Like I said, I had three hida scans and never vomited. I don't think that most people do, but if you have a weak stomach, I would think you would be more likely to do it. If you are have a fear of vomiting, however (I certainly don't like to do it!) then you probably have a very strong stomach and are in good control of it and won't vomit. My stepfather said some of the patient's response had to do with how the tech administered the drug. My stepfather always did it a little squirt every 30 seconds to a minute, to keep from overwhelming anybody. The first tech I had was not my stepfather and he gave it all at once and it made me feel sicker. But it doesn't last a real long time, that feeling. 5 minutes or so at the most from the time it starts to the time it tapers off. It doesn't come on you strong and all at once. The worst part of it was having to stay laying down. If I could have sat up and walked around, then it may not have bothered me at all. But bad gall bladders are notorious for making you feel worse when you lie flat on your back. Maybe someone will take that into account one day and make it where you can stand up against the wall and have the camera film you. All in all I think the test takes about 30 minutes and with the prep (gettting a line in, waiting for the radiodactive dye to settle) it takes 45 minutes to an hour. So of that you're uncomfortable about 5 minutes. Not bad, really. And if they find it is your gall bladder and they get it out, it makes it very worth your while. No more pain! And drugs to treat the bile! Definitely worth the tradeoff.
Fly, if you have a bad gall bladder and haven't vomited yet, you probably will. I did once or twice, and I was an exception to the rule. Most people who suffer from gall bladder disease for a while will end up vomiting more often than I did. Some people are even vomit-predominent (I was diarrhea-predominant). And it's worse than vomiting when you are sick with the flu or food poisioning because it's full of bile and that stuff burns so bad! Your esophagus and the back of your throat will feel scorched for a day or more and no amount of water or milk will help it. So better to risk the test and hopefully get a diagnosis than to keep a bad gall bladder and suffer. And if your gall bladder isn't the problem, then the test probably won't bother you.
I bet, Faerun, those beans did you in more than your chips. Those can do regular people in. Personally, I found that my flatulence dropped off significantly when I had my gall bladder problem. I would get gas-like cramps but couldn't burp or pass gas. Man the times I wished I could! It just felt hung up in there. But some people do get indigestion and belch a lot from it, so it's one of those variables.
If I were you, I would push for the test, because you really do sound like you have a problem. Since I had a couple of tests come back inconclusive/negative because I had them done when I wasn't having a problem, I would either 1, schedule the test when you're in a bad streak or 2, cause yourself to have a bad streak. A day or two before the test, just eat all of those things that bother you. The greasiest fish and chips you can find, cokes and beers and fizzy water, pizza with extra cheese--you name it. Get yourself torn up, then go in. Hopefully your gall bladder will show up as bad, you can have it out and you can go on with life. If it doesn't show up while you're in the midst of having intestinal fits, then you can just about rule out gall bladder disease and chalk it up to IBS. Either way you should know for certain what problem you have, so hopefully making yourself sick on purpose won't have been in vain.
If I knew 8 years ago what I know now, I would have made myself sick before having my first hida scan. Because I wasn't in the middle of an attack and it came back negative, I suffered needlessly for four more years. If I had it to do over again, I would not hesitate to make myself sick in the pursuit of getting the tests to come up positive. That's how bad it was for me over those next four years. I have cautioned other people about caffeine, fat, etc. and so many of them will say, "Oh, I can't live without my pot of coffee everyday." And without malice or sarcasam I tell them, "Well, then, you're just not that sick." Because if they were bad sick, they'd drop anything in the pursuit to be pain and diarrhea free. Me, I once was a 2-liter-a-day coke drinker. When I figured out that it was the caffeine making my gall bladder worse, I dropped caffeine like a hot potato. Gave up cokes, gave up tea, sometimes even avoided chocolate. I didn't miss those 2am attacks with diarrhea and horrible pain. I hurt bad enough to give up just about anything.
And on a final note, if this problem really is your gall bladder, it won't go away. You'll be okay for a while, then you'll be sick again. It will just keep happening and the length of time you stay sick will generally increase and it may manifest itself in new and unpleasant ways.