Hi. I have a 4yr old shih tzu. He hasn’t been eating for the past 2-3 days. A little here and there of chicken. About a month ago, he started showing signs of weight loss. He stopped eating and was ‘blah’ every day for a week. We took him to the vet and had blood work, x-ray, and an ultrasound done. All that confirmed an ‘overgrowth’ of bacteria in his small intestines. I am trying to get the paper work with all the work done so I can confirm what was actually done or not(my sis has it). We were giving anti-bacterial meds for the little guy. After a week and a half of the meds, he began showing strength. He was up and moving and even wanted to go for a walk. He even started to eat a mixture of chicken and dog food(a little hard and soft). We gave him food little by little so he can get used to it. About 3-4 days after he showed positive signs, we’re back to square one. Does anyone have any idea what this may be? The vet now says, it ‘might be IBM’. I assuming, she meant IBS (irritable bowel syndrome). And this is her guess and she said she wants us to see an internal specialist.
Vet ruled out EPI , pancreatic

Thanks for all the help :)

You need to find out what is really going on. There is something called IBM.

https://en.wikipedia.org/wiki/Inclusion_body_myositis

Sadly there are no vets on this site, so anything we advise would be a best guess, not a diagnosis.

The link cdad posted is IBM in humans. I couldn't find anything about IBM in dogs. I wold ask your vet for information about her diagnosis, what it means, what the prognosis is, what you can do about it, what tests need to be done to confirm it. Etc. Don't be afraid to ask questions, even if you think they're silly. You're not a vet, so asking questions is normal so you can understand what's going on.

When is your dog going to the recommended specialist?