basic steps required to perform diagnostic percutaneous transhepatic cholangiography
Under fluoroscopic guidance, a 21 G or 22 G needle is passed into the liver through an inferior intercostal or subcostal space at the level of the right midaxillary line. It is important to verify that the needle does not pass through the pleural space. The needle is withdrawn during injection of contrast material in an effort to opacify a bile duct that may have been traversed as a result of the needle pass. When a bile duct is identified, injection of contrast material is continued, and the biliary tree is opacified. A diagnostic cholangiogram is performed with spot fluoroscopic images obtained in anteroposterior and multiple bilateral oblique projections. Ultrasonography (US) may also be used to guide access into the biliary tree, and is especially useful when accessing the left bile ducts.