Kiwi's bile acid numbers were higher than yours, so we went ahead and drove to a pet nuclear medicine place where they did a scintography scan on her to see if she had a shunt. (She didn't!
) As far as I know, the scintography is the only for sure way to tell if there is a shunt or not (aside from surgery). I don't think ultrasounds can rule out a shunt 100% and $500 is a lot to spend for something that doesn't give you a for sure answer.
Since your numbers are so low, it doesn't seem like a shunt is possible. It could be that your baby has MVD/HMD (but probably pretty mild)? In that case, I think it is probably safe to do the spay and while they are there, to do a liver biopsy to see how the liver is doing. But I would defintely talk to the vet about that and she how she/he feels about that. Only you can really decide if you are comfortable putting your baby through surgery right now. Good luck!