there are no kidney issues with tren. its a myth. the tren HEX ester allegedly bears some kidney toxic properties, but since nobody gets real tren hex anyway that doesnt matter
obviously tren has some water shedding qualities so make sure to drink alot to avoid dehydration on it, dehydration causes kidney issues.
I read that kidney issues was with people converting finaplex pelets with bathtub chemistry methods. The impurities would stress the users kidneys.
Also tren is known for discoloring the urine but this is supposedly harmless, kind off like taking a mutli makes your pee green.
Btw out of the two i think most people would tolerate tren much better. anadrol is usually run for 4-6 weeks max and still a lot of people report discomfort, loss of appetite etc.. Basicly feeling toxic.
On the other hand tons of people have run tren for months without serious issues.
Im aware of studies showing people taking high dosage of anadrol for months and be fine, but very very few people have been able to do that when it comes to using anadrol for a bodybuilding purpose.