Diagnosis and treatment of benign and malignant tumors of the liver, biliary tract, pancreas and spleen; gallstone disease (gallbladder stones and intrahepatic and extrahepatic bile duct stones); congenital hepatobiliary and pancreatic diseases (such as congenital choledochal cysts); acute pancreatitis, acute and chronic cholecystitis, and cholangitis; and liver transplantation.