My 16 year old son presented with a kidney stone in his left kidney, then a week and a half later, one in his right kidney, markedly worse pain the second time, and with vomiting. Not able to catch the stone either time, but he's been referred to a nephrologist that we'll be seeing soon. He's somewhat underweight and doesn't fit any of the usual risk factors. Lab work ordered by primary doc came back with trace amounts of blood in urine still, and 24 hour urine collection shows normal lab values, save for cystine, which we haven't gotten back yet. Family history on my dad's side of stones. E.R doc for the second stone said he was making the nephrology referral because due to my son's age and stones in both kidneys so closely timed, he suspected cystine stones. If all other lab values have come back normal but we don't yet know his cystine levels, does that pretty much point to cystine stones?