I can tell you from personal experience that homeopathy does work. I was then so fascinated by that I went and studied it for 4 years.
The good thing about it is that it has no side effects, whereas herbs might. Herbs may also interact with anti-rejection medication, whereas homepathy will not. He would probably need to take a liquid remedy once a day to have an effect, as this is both strong and gentle so that it can cut through the durg layers.
I would suggest that he goes to see a classical homeopath. Have a word and see what they can do.
Also, acupuncture can be great and can be used to treat the kidney energy, which in terms of Chinese Medicine, would be greatly depleted in a person with renal failure.
Good luck with what ever you decide.