Wow. I'm sobbing.
My 18-year-old cat that I had from the age of 3 was getting up to the point where my mom was going to have to decide (I was away from home in college). One morning, right around my graduation, he had a seizure. My sister was home from school with my mom. Tiggy couldn't get up, so they took him in and sat with him while it happened.
I begged my parents to put a gerbil of mine to sleep when I was about 14. He had begun to eat his skin on his stomach and then his organs. My dad wanted to do it some other way, but I begged them to take him to the vet. They did.
Last spring, my wonderful baby Sammy came to tell us. Sammy was a semi-feral cat whom we took in at 4-m-o. He had lived behind a bar, been named by the regulars, and been fed who knows what. He was the only one of maybe 20 ferals there that would let people pet him just a little (we also took his sister who ended up being a snuggler once caught, though still skittish). Anyway, we kept his name and had a heck of a time finding the "right" home for him and Wicky. People don't usually want to wait for a cat to warm up to them. Shortly after I got Sadie, I noticed Sammy was losing some weight. Thinking that he was probably scared of Sadie and eating less to avoid being near her, I moved their food and kept watching him. His weight had fluctuated before, so I wasn't too concerned, just watchful.
One day, we were sitting on our couch talking about something and Sammy came up behind us and sat right between us on the back of the couch. He normally didn't get that close with more than one person around (actually, he normally only got that close to me; he loved being pet at 2am when I'd wake up to go to the bathroom... he'd hurry back and jump on the bed ahead of me, making me stand to pet him for a while before I got in bed). I knew something was up with just that. I looked at him and he was breathing hard with his mouth open and he had this look. I can't explain it. A cry for help, I think.
We rushed him to the vet with his sister. He was down to 5 pounds from 7 (he was a very small cat). They ran some tests but couldn't tell that anything was going on. They decided to take some xrays and sent us home. They had me pay a deposit; it was a new vet who didn't know us (we use that vet for all of our fosters). I remember paying and he was in the backroom behind held by this tech. He had to hold him by the scruff as he carried him against his chest, because he didn't like being carried. Sammy looked terrified.
Not ten minutes later, driving home, we got a call from the vet. I knew immediately. They'd tried to do the xrays and he started foaming from the mouth and died. I still feel awful for not being there. He didn't trust people. I should have been there. They did an autopsy and didn't see anything that really stood out. The vet felt responsible, I think, and spent a lot of extra time on him. She sent off some tissue and fluids and the lab said he had a congenital heart problem.
I'm already wordy tonight and now this... lol... It's kind of theraputic. You'll know. If it comes to that, she will tell you. I will keep you both in my thoughts.