Actually I'm having surgery (fistulotomy) & a colonscopy tomorrow morning!
My CRS is having me drink "Fleet" saline solution. I took my first dose a few hours ago, and have been visiting the bathroom frequently; but I'm so happy to say that I have no cramping at all! That was a big concern for me too.
I realize you are supposed to take Mag Citrate. Now for me personally, that caused quite a bit of pain/cramping. (I was taking it for supplemental purposes at the time - so I didn't take much). I read later on that it can cause cramping/runs in some invidivuals.
I followed some advice I found here on the board & on another site - I ate a "low residue" diet for the past 5-6 days. Basically white bread, white potatoes, noodles, tuna, chicken, eggs, pudding; avoided all greens, nuts, legumes, fruit/veggie skins, and whole grains. I also avoided all tomato products, as well as citric acid.... a poster here said that will help avoid any "burning" associated with the runs. And - it's true.
I also bought good, soft TP and some A&D ointment.
This prep has been very tolerable for me. If you tend to get cramps easily (which I do!) you might want to ask your CRS about using Fleet instead.
This will be my first surgery & colonoscopy, and I'm pretty scared!! At least the prep hasn't been as awful as I feared
Good luck to you!!