A flex sig examines the lower half of the colon and isn't as in depth as a colonoscopy. They insert a camera up through your anus and into your rectum. In order view the colon more closely, they send jets of air into the colon, which is where the cramping comes in. The procedure itself is very very brief compared to all the prep you must endure.My prep consisted of nothing but a clear liquid diet beginning at 5:00 pm the day before the procedure. At 7:00 pm, I was instructed to start drinking a bottle of magnesium citrate. At 9:45 pm, it kicked in, and I spent the next 6 1/2 hours in and out of the bathroom. At midnight, I was instructed to eat or drink nothing. This included no gum-chewing, toothbrushing (except for rinsing and spitting), etc. At 4 am, I was able to get 2 hours of sleep before having to give myself my first enema 2 hours prior to my departure to the hospital. I administered another enema 1 hour prior to departure. I arrived at the hospital 1 hour prior to the scheduled time of my procedure. Indeed, the preparation is far worse than the procedure. Ashley