It's liver toxic, just as much as any 17alkylated oral, but I haven't heard of it being hard on the kidneys (unless it raises your blood pressure, then it would be).
Lots of people will probably jump in here and say, anavar isn't as liver toxic as <x-oral> however I don't believe that to be the case if you are comparing it to other 17alkylated orals that don't have liver toxic metabolites, mg for mg, 17alkylated is 17alkylated.