It has been my experience that Sugarcatmom (and Growler) has more knowledge about cat nutrition than any vet I have had over the years. Any vet that recommends a dry food for a constipated cat, or one in kidney failure does not know a whole heck of a lot about cats
. Cats get their food from moisture (as all animals actually). They don't have the luxury of cups. I just don't understand why vets don't get that
Think about yourself eating crackers all day, then licking up water for your moisture, not hard to believe that you won't be very hydrated
.
It is a fact that vets don't get a whole lot of training on nutrition and what they do get is from cat food manufacturers.
Your cat's issue could actually be with the nervous system which is not moving the bowels properly, if that's the case, then a low residue food is would be the best diet and that would be a raw diet with minimal bone in it. I find with my cats, even a quality canned doesn't produce as small poops as raw does.