If you are seeing these signs, contact your veterinarian — they can determine whether it's gastroenteritis and how to treat it. Signs of gastroenteritis in dogs may include:
Vomiting
Decreased appetite or disinterest in food
Abdominal discomfort (hunched posture, whining, restlessness)
Decreased drinking or excessive panting (signs of dehydration)
Lethargy (decreased energy)
Bloody stool or persistent vomiting can be a medical emergency — contact your veterinarian immediately.