I once had a beagle / dauchsund mix and she died of very similar symptoms. She was in a boat and thrown from one side to the other when it turned unexpectedly at a high rate of speed. She seemed fine at first but little did I know that she actually had internal damage to her kidneys. They started to shutdown and after a week I knew something was wrong. She lasted about 5 days after that with intrevenous fluids and hospital care.

Only your vet can truly say what was wrong and why your pups died. However, if you recall did anything happen to them during their last few weeks or so that could of caused internal damage?

As for getting another dog, my suggestion would be do it, do it, do it. There is a greater joy in loving a pup than worrying what might happen when you have one. I have had several since my episode and would not trade any of them for tons of gold.