Sometime between age 10 and 11 our Yorkie started having bouts of pancreatitis. Then, he started having bowel issues.
The vet had us do one thing, then another. No one ever suggested, much less checked for, cancer. STUPID VET! and STUPID me! The last straw was when blood vessels exploded in one of his eyes and the vet said he had an eye infection. Gave us antibiotic cream.
Scruffy got worse on a weekend and we rushed him to the emergency vet.
They stabilized him and the next day broke the news to us that he had hemangiosarcoma. (cancer of the blood cells)
It had progressed so far that he could no longer breathe without oxygen. They said they could try to treat him, but it would have only given him another month or two, tops, and that, he would spend miserable and trying to recover from the treatment.
We put him down that afternoon.
While this cancer is virtually impossible to survive, if you catch it soon enough, chemo does work. I wish we'd had the chance to try.
Whenever your dog has a series of issues, of any kind -- even if they don't seem like they could be related -- ask for blood work and ask specifically about the "c" word.