From what i understand when i was really trying to learn about tren before starting my cycle, most "gurus" says that if you stay with 6 weeks of tren and a very maximum of 8 weeks (wich is not reccomanded by many) kidney troubles should be little to non excistant.
It was also recommanded that you up your water intake by a gallon while on tren. You can check your status when you p. If its dark brown or even intense light yellow, your drinking too little, up your water inntake until your p is close to clear. The only exception is in the morning, then its quite hard to not have a color on your urin, but the rest of the day, go for the clear look.