I have a friend who had a dog with pancreatitis. She was neither old nor overweight when she got it, and she hadn't gotten into anything that would normally cause an acute attack. The immediate regurgitation would have me worried. Either his esophagus is so raw that anything he swallows causes immediate vomiting, or something (perhaps one of the lymph nodes) is blocking his esophagus. Did they look at the esophagus itself, or just the stomach? A tumor won't show up on an x-ray. I'm keeping my fingers crossed that Harvey's system has just gone temporarily haywire...