My dog vomited a lot of yellow watery fluid without warning after eating sausage at noon — what’s wrong?

Vomiting yellow fluid can have many causes, such as gastroenteritis, parasites, poisoning, or viral disease. Given the dog’s preexisting poor appetite, an underlying gut problem is likely, so take it to a vet for fecal, abdominal ultrasound, and virus screening.

If a visit is inconvenient, withhold food, and after vomiting eases give pet anti-emetic and anti-inflammatory medication; if no further vomiting, feed small frequent portions of mild foods like millet or minced-meat congee, and consult a vet if vomiting continues.