Gallbladder isn’t opaque to X-ray, but when particular radiopaque dyes are provided by either mouth or intravenousinjection they’re excreted by the liver from blood into bile and get to the gallbladder. In the gallbladder, the dye is concentrated and therefore the gallbladder becomes opaque to X-rays.
The ultrasonography is a noninvasive imaging technique to visualize the gallbladder and other elements of the biliary equipment. This technique has mostly replaced the cholecystography.
Endoscopic Retrograde Cholangio Pancreatography (ERCP)
In this technique, under direct vision via a fibreoptic endoscope, a catheter is inserted into the hepatopancreatic ampulla and radiopaque contrast medium is injected, and bile and pancreatic ducts are visualized.
The bile and pancreatic ducts can now also be visualized by the noninvasive magnetic resonance imaging (MRI) technique.