Xanthine and 2,8-dihydroxyadenine kidney stones
These rare stone are almost always diagnoses by stone analysis. Because they are radiolucent (not visiable on plain X-Ray) they are frequently mistaken for the more common radiolucent stone -uric acid. Greater than 8.6 mg/24 hr urinary exceretion of xanthine is abnormal. 2,8-dihydroxyadenine is diagnosed by it presents in the urine and confirmed by a reduced level of adenine phosphoribosyltransferase in the red blood cell.