I understand where you come from, My dog Spot passed away 2 years back because of liver failure. He had a swollen gut, would not eat but would drink loads and loads of water and would hide in a part of the garden where he would spend the whole day laying there.

The vet did request if we wanted to put Spot to sleep as he was already 9 years old, but we refused as we believed Spot could come out of it.

He stayed with the vet which did their best to help Spot but he passed away one evening in the Vet's clinic.

I regretted not being beside Spot during his last few days. Being alone in the vet's cage as he passed away still makes me feel guilty. If I could have done any different... I'd choose for me to take him home when the vets told me I could... at least then Spot could pass away with his family around him.