The first examination is US of the right upper quadrant to evaluate the liver, GB, bile ducts, and the pancreas. If biliary obstruction is identified then CT of the pancreas is suggested to define the exact site and cause of obstruction. It may or may not be clear at this point whether biliary obstruction is related to choledocholithiasis. Cholelithiasis can exist without choledocholithiasis and choledocholithiasis can occur without cholelithiasis. If further imaging is required this is usually accomplished via ERCP with cholangiographic data being obtained during the examination. Many times the evaluation is completed at this point. MRI is reserved for complex entities such as cholangiocarcinoma or incompletely defined pancreatic neoplasms. During ERCP a biliary stent may be placed to relieve biliary dilatation, and the pancreatic duct can also be evaluated if pertinent.