Midlothian Girl, you may have seen Gallstones coated in bile that looked green - however if you knew enough about the subject we wouldn't be having this conversation. As for disputing my credentials (which I haven't in fact presented), which is a cheap trick, I have worked in a top hepatobiliary surgical unit and also worked for Professor Cuschieri for a short term as a house officer. Professor Cuschieri is, as you should know, one of the top minimal access surgeons in the world.