When I had a colonoscopy 5 years ago, I was a little backed up and quite sick. It was so hard to get the entire go lightly down. It took me all night and I never went quite clear. I was in the hospital with an IV in my arm and it was horrible. Many times I didn't make it to the toilet and was just mortified. I thought, what if I had been an elderly person? I was then able to get a small glimpse of how they must feel when treated this way, cause you know they are. I am glad I sent my hubby home so he didnt' have to witness all that. I think being impacted is worse than having diarrhea and having to do the prep.
Last January, I took half lightly and I started early in the day. It wasn't impossible to get down. They said I was squeaky clean and they even went into my small intestines a little bit. It was not a nightmare like the first time.
I have heard there is a miralax prep. You mix it with a clear drink. I will ask for that next time!!
Good luck with your prep.