
Oh I'm so bleeding for you. One of my girls, our second last home-bred probably had this but it was never confirmed because our then vet faffed around re a diagnosis. He insisted that scanning was enough and refused to x-ray. This began with repeated UTIs which did respond to treatment, but then returned. That vet, part of a big Practice said he had nothing more to offer at one stage, saying he'd send us up to Bristol for further investigation. At the time I not only spoke with my wonderful vet back up country (she said she'd have opened her up let alone x-ray) and took a second opinion of my sister's vet - ditto x-ray. When the needed x-ray was done by the senior partner of the original vet, her chest cavity was riddled with growths and by then her legs had swollen alarmingly, so given she was over 12, we opted to give her peace.
She was given pain killing meds, Metacam and then Tramadol which sent her loopy so she came off that fast. By the last day, I could see in her eyes she was pleading with me to let her go. Hardest thing, well one of, I'd had to do with my hounds and even sadder was this was the end of my line, leaving her brother distraught at being the only one left, apart from my hurting.
Just as with mine, you WILL know when life has become too hard to hear. Not that makes this terrible decision easier.