I just spoke with a lady from the rescue who said Gus had his surgery today and the he came through it OK
She added that it will be a few days before he's completely out of the woods and that they did some sort of test to see if it's the kind of shunt that can be remedied. Apparently there are two different kinds? Anyway, she's the lady that transported him on Sunday and she reports that he's a little love bug full of kisses!
Keep praying for Baby Gus to make a full recovery.