Anja
I'm not an expert on this, but I don't think the oil actually gets into the gall bladder - it stays in the bowel, but the body recognizes that it needs to digest that big load of fat and so the gallbladder is supposed to contract and start squirting bile - it's the squirting thing that triggers the stone release and pushes stuff through the ducts. I think the liver actually produces the bile for digestion fats, and the gallbladder is sort of a bile reserve tank. I've got to study up on that. It might help you to look at an anatomy book of the liver/gallbladder and find out where that stone is that your doctor is talking about. There are probably a lot more than he has found (i.e. in the liver). I've kicked out tons of pre-calcified cholesterol stones and I don't even fit the profile, nor have I had over gallbladder symptoms, I just knew my liver/GB were congested.
If I were you , I'd try everything I could to save my gallbladder before considering surgery. I'd do a lot of stone dissolving products like Julia Chang's Gold Coin Grass, the Coptis at night to increase bile flow, some brand of phosphoric acid like Phosfood, and also apple juice or malic acid (unless you have problems with ulcers - the acid bothers some people). I take malic acid powder in cranberry juice a few days before flushing, but you could do it longer. (I can't do all the apple juice because of candida.) The castor oil pack is a good idea too, but I think you have to do them a lot - like every night for a month to really get the benefits from it. Do you have a naturopath that you can consult with? One other idea is something called "visceral manipulation" to manually untwist the organs. Some bodyworkers are trained in that, and I actually saw a doctor who did some of that on me - it was actually very gentle, more a craniosacral-style technique. I think that would also help it's function - being in the proper position.
Have you done a flush at all yet? About six years ago after a greasy dim sum meal I had what I KNOW was a gallbladder attack and went to the hospital. This was before I knew anything about flushing, although I'd heard of it. They couldn't find anything on ultrasound and X-ray, and I went to a holistic doc the next day who said he knew about the flush and that it could be effective, but the only problem was that if the gallbladder was really inflamed in an acute situation, it could burst when you tried to flush. I don't know if that's really true in an otherwise "healty" person, or if he was trying to protect himself, not advising the flush. I've been reading these boards almost daily for over a year, and have never read anything about a gallbladder bursting during a flush.
Anyway, don't give up yet.