It sounds like the ulcer was at work long before it started bleeding or perforated. People can have ulcers perforate after time as well. Prednisone may not help stomach ulcers, and may worsen them more quickly, but this sounds like it was more advanced to begin with. It was also a very small dose that should not have affected the stomach as severely as higher doses that could have been given. The dark stool means it was ulcerated for at least 12-24 hours already.
Toby may have had something called Cushing's disease, where the body pumps out more steroid hormones than it should. Bacterial infections, just like in people, have also been linked to bleeding stomach ulcers in dogs. Certain cancers can definately ulcerate much faster than a stomach wall that is infected or inflamed. Sometimes, you never know what caused it.
Metronidazole is an antibiotic that's great for intestinal bacteria, as well as reducing GI inflammation.
Once you know you have a bleeding ulcer, it can perforate at any time, or never. There is no predictive value on this.
I am so,so sorry for your loss, and for your rapid loss. You never expect a 9 year old little dog to pass quickly, you think you have years left.
While the above describes potential causes of the ulcer, that can only be elucidated with a full necropsy (autopsy). Ulcers can turn that quickly. It is nothing you did prior to bringing him or by bringing him to that hospital. Please do not blame yourself. It definately sounds like you, and his attending vets, were right on top of his situation, and doing everything possible.
Please let me know if there is anything else I can do. I wish you strength, in this very difficult time.
Dr. Chenoa
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