Gastritis is fairly common in dogs, particularly in longstanding small breeds, like miniature poodles, Lhasa Apsos, and Shih Tzus. It can still occur in larger breeds, however. Because gastritis is sometimes a symptom of a more serious condition, seeking a vet is a good idea to ensure that the source of the problem is identified and resolved.Gastritis is the technical term for an upset stomach. This can look like intermittent vomiting, stomach pains, or irregular eating habits. Gastritis occurs when the inner lining of your pet's stomach is irritated, either by chemicals, medication, allergens, infections, or other foreign bodies. Auto-immune diseases (where the body's own immune system is fighting itself) can also cause gastritis.