would like to know
That's pretty common. Your gall bladder was probably used to a pretty high fat intake before WLS so was cranked up, working hard all the time to make all that lovely bile to break down those fats. All of a sudden you aren't eating the fats, so it has less to do, and it isn't too happy about that. So...being a bored little gall bladder, it either gets infected (cholecystitis) or makes and/or moves around stones (cholelithiasis). There....that's my $1.98 explanation from my days as a surgical floor nurse. I think it's somewhat accurate, but I'm not an expert.