Can i get easy to understand explanation of "hida scan" procedure, in the medical field?

Hepatobiliary study: Patient injected intravenously with isotope tagged to chemical hida that is extracted preferentially by liver cells mimicking bile.Some stored in gall bladder and some enters small bowel from common bile duct. Cholecystokinin, natural hormone, slowly injected intravenously to stimulate gall bladder contraction. Normal function has at least 35% emptying of gall bladder in adults. Some pts have pain.