I had a hida scan today, and the second part caused me pain. why?

Ask the doc: Hida scan done to check for biliary obstruction (including in gallbladder). Generally not painful, but trying to pass gallstones is. Call your doc.

Mimics gb symptoms: Patient is injected intravenously with isotope that selectively is extracted by liver cells mimicking bile. Some of this is stored in gall bladder and some enters small bowel from common bile duct. Cholecystokinin is a natural hormone slowly injected intravenously to stimulate gall bladder contraction. Some patients do get nausea and pain and decreased gb contraction consistent with gb disease.