a procedure to drain bile to relieve pressure in the bile ducts caused by a blockage. an x-ray of the liver and bile ducts locates the blockage of bile flow. images made by ultrasound guide placement of a stent (tube), which remains in the liver. bile drains through the stent into the small intestine or into a collection bag outside the body. this procedure may relieve jaundice before surgery. also called percutaneous transhepatic biliary drainage and percutaneous transhepatic cholangiodrainage.