When you have a colonoscopy, you have to eat a low fibre diet for a few days before hand, then fast for a day while drinking a solution of magic stuff that 'clears you out'. So yep, you have diarrhoea until there is nothing but water going straight through you.
A low fibre diet mainly consists of my less preferred foods, but only foods I really hate is bananas and ketchup so it was quite easy really.
We did have a little bit of trouble finding a low fibre bread - they all claim to be packed with fibre. I told my surgeon this later, he said that they are still all low fibre.
I'm not very good a skipping meals usually, so I was a bit worried about the fasting, but I managed it very well.
The first few sips of the bowel prep solution don't seem too bad - a bit like alka seltzer or something. By the time you're on your last dose, you're choking it down.