Today I spent over 90mins having x-rays taken of my kidneys. Its difficult to see the structure of kidneys in x-rays so a contrast medium is injected into you and you have to have an empty bladder.
Towards the end of the 90mins, before the final x-ray was taken, I was asked to 'go and empty my bladder again'; I replied I wasn't sure I could go - having been before the start.
Back came the chirpy response from the radiographer - 'Oh yes you can, there's quite a lot in there - I've just looked!' ;-)