Never heard of a hydro scan. Did you mean HIDA Scan? If so, here is info about it......
A HIDA scan is an imaging procedure that helps track the production and flow of bile from your liver to your small intestine. Bile is a fluid produced by your liver that helps your digestive system break down fats in the foods you eat.
A HIDA scan, which stands for hepatobiliary iminodiacetic acid scan, creates pictures of your liver, gallbladder, bile ducts and small intestine. Cholescintigraphy, hepatobiliary scintigraphy and hepatobiliary scan are alternative names for HIDA scan.
A HIDA scan is a type of imaging study called a nuclear medicine scan. This means the HIDA scan uses a radioactive chemical, or tracer, that helps highlight certain organs on the scan.
The test is called a HIDA scan and shows the function of the gallbladder.