Ok, if this is what I had (mine was called a lower GI scan/series) then it was pretty uncomfortable (not to scare you). It wasn't so much painful as just really uncomfortable. Pretty sure they used Gastrograffin for mine as well (though I've heard barium is often used). There was no prep for mine (just no eating or drinking for like 8-12 hours or something). Just go in and the technician preps you. You lay on your left side and they insert the enema. The doc came in and explained to me that it would be uncomfortable, but he would stop whenever I asked him to if I could no longer tolerate it. It was kind of neat because I could watch the x-ray as he was filling up my bowel. It got more uncomfortable near the end when I felt super bloated, so I started to cramp really bad. They sometimes have to rotate you around on the x-ray table to get the liquid to go through the bowels, so at one point it was almost like I was standing up, ha! Afterwards I could no long hold the liquid in and I ended up releasing it all over the table, which was extremely embarassing, but I'm sure that happens pretty frequently. They then allow you to go to the bathroom to get rid of all the extra stuff and the exam is done. I think it probably took 30 minutes total to complete the exam. I felt extremely light-headed and almost fainted afterwards. I think it was because I hadn't eaten anything and I was probably dehydrated too. In my opinion this was the "worst" exam I had to go through, but nothing I couldn't handle. On the other hand, I pretty much have no shame after enduring that one, haha. Good luck to you!