CT scan IV drug

[Fantasian]

After having a CT scan today SWIM had quite a strange experience. An IV injection was given to him presumeably to act as an indicator to allow the scanner to work. The nurse said beforehand "Now when this goes in you will feel a warm sensation and then you will feel like you've wet yourself! but dont worry you havnt it's just the drug." Sure enough when the fluid entered Swim's arm he felt a mild warm sensation nothing like the morphine rushes he'd experienced in the past but something all the same. (nothing pleasurable i might add) Then he felt exactly what the nurse described a wet warm feeling imbetween his legs (note he is fully clothed) and he immidiately had the feeling that he had passed diohriah(sp). After the scan was over he checked himself out and sure enough nothing was there to his relief.

Im curious what drug has this effect? And why does it have this effect?

Note: the nurse mentioned something about iodine but i didnt want to question her too thouroughly as to appear a bit odd.