A few things come to mind as we have dealt with this in the past with our dogs. Has your dog been treated for whipworms? Sometimes a fecal test won’t show positive for whipworms as they go on a cycle, but the dog may still have them, and throwing up is one of the main symptoms. A dog may also have a rough coat, blood in the stool, etc., but not always.
Did they do an ultrasound and bloodwork to rule out a blockage or cancer?
How is the vomiting being managed? There is a drug, cerenia, which is a dog motion sickness drug that is often prescribed for vomiting. It really helped one of our dogs. She was miserable with vomiting, and this drug controlled it when nothing else worked. I don’t know how long a dog can take this drug, but the vet should know. A couple of other things that helped were Perfect Form, a supplement made by The Honest Kitchen as well as the Honest Kitchen dog food. You might also talk to a holistic vet.
If all the above issues have been addressed, I would ask the vet about IBD. One nutritionist develops homemade diets for dogs that end up with this diagnosis, as well as other things. Her name is Monica Segal, and she has a blog as well as a yahoo group.
Hope this helps.
