I am so sorry to hear about your min pin. I hope you can find comfort in knowing you did everything you could..........sara
First of all I am sorry your dog died, poor little thing. And obviously you did your very best to help him. It is very sad, and I know how you must be feeling.
Maybe there were two things going on. Two completely separate problems. To be passing dark urine like that, he must have been excreting blood cells in his urine. This could possibly have been Haemolytic Anaemia. This can be inherited.
But the vet seemed to be focussed mainly on the bacterial infection.....It does baffle me a bit. Antibiotics are not going to cure Haemolytic Anaemia, if it was that!
You did your best, I am so sorry things turned out like they did.