So sorry to be so long responding. But I'm afraid I can't be of much help except in that I always prefer the natural path if there's any way to do it.
It does seem to me, since it is an enzyme problem that something natural could do the trick, but I have no idea what to suggest as this is a new one for me.
I hope someone who visits and knows something to help Malinda will post some good herbs for her to try.
Surely an herb health professional could tell you some good things to try. I know my sister kept their dog, who had been diagnosed with cancer, alive for many years passed what the vet had predicted, and it was because of some very good natural things they kept her on.
So I hope you will look into it further before going the route of the shunt. And I do wish I could have been of more help to you.