Us gallbladder: contracted w/ mild thickening of wall. all labs r normal except ast/alt(2-3 increase). no pain, is hida scan really necessary?

Basically YES.: there is both a compelling need to remove the gallbladder possibly and no evidence of a problem. Mostly, it is because the fine gallstones are running through a NON_WORKING gallbladder and irritating it and the liver. HIDA shows.... Without an exam, I can only give general information. cannot say in your particular case, but generally, this is how to proceed.