They can't do an MRI with a bullet in them. It would tear the guts apart. It was explained in a previous thread by some brave father with a daugher in an accident. There is a point where they can do so much in an operation then have to back off temporarilly because of life signs and body pressure.
I know a basketball player that played for Pitt in the last few years that has a bullet in his head. They don't want to mess with it because it is too close to some vitals. I mean, this is touchy stuff when you mess with the vitals in the body. I understand now, there are some things better off just left alone.