I think there is some confusion here, at least with a couple responses. Correct me if I'm wrong
jimmy1s269, but the OP isn't talking about analingus, instead it is talking about anal sex followed by a blow job. Two very different things.
It should also be said that porn performers typically do a fair bit of preparation before those kinds of scenes, clearing out the colon with enemas, etc. Even that doesn't make it particularly healthy, but that's not something that is even shown. Remember, porn is selling a fantasy.