Stones are not so good for kidney stones… Cornstarch was, for me. Immerse cornstarch in just enough water that it holds its shape. Then, immerse your hand holding the cornstarch stone in running water, and dissolve the “stone” in your hand, while reciting appropriate texts or words for the release or anger and hurt and pain, and for the appearance of healing. Continue whatever treatments are prescribed by your doctor, but perform the cornstarch dissolution daily until you pass the stone.
Clear quartz (cleansing) and hematite (grounding) would be good. Some basic searches on Google brought up garnet, carnelian, bloodstone, and flourite as appropriate for kidney ailments. YMMV of course since crystal and gem associations may not always fall in line with books or website recommendations.