fistulas into these hollow organs. Gallstone disease is a major health problem in the United States. It affects approximately 20% of adult Americans. Gallstones are formed by the precipitation of insoluble bile constituents: cholesterol, polymerized bilirubin, bile pigments, calcium salts, and proteins. Gallstones are classified into cholesterol, black pigment, and brown pigment stones. Cholesterol stones are most frequent in industrialized societies. Black pigment stones occur in patients with chronic hemolytic disorders, and brown pigment stones are associated with impaction in the biliary tract. These stones are more prevalent than cholesterol stones in the Far East. Cholesterol stones may be pure, large (>2.5 cm), solitary or mixed (>70% cholesterol), multiple, smooth, and faceted. Black and brown stones contain less than 25% cholesterol and are multiple and irregular. They contain polymerized bilirubin and calcium salts (bilirubinate, phosphate, and fatty acids). All types of gallstones may become calcified. The calcification is usually central in pigment stones and peripheral in cholesterol stones.