I do not know anything about kidney issues but figure out if you have changed any product you use within a week or so of the beginning of the itching. It easily could be a fragrance or chemical within the product.
It could also be severely dry skin. For the dry skin.....try coconut oil. It is pure and contains no additives. You could also exfoliate the skin by rubbing the skin using sea salt (fine grade), olive oil, and corn meal mixed together in equal portions. If you do this in a shower or bathtub make sure you stand on a rubber mat to prevent slipping and clean the oil out of the tub right after doing this. This removes dead skin cells and leaves the skin really soft. Do not wipe off all the oil when drying just pat the water off. This works really well.
Get checked for kidney function - unusual/unstable blood chemistry can have this effect, also the type of soap you use to bath with, type of laundry detergent, all sorts of things can cause itchiness