I’ve blasted up 800mg tren e week and100mg tren a day at the highest for a few months in the past. I’ve taken tren at varying dosages for lengthy amounts of time and it has never effected my liver or kidneys. It turns your pee brown because of metabolites. I’d worry more about cholesterol with tren than liver or kidneys. B12 can turn your pee Orange but it doesn’t mean it’s bad for your kidneys. I ran tren for over a year straight in the past and it didn’t effect my kidney or liver values.
Actually now that you mention it, when I use to take vitamins, same thing happens, dark yellow pee so maybe that’s not necessarily a negative indicator.