I still don't understand, what does taking bupe have to do with your bile duct?
I would find a new doctor personally. If they think its because its binding you up, there are 100 other things you can try. Stool softeners, laxative (dont take for long), diet, or simply live off nutribullets for a week until you are shitting water.
Bupe does bind me up more than any other opiate as I mentioned, unlikely that flake of a doc would know, though.
I still say you are wrong regarding the opiates, though

Bupe is an opiate. So how is bupe working? It would be physically impossible unless bupe has bound to your receptors forever. (not possible). In which case you have a 1 of a kind bupe. Half life = 20 years.
Jacking up your tolerance? Yes. Hanging onto the receptor for some weeks? Yes. Forever...impossible. When I came off it, withdrawaled for some days. Took some methadone and didn't feel shit. Took about a week and finally felt something. Unfortunately a massive dose of narcan came a week later so have really yet to stabilize. It does do something strange to you for sure. Wonder if thats the secret behind those implants. Drip an antagonist into this guy for some time. And even when it comes out you won't feel anything for a bit.
In any case, you have plenty subs. No need to torture yourself for no reason.