GALLBLADDER SCAN (NUCLEAR) - A test that uses a radioactive tracer to look for bile duct obstruction or gallbladder inflammation. A special tracer is injected into a vein that tends to collect primarily in the liver. It is then excreted in the bile where it makes its way to the gallbladder. A gamma camera measures the tracer (radioactivity) and generates an image of the gallbladder and biliary system.