Why is the CT colonography prep so damn dangerous?

I have to have a CT Colonography to make sure my IBS isn’t something else, but after reading everything I have to take and the potential dangers of death I’m thinking maybe sticking with IBS diagnosis isn’t so bad and I“ll just cross my fingers!

Why is it so dangerous.
Everything says – life threatening side effects.
Could cause death, blah blah – do not take if you think you have IBD – isn’t that why you do a colonography to see?!

Has anyone taken it before… I’m really thinking of pulling out and I’ve got to start taking everything tomorrow!

What are your thoughts?