I had day surgery when my DD1 was nearly 6 months old. I don't remember having to pump and dump. It's something you can discuss with the anaesthetist prior to admission, as there may be some drugs that are more appropriate when you're BFing. We had some frozen EBM, but I fed DD just prior to surgery and I think she had one smallish feed of EBM (we used a cup, not a bottle) while I was in surgery/recovery etc, and then I just fed her normally after that.

Good luck with the surgery - not pleasant to look forward to, but you'll be glad once it's behind you and hte problem is fixed