FYI: I had a bad gallbladder for 3 years (and lived on a low fat diet to avoid surgery as long as I could). HIDA scan never picked up my problem, but it did eventually have to come out. MRCP was the only test that showed any issue at all, and was still debateable enough result that no one could decide for sure if it needed to come out (until it did get acute and need to come out).
But do NOT LET THEM removed your gallbladder unless you're sure it must be removed. It isn't a useless organ. Some people live ok without it, but others have lifelong problems. My digestion has never been the same. I have more reflux without it. Having no GB can cause bile reflux since there's no where to store concentrated bile anymore. I struggle with weight (extra 20-30 lbs) and never ever had a weight problem before. It changes your digestive system, do not be fooled into believing it's normal to live without it.
So be educated and be SURE before it comes out... please