A small, hard deposit that forms in the kidneys and is often painful when passed. Kidney stones are hard deposits of minerals and acid salts that stick together in concentrated urine. They can be painful when passing through the urinary tract, but usually don’t cause permanent damage. The most common symptom is severe pain, usually in the side of the abdomen, that’s often associated with nausea. Treatment includes pain relievers and drinking lots of water to help pass the stone. Medical procedures may be required to remove or break up larger stones.