Not to revive an old thread, but I'm starting my pre-op diet with nothing but Optimum Nutrition Gold Standard Protein shakes and they're great with Water and skim milk.
120 calories w/ water, or 200 calories w/ skim milk.
24g of protein w/ water, or 32g grams of protein w/ skim milk (depending on who you believe for protein grams in 8 oz of skim).
1 gram of carbs per serving.
I have tasted the vanilla ice cream and rocky road and they're both pretty good.
Get it frmo Amazon it's fairly inexpensive at 50-60 cents per ounce.