Hellbuff,
If you have pouchitis or SIBO the treatment would be the same, a course of antibiotics. Only a pouch scope would distinguish between the two, since the symptoms are pretty much the same.
The gallstone could be an incidental finding and unless you also have an inflamed gallbladder (cholecystitis) or and obstructed bile duct, there would not be any likely surgery needed. Possible, just not likely.
I have had a solitary gallstone for decades and also thought my gallbladder was toast. But, all my symptoms wound up being from chronic pouchitis. Antibiotics took care of that, but I could not get off of them. That was when my GI opted for Remicade and Imuran. I have been in remission ever since, maybe 8 years now.
There are a couple of reasons why we get gallbladder problems. First is the tendency toward dehydration (the same reason we are prone to kidney stones). The other reason is that UC is associated with liver and gallbladder disease.
Jan