Anal sac problems are not uncommon and their filling can cause the dog to bite at his tail region, scoot his butt acros the floor, refuse to poop, etc. Anal sac problems can be very painful if the sacs do not or cannot drain normally. There can be many reasons why the sacs are not draining and please, rule out the medical first before you go to the dietary. You do not want to worson a medical because you wanted to go the cheaper way out first (this is a geneal "you" not a direct "you" no do not be angered by my use of "you.") First, the ducts draining the sacs may be too small or even close off. The vet needs to check these. I had a dog that developed duct issues and the vet has to periodically go in and open them for me. In severe cases, the sacs may require surgical removeal. Second, infection, growths, etc and being overweight can increase anal sac issues. Rule these out as well. Third, some breeds seem to have a greater predisposition to anal sac issues. Now if the issues are something that you can for now manage, ask the vet to teach you how to safely express the glands. Not hard to learn but should always be taught first by a medical professional and not a groomer. If the sacs do not release with gentle pressure and end up being forced, there can be complications. Dietary – if there are no medical reasons found, then the cause may be dietary. Stools that are too small or soft may not properly help the glands express. Alway, feed a high quality diet – more digestible and less garbage. If the stool are very small and the dog not naturally expressing the glands, increase the fiber the dog is getting. A bit of wheat germ (if the dog does not have wheat allergies), some pumpkin, squash or other veggies may help. But again, do not do diet until all medical have been ruled out. And keep a closer watch on the dog for developing issues. The reason the glands are not draining naturally could change over time. In severe cases, removal of the glands may be the only option.