Commonly called kidney stones, [url=http://www.homeherb.com/moresupplements/s229/urolithasis.htm]Urolithasis[/url] means stones in the urinary tract. These stones occur four times more often in men than women. The pain of having a stone has been compared to that of childbirth. The stones can be made of calcium, uric acid, oxalate, struvite, or cystine. Crystals that form in urine and build up on the inner surfaces of the kidney can form stones in the kidney (nephrolithiasis), the ureter, or the bladder. These stones may contain various combinations of minerals and other chemicals, some of which are derived from a person's diet. Gallstones are produced in the gallbladder and are different from those formed in the urinary tract.Although obstruction of the urinary tract often occurs, it is usually temporary and causes no lasting damage. In some cases, however, particularly if the obstruction progresses silently, infection may occur, which can be serious and which warrants prompt attention