However, because CT uses x-rays and is expensive, it is not as widely used as ultrasound. A radiopaque substance is then injected into the ducts of the biliary tract, and x-rays are taken of the biliary tract. Percutaneous transhepatic cholangiography involves inserting a long needle through the skin and into the liver, then injecting a radiopaque substance into one of the liver's bile ducts. A doctor may use ultrasound for guidance when inserting the needle. The x-rays clearly reveal the biliary tract, particularly a blockage within the liver.
Operative cholangiography uses a radiopaque substance that is visible on x-rays.
During an operation, the substance is injected directly into the ducts of the biliary tract. X-rays then reveal clear images of the biliary tract. Simple x-rays can often reveal a calcified gallstone. Liver Biopsy A liver specimen can be obtained during exploratory surgery but is more often obtained by inserting a needle through the skin and into the liver. Before the procedure, the patient receives local anesthesia.