<<Disclaimer: Verify this information before applying it to your situation.>>
Just to add my two bits worth. I had a CT scan last November
following an apparently ruptured liver cyst, found in an ultrasound
after a severe bout of abdo pain, but not found 6 weeks later. I had
no reaction to the contrast medium except a metalic taste in the mouth
which was expected.
I live in Australia, the contrast may be different.
Jim