Hardened crystal deposits formed from bile pigments, cholesterol, and calcium salts found in the bile duct (choledocholithiasis) or gallbladder (cholecystolithiasis). Commonly called gallstones, they are characterized by severe right upper quadrant abdominal pain or epigastric pain due to transient obstruction of the biliary tract. Other symptoms include nausea, vomiting, hyperbilirubinemia, and elevated alkaline phosphatase and gamma-glutamyl transpeptidase.