My only problem with contrast is the sheer quantity they expect you to ingest.  When I went in and ended up having my appendix removed, they brought that shit out in a liter pitcher and basically wanted me to chug it as quickly as possible to get my scan done quickly.  That is just a ton of anything to drink, especially if you are already in severe abdominal pain.  I don't know, is that the normal amount required?  At the time I was 16, maybe 5' 6" 120 lbs.