I'm sorry you didn't get an answer before.
My own dog (who passed away in 2012) was diagnosed with 'early-stage' kidney failure in late summer 2011. Her only symptoms were drinking more than usual, and wetting the bed! This came on suddenly.
Her BUN and creatinine were elevated but not phosphorus. All her other blood values read 'normal.
Her energy, love of life, and general condition were excellent.
The vet immediately put her on ACE inhibitors (to increase renal blood flow) and a renal diet. The diet was quite strict but as weeks went by and her elevated values dropped somewhat, she was allowed treats like scrambled eggs, chicken breast, white fish, as well as the prescription diet. And she was always allowed vegetables.
This had results within weeks. Within days she stopped wetting the bed (I used doggy-diapers for those few days, and prior to her treatment, which was not a long time of her wearing diapers but they helped a lot. I also bought incontinence sheets for the bed. They were very useful. All I had to do was take off the top sheet in the morning and wash it, and wipe down the plastic incontinence sheet, before putting a fresh sheet on top.)
Okay, within days the treatment was starting to have some effects and she stopped wetting the bed. I measured her water intake every day, and that started to drop too.
On her first month check, the BUN and creatinine values had come down.
On her 2-monthly check they had come down again. By early Spring 2012 they had come right down to mid-normal. The vet said he would never have known she'd ever had kidney problems. She was happy, healthy and well.
Unfortunately (and no-one saw this coming) she passed from Hemangiosarcoma that June, aged one month short of 15.