A variety of factors can make a person susceptible to stones in the urinary tract. Risk for stones is higher in those with family histories of stones; those who have urinary tract infections, kidney disorders and metabolic disorders such as hyperparathyroidism, cystinuria (too much of an amino acid called cystine) and hyperoxaluria (excess production an oxalate salt); and those with a disease called renal tubular acidosis. Another risk factor is absorptive hypercalciuria, in which the body absorbs too much calcium from food and dumps the excess into the urine. High levels of urinary calcium lead to crystals of calcium oxalate or calcium phosphate, which can grow into painful stones.Various laboratory tests and a family history should allow your health care professional to determine a likely cause. You can then make dietary changes to prevent future stones.