Did he eat no fat for the first 3-4 weeks? If not, then he needs to go on that diet and see if his body can regulate itself/ If he did then and still has this, then yes, use whatever medication the doctor recommended.
I don't know who or what "under" is so I don't fully understand your reply. However, you should eat a very low or no fat diet for the first 2-3 weeks at least after removal. They leave a bile duct to do the work of the gallbladder and it needs time to slowly come
"online", so to speak, and function properly. FOrcing it to work by eating fat before it is ready to wrok properly can cause it to malfunction and not do its job. Sometimes, going back and eating no fat for a while can straighten it out but maybe not. He may just have to use the medicine from now on. There are several ways to do it and the one his doctor prescribed is but one.
I was told to always watch my intake on fats and oils. That post surgery I would always have problems with those items. Fast food is guaranteed to give me problems these days. Mine has been out 10 years. I'm sure the instruction has changed a bit since then. Best wishes to both of you.
No-one told me to adhere to any sort of special diet (Heck, my sister had a hamburger 3 days after her surgery and to this day is fine). I had mine out a little under 2 months ago; did low fat for the first month because of research I did online - I can eat anything just fine.