Kidney stones are made of salts and minerals in the urine that stick together to form small "pebbles." They are usually painless while they remain in the kidney. But they can cause severe pain when small pieces leave the kidney and travel through the narrow tubes (ureters) to the bladder.

Symptoms of a kidney stone include severe pain in the flank, which is felt just below the rib cage and above the waist, usually on only one side of the back. The pain may spread to the lower abdomen, groin, and genital area. Other symptoms include blood in the urine (hematuria), painful or frequent urination (dysuria), and nausea and vomiting.