All I can suggest is a second opinion...is there a vet school near you anywhere(or maybe not too far?)

All I can think of is the raw diet I have heard of...try a few tiny pieces of raw beef (like stewing beef, even).

You are doing everything you can. I kind of wonder about internal bleeding or blockage. With all the other tests - have x-rays been done?

HUGS! I hope someone here can relate to what is happening.

Many PT prayers going out to Lilly!