The HIDA scan with CCK is the definitive test for gallbladder function.
Pressure and bloating can be symptoms of gallbladder disease. Other common symptoms can include, nausea, burping, diarrhea, pale bowel movements, stomach noise, pain under the right ribs, pain under the left ribs, generalized pain in the back, pain in the right shoulder, etc.
Generally the HIDA scan test does not hurt. However, when they inject CCK which causes your gallbladder to contract it can cause discomfort in some people. On the other hand the results should definitively tell your Dr. whether the gallbladder needs to come out.