My dog had similar issues; I did the de-worming, tried several different kinds of dry and wet food, vet ran test and tests and tests and said he was fine every time, etc. I switched him to raw/B.A.R.F. and have had no problems since. It's been wonderful. May or may not be the solution for Bruno, but it's worth a look in the B.A.R.F. forum in here. Good luck!
Ralphie - GSD, rescue, Gotcha Day 2/10/13
Nightshade - born 6/3/2003 - Domestic medium hair/Maine Coon mix (feline)
James - Domestic short hair (feline), rescue, Gotcha Day 6/23/11