
Thanks for the reply :)
I've joined a Megaesophagus group, and it seems that a fair few cases occur in adult dogs - 25% of those cases are caused by Myasthenia Gravis, which was one of the conditions my Dobe was tested for.
Fingers (and paws!) crossed for my boy, although it seems that if a pup is born with MegaE then prognosis is often better than if it occurs in an adult dog with an untreatable cause, as esophagal function can improve as they mature.
The link between general anaesthetics and megaesophagus is in esophagitis (which can cause muscular weakness) caused by gastric acid refluxing into the esophagus.
A little while after the regurgitation started it was actually treated with medication as a case of esophagitis. If an endoscopy had been done early on before medication and time had passed (which wouldn't have happened as it makes sense to try to treat it before resorting to another GA!) there may have been obvious signs of esophagitis still remaining from the surgery. We'll never know, and what's happened has happened - it's just frustrating to not know why! Our vets have been really good, and were even open to talking about the surgery link which I was pleasantly suprised about!
Some good general links I found anyway, just incase anyone is interested or is searching the board in the future :)
http://www.michvet.com/library/medicine_megaesophagus.asphttp://www.gcvs.com/internists/megaesophagus.htmhttp://www.caninemegaesophagus.org/What_is_MegaEsophagus.htmlhttp://www.lowchensaustralia.com/health/megaoesophagus.htmhttp://www.vetsoftware.com/acvc2002-willard5.htm