A Small Dog Who Has Vomited for a Year and Lost Almost Half His Weight

It's clear you've already been through a great deal to find answers for him. Going from 16 to 9 pounds is a loss of more than 40% of his body weight, so this still needs urgent attention, even though he is acting like himself. If he isn't already under the care of a veterinary internal medicine specialist, please ask your vet for a referral.

A dog who eats well but can't gain weight may not be digesting or absorbing his food properly. Ask whether he has had these tests: a pancreatic function test (for exocrine pancreatic insufficiency), vitamin B12 and folate levels, a blood test for Addison's disease, and protein levels to check for a protein-losing gut disease. If biopsies were taken during his surgeries, ask what they showed. If not, endoscopic biopsies may help. A strict diet trial with a hydrolyzed or novel-protein prescription diet is often part of the plan.

It also helps to tell your vet exactly how the food comes up. Vomiting involves heaving. Regurgitation comes up effortlessly, often soon after eating, and points to an esophagus problem instead. A short video can be very useful. Small, frequent meals of a calorie-dense food your vet recommends may help him hold weight while the cause is found. Weigh him weekly and keep a log of episodes.

See why dogs throw up and upset stomach in dogs.

This is general information, not a diagnosis. Please follow your own vet's advice.