Yes, but not the main cause, which is prob a diuretic or another toxic oral
The main kidney killer is high blood pressure. Not steroids directly, as in toxic to the kidneys (indirectly they increase BP). The doc probably was referring to the BP increasing aspects of stimulants and he wouldn't necessarily be wrong. But he doesn't know what the cause for "weak kidneys" is for sure, unless he takes the dudes BP before and after a PWO.
hippplito, you can't "clean out" kidneys, you can get the risk factors under control though, as in lowering BP etc. If the kidneys are damaged already they don't really recover.