Back in the 30's the famous cartoon character Bugs Bunny coined the expression, "What's up, doc?" It had nothing to do with medical degrees, but was more a casual sort of bravado, when Elmer Fudd was about to shoot him. The expression caught on, and is used in all sorts of situations. I agree that "What's up, dude?" is the same.
Best wishes, - A.
Edit. Sorry, GG, I didn't see your post.