Physical Danger
It's easy to see the danger that your patients will be in, but you? You're the one who treats and operates on them. One could even say that...you are the danger? To kidney disease at least.
You're sort of like the feds, trying to keep the Al Capones and Heisenbergs off the streets of a patient's innards.
As for danger to you, coming into contact with people's inner fluids is always a risk, and not just for you squeamish types. However, there are practices in place that keep medical work safe; you just have to make sure to follow them.
Physical complications from stress are a legitimate fear here. It's a very tough job, with very long hours. Sort of a life-consumer. So watch out for that―make sure to keep in shape, draw a line between work and life, and relax once in a while. Although hey, you'll have gone to medical school, what are we doing telling you how to take care of yourself?