Kidney stones, also known as renal calculi, are hard mineral deposits that form in the kidneys and can cause significant pain and other symptoms when they pass through the urinary tract. These stones can vary in size and composition, but most are made up of calcium oxalate or other substances like uric acid. Kidney stones can form when there is an excess of certain minerals and salts in the urine. Common causes include dehydration, a diet high in certain foods (such as oxalate-rich foods like spinach and beets), and certain medical conditions. Kidney stones may not cause any symptoms until they move within the kidney or enter the ureter, the tube connecting the kidney to the bladder. When this happens, symptoms can include severe pain in the side or back, lower abdomen, or groin, pain during urination, blood in the urine, and frequent urination.