I'm sorry, but if my vet suggested doing a biopsy of my pup's liver and kidneys I would leave and probably never use her again. I have used her since 2001 and she has never suggested doing something of this nature and trust me I have had some very, very sick pups. I think it is terrible that your vet is suggesting that you will pay more at a specialist. Like he is giving you a "deal".
One of YHR's foster moms took a pup to a vet who did the same thing only it was orthopedic stuff. He said the knees and hips all needed surgery and gave her a low quote for such surgery. We had her take the pup to the board certified surgeon that we use and he said she did not need ANY surgery!! This was a couple of years ago and she was adopted and is doing just fine!
I believe strongly from what you are saying that Bumble should be with a specialist. It concerns me greatly that your vet is doing this. Sounds like a money maker for him.