I just wanted to say how sorry i am for the loss of your fur baby.There could have been an underlying problem like Ginger said.You will be in my prayers.May God Bless You and your family...Chan
I send you my deepest sympathy. It is sad and hard to lose a member of your family, as I'm sure he was. He was a good dog I'm certain, and was well loved.
I agree with your decision not to do a necropsy. I don't think I would want that done either, under the circumstances. Of course, without one, you would never know as an absolute fact, what he died of. He didn't suffer very long at the end, and that is a blessing I suppose.
I wonder if it was an abdominal aneurysm, or some 'ballooning' of the Portal Vein? Things like this can be 'silent killers', in both humans and animals. They often show no real symptoms, can hang in there for ages, but just as easily can suddenly give way.
But of course I can't really know what it was, any more than you can.
Anyway, treasure your memories of him. I am very sorry.