Endoscopic retrograde cholangiopancreatography (ERCP) is a diagnostic and interventional procedure technique using both endoscopy and fluoroscopy for examination and intervention of the biliary tree and pancreatic ducts. It is typically performed by doctors with endoscopic qualifications (e.g. general surgeons, gastroenterologists) rather than radiologists.
It involves passing an endoscope to the descending duodenum and subsequently cannulating the ampulla of Vater, after which contrast can be injected outlining the biliary tree and various procedures can be performed.
Regarding a purely diagnostic study, CT intravenous cholangiograms and MRCPs are becoming more popular, namely because the complication rate is far lower. Pneumobilia is common post-ERCP including when the history of the procedure is remote (especially if a sphincterotomy has been performed).