Diarrhea

Question
My golden started getting diarrhea bouts about 5 months ago.  He turned 2 nov 07.  It only last less than a day and it's gone.    But, what is realy weird is it's comes back every 30 days or so.  We have taken him to the vet and they where no help.  They gave us meds for diarrhea and said everything else looks fine (rectal exam). They did give him a rare worm treatment.  But if it was worms why would they both him once a month?  Their is blood buts it red fresh blood like he poping a blood vessel.  That stops real quick (the bleeding).  Is this common in this breed?

Answer
Most Goldens don't have such troubles.  I think you really need to study what is happening just before the episodes.  Could an indigestible be available for foraging on a monthly basis?  Study his environment for anything that changes just before the problems.  Could he be eating sanitary napkins?