Diet was the last thing that got TP's kidneys unless it was super high sodium. By his own admission he was on tons of ibuprofen (8-10 tabs 3-4 times a day) for joint pain (search on **broken link removed** ) for kidney damage and ibuprofen.
But... the same things that kill a kidney in an aging person do in a bb'er, high BP, dehydration, thickened blood from androgen use, he was known as a big user of ECA, and clen also (people say)-nubaine, and high doses of AAS and he did use GH.
Plus as mentioned by AWN2004 above the extreme dehydration and water restrictions from contest prep and diuretics murders the kidneys.
But HIGH PROTEIN diets in themselves don't damage kidneys.
Add all that stuff up and you get kidney failure by the age of 35.
While I don't feel TP was "ALL DRUGS" they did play a part in his physique he never really discussed doses but did mention he gradually went higher and higher as he progessed in his career. He did mention he was on 600 mg Deca and 400 mg Test for the Ironman after his kidneys went down and he had to stop. And that he took GH but it was well after he won his pro card.
As far as TP's condition today he's on 100 grams of protein and dialysis and in kideny failure and not training.
People with no kidneys are very sick and in constant catabolism with mineral and water balances coupled with high levels of creatine and other waste products it's no wonder he is very very small.