"CT scan with the doctor's instructions not adhered to."

I recently attended the hospital for a CT scan. The instructions were for a CT scan with IV contrast. When I arrived I was given a container of white liquid to drink. I had consumed 2 cups of the fluid when it was taken away and I was told that would be enough. The scan was to look at my adrenal gland. I was then taken in for the scan. The operator told me after the scan that they didn't need to insert the cannula and I could go.

On returning home I thought about what had happened and found it unacceptable that the instructions by the doctor had not been adhered to. I am concerned that not having the instructions followed means the diagnosis could be incorrect. I look forward to hearing back from the hospital in this regard.