An endoscopic retrograde cholangiopancreatogram (ERCP) lets a doctor look at the tubes (ducts) that drain the liver, gallbladder, and pancreas. To do this, the doctor uses a thin, flexible, lighted scope (endoscope). He or she puts the endoscope into the mouth and gently moves it down the throat and into the esophagus, stomach, and duodenum (where the stomach connects with the small intestine). The doctor slowly guides the scope until it reaches the place where the ducts from the pancreas (pancreatic ducts) and gallbladder (bile ducts) drain into the duodenum. The doctor can put very small tools through the endoscope. The tools allow him or her to take tissue samples, add in contrast (dye), or open a narrowed bile duct.