oh my.. I am so sorry for your loss
When I volunteered for the cat rescue.. we saw alot of this.. but with 150 cats all running free in a large area, it was hard to tell when they got sick. We lost so many from liver problems.. the tell tale sign of the yellow skin, the jaundice.. we knew they would most likely not make it.. after vet bills and 24 hour care.. most of thetime they didn't pull through..
Again, so very sorry for your loss