Kidney stones are small pieces of stone that form in the kidneys. They may be painful or not. Kidney stones are tiny crystals that form in the kidneys and pass out through urine. They are hard lumps that develop inside the kidney. A kidney stone is a solid item that is created from urine-based compounds. Kidney stones can be made of calcium oxalate, uric acid, struvite, or cystine. A kidney stone may be treated with shockwave lithotripsy, ureteroscopy, percutaneous nephrolithotomy or nephrolithotripsy. Common symptoms include severe lower back pain, blood in the urine, nausea, vomiting, a fever, chills, and bad-smelling or cloudy-looking urine.