Holistic kidney advice needed

Hello.
I don't know if you can help. I just need some advice. I have about four years back issues of Dogs today magazines and I'm sure you have covered this before, so if you could point me at the right issue that would be good. If not I will go through them all! It won't be a hardship!
My beautiful boy Bosley dog has had a problem with incontinence that has got worse lately. For a while he has been treated with propanol syrup which worked at first.
He became that way when he was 14 and had to have an MRI scan.
We think they may have pumped too much fluid through him while he was under and it broke him a little bit (The vet sort of confirmed this).
For the last few months he's got worse. It's like a leaking tap and happens when he is asleep mostly. He sleeps a lot these days as he is nearly 16.
He has been in the vets today for an ultrasound and more blood tests.
The blood tests have shown up possible kidney disease but not definite as the results were not strong enough as it is not advanced enough.
But all the symptoms now point to that too.
Urine samples show it's very diluted indicating that the kidneys are not doing their job.
The ultrasound showed that his kidneys were shrinking too.
His back legs have started dragging a bit and we think it is connected.
He is also very stiff and his front legs give him trouble sometimes.
He has been on loxicom for that but after today the vet says that he can't have that as it's not good for kidney problems. He now has 2 tramadol to take a day (I will be googling those tomorrow).
So basically what I am asking is if anyone knows of any holistic remedies that we can give him to help his kidneys?
Our vet has put him on another Hills prescription food, and while I do trust our vets I would like to know if there is anything else I could do to help him.
He's so happy most of the time, still has lots of puppy moments and our life revolves around him.
I know he's old and I have to face the inevitable but we just want to help him as much as we can.

Thanks.
Sue Bridle
Further to this, have you heard of a product called Tripsy that is available in the US? It is herbal and it treats kidney failure. I just wondered if you knew anyone who has had experience of it? There are lots of good reviews but you never know if to trust them!