I'm kind of late to the game here, you've probably already taken care of it but what the hell: What about making a donation in his name to a charitable organization, Cancer or something like that, maybe the hospital he works in? A couple of times the doctors I worked for received gifts like that.
Doctors are tough to buy for unless you can ask a friend or family member what they're into. I wanted to get my sports med guy something and ended up asking his wife what he was into (she works in his office). Shocked the hell out of me when she said "He loves chocolate" (another non drinker/non smoker, very fit, I never would have guessed him to be a chocoholic).
That's another thought, really high quality food gifts are usually safe bet, too. If nothing else, they can put them out for guests. Think smoked salmon, organic, grass fed, dry aged steaks, extremely high quality chocolate, caviar, you get the drift.