ERCP - Endoscopic retrograde cholangiopancreatography, or ERCP, is a diagnostic-therapeutic procedure that involves the x-ray of the pancreatic duct and biliary tree after the selective introduction of a contrast material into the common bile duct and pancreatic duct. In this procedure, a flexible endoscope is passed through the mouth and down into the duodenum. A catheter is then passed through the endoscope and inserted into the pancreatic and bile ducts. A contrast agent is injected into the catheter which highlights the coarse and caliber of the ducts. Narrowing, stones, or ductal tumors can be identified with this procedure.