My dog keeps regurgitating food!

My dog is a 2.9 year old, neutered male Romanian rescue (image attached for reference). A year ago he began regularly regugitating his food. We have had him on kibble diet which he would bring up each meal, wet diets with the same result. We finally tried him on a raw diet which has appeared to improve his faeces and reduce the frequency of regugitation but not stopped it. We have been to our vet and tried single protein, added fiber, cut his meals from 2 to 4 small meals a day served in a slow feeder and now a kong. We have had faecal samples taken which have ruled out internal parasites. He doesn't have a blockage because he is still passing faeces and is able to eat meals several days. The regurgitation happens at random. I have recorded the diet and times of day it occurs and there is NO pattern. Physically and behaviourally (apart from being a bit nervous) my dog appears healthy, he passed good faeces and only vomits bile when hungry. I am concerned that he is once again losing weight because of this issue. My vet is reluctant to investigate through GA because of my dogs nervous behaviour, he doesn't cope in kennels and she fears that the recovery after investigation may do more harm than good. I am at my wit's end, I just want to know WHY this happens to him. I suspect that it has something to do with his oesophageal sphincter as food is clearly not reaching his stomach properly. Has anyone come across anything like this before?

Hello!  There exists a condition known as a megaoesophagus in which the oesophagus becomes stretched and food pools within it.  This may be one possibility for your dog (check with your vet) and if found, it has numerous causes.  Even so, it can be a difficult condition to live with.  They do make for challenging anaesthetics but if your vet is loathe to investigate further, I wonder whether they could refer you to someone would be happy to anaesthetise and carry out imaging, or perform other tests (eg for conditions that cause a weakness of smooth muscle in the oesophagus wall) if necessary.

Thank you for the reply Liz, we have ruled out megaoesophagus as that was my first thought too. I guess I will have to go for a referral.