personally myself I would make sure the vet has tried every other possibility & also try different diets. And I would also get a second opinion as well.

Talk it over w/ your vet to see what other diets or additives can be given to help your dog w/ the anal gland problem but will have the less chance of upsetting his sensative stomach.

My rott had the same problem for the first 3.5 years i had her she was in every 2-3 weeks she was reccomended to have the surgery so we went off to be seen by 5 other different vets & each suggested the same because we have already tried everything & anything. I decided to wait it out a little longer as i did not want to take the chance of her loosing control of her bowel movements a few weeks later I switched her food to nutro natural choice for large breeds and the problem dissapeared (along with many other problems). Even a simple diet with no addatives/supplements may help.