Hi!
This is my first post here!
This happened to my little Morkie Ava just yesterday. She had soft stool in the morning, wasn't interested in eating and drank a lot. Throught the day, it got worse, and she also started shivering. I called the vet right away, and got her in within the hour.
The vet said that there was no specific reason (she was acting completely normal, playful and loving). She gave her some special gastrointestinal food, and sent us on our way. In the middle of the night, I noticed that there began to be blood and mucus in her soft stool. I called the vet in the morning, and she said that it sounds as if it's Colitis, but since she is too small for the meds (3lbs), gave her some fiber food to move the infection through.
She's still having the issue, but have only fed her once with the fiber food a few hrs ago. If it's not better in a few days, we are to go back to the vet.
This is my first pet, and she's only 3.5 months, so it was a very scary experience!