I have a friend (she actually has two of my puppies) anyway, she has a friend who has a very small yorkie. It was about 6 or 7 months old. All of a sudden it got sick throwing up and then diareah. They rushed to the vet, had her on iv fluids, and once diagnosed were in route to UC Davis for treatment. The puppy died on the way. Here is a link for what it was diagnosed with. Wow, so scary.
Hemorrhagic gastroenteritis - Wikipedia, the free encyclopedia