Percutaneous transhepatic cholangiography (PTHC or PTC) is a iagnostic test used to visualize the anatomy of the biliary tract. A contrast medium is injected into a bile duct in the liver, after which X-rays are taken. It has various purposes, such as the visualisation of the biliary tree in cases where endoscopic retrograde cholangiopancreatography (ERCP) has been unsuccessful. Initially reported in 1937, the procedure became popular after a 1952 report in the English-language literature. If the biliary system is obstructed, PTC may be used to drain bile until a permanent solution for the obstruction is performed (e.g. surgery). Advancement of the percutaneous cannula through the biliary tract to the duodenum may aid in visualising the ampulla of Vater during further attempts at ERCP.