Dr. Norsworthy's theory is that the presence of vomiting alone or vomiting with weight loss indicates that small bowel thickening
causes hypomotility, which is deficient motility or movement of all or part of the GI tract.
If your veterinarian does not hear anything then the dog vomiting and diarrhea could be
caused by fluids in the digestive system passing quickly through the body (called
hypomotility), blockage of the small or large intestine (ileus), fluid that accumulates or inflammation of the tissue that lines the abdomen (diffuse peritonitis).