This has been addressed in these threads on the research forum:

http://forum.lowcarber.org/showthre...&threadid=52311

http://www.benbest.com/health/kidney.html

This study shows that raising dietary protein in a healthy person raises risk of dying from kidney disease less than 1%.

http://www.ncbi.nlm.nih.gov/entrez/...9&dopt=Abstract

On the other hand, kidney stones (which are not life-threatening) are a possibility on a long-term ketogenic diet as evidenced in epileptic children who must use the ketogenic diet to control seizures. The risk is greater when a person doesn't drink enough water or eat enough green vegetables.