Yes, once you're off, kidneys levels should go back to normal. but the older you are the bigger the stress on kidneys ,and like you say, everything Bodybuilding related take a hit on kidneys , add creatine to the equation and you might irreversible damage.
WoooSHHHHHHHHHHHHH VINTAGE
my last blood work was solid (kidney items)
#s ------------------------------------------healthy range
Glucose, Serum 83 --------------------- - 65-99 mg/dL
BUN 17------------------- ------------------6-20 mg/dL
Creatinine, Serum 1.17 --------------------0.76-1.27 mg/dL 01
BUN/Creatinine Ratio 15-------------------- 9-20
super curious to get it again in about a month
make sure you fast 24 hours not, just 12 hours. fast 24 hours at least before bloods and stop training for 3 days prior too