Studies have shown that an amino acid extract of white button mushrooms (agaricus bisporus) called Champex improves kidney and liver function in kidney failure patients. It works in part by removing ammonia from the blood and lowering uric acid levels and improving symptoms of gout. It removes other toxins from the body as well.
http://www.sterlingorganics.com
sells a product called Quantum Kidney Complex which contains
the Champex extract and some other kidney friendly herbs.