I had to get mine out because it was only working at 31%, I literally sat there and writhed in pain all day unless I ate nothing but fruit or jello, because everything else had at least a little fat in it (usually at least 0.5 grams) and that was enough to make my gall bladder spazz on end for maybe 5 hours straight. I can't imagine how bad it hurts for you, being down to 21%!!
The surgery wasn't too bad, but boy was my stomach sore afterwards. It hurt to breathe (since it pulls on your abdominal muscles) for 2 weeks, and it hurt to do pretty much everything else for 5 weeks. As bad as that sounds, the miserable soreness for so many weeks after the surgery was nowhere near as bad as the awful stabbing pain every day for months before it. I'm glad I had it done.
The other surgical alternative you have is for them to try and dialiate the inflamed duct that is reducing your gall bladder function, but then they might rip or puncture something else in the process. If that were to happen they'd have to remove your gall bladder anyways and then try to repair the damage that was caused to other structures during the surgery. So, basically, unless your surgeon is really confident about being able to dialate you back to normal, when you're at the point of needing surgery to reduce the pain, just getting your gall bladder removed entirely is the most effective choice.