Well after losing Ruby to renal failure last week. Initially thought to be caused by a very low grade infection my vet is now leaning towards poisoning because the onset was so quick and severe.
I took my boy in for a routine blood test just to ease my mind as he is the fittest, healthiest, most playful dog you could ever meet....and the results are back.
Very mild kidney problem. It is looking more and more like poisoning as my boy had bloods done 6 mths ago and he was fine.

Creatinine - 127
Phosphorous - 1.2
BUN - 17.7

My vet is putting him on Royal Canin and Ipakitine.

Is there anyone else on here with a dog with renal failure/kidney problems and what make of food do you use.

Ive been doing some serious research for the past hour or so and Ive come across many articles that say that dogs that are fed a mainly raw diet naturally show elevated signs of BUN even though they are perfectly healthy and on reurning to a dry kibble diet the BUN levels return to within normal range. Does anyone have any knowledge/experience of this as My boy has been on 3/4 raw and 1/4 kibble for months.

Raw will contain high levels of phosphorus which may affect the blood results.  It's unwise to feed bones to dogs with kidney problems - the best is low phosphorus, higher fat with good quality protein.  There have been other threads on this so worth checking out.  If you're feeding your own diet - rice, breast of lamb and chicken legs, cooked and fed with skin are good foods.  Feed with calcium (ground eggshells or tums indigestion tablets NOT calcium tablets as they have vit d in which combats the reason you give calcium which is to prevent absorption of phosphorus).  Also feed vit B, C and whole fish oil separately to the calcium as the dogs need vitamins.  Don't feed fish liver oil.  Careful of not feeding enough protein as this is as bad as too much phosphorus.