Hi Ithis is a long post I'm sorry but I just wanted to share my experience as it's not been what a expected. I'm on usc pathway and had sigmoidoscopy failed colonoscopy and now ct colon. 
I had gastrographin which just gave me stomach cramps felt a bit sick with a sore head. No bowel movements! 
I wasn't able to get the Iv buscopan due to heart arrynthmia so the inflation with 4litres of c02 was really not a nice experience. It was very painful and really not the best. Especially when I had to raise arms above my head and put them behind me. I tried to breathe and think about something else but this was very hard to do. 
when I had to move into my stomach that was so painful and I had to say to the radiologist  - give me time please to try and move as I'm so sore. I kept thinking oh my god I've had kids I can do this just get on with it and I knew I had to carry on and get through it . but it was really bad at some points. ..the feeling of bad cramping being stretch up with arms and trying to hold breath when they asked was so hard. 

The time when  Iv contrast  went in I was lying on my back I felt like my body was sinking and like I'd wet myself I had high pitch ringing in my ears and felt like I was going to be sick. I actually thought I was going to nearly pass out. I did not expect that feeling at all. 
the radiologist was speaking through the loudspeaker but I couldn't hear them properly so no idea what they said at that point. Just when I thought it was all done as I was waiting ages on table I was away into ct machine again for what seemed like ages. 

So I got myself home and spent past 2 nights being in stomach cramps, nausea, headache, itchy skin and explosive diarrohea water! I am now on antihistamines and I have steroids if it gets worse. As GP said reaction to IV Contrast. 

Has anyone experienced anything like this ? I feeling quite low today as it's felt like weeks of bowel prep and my life spent in the toilet!

sorry this feels like a rant