CT, US and MRI of Xanthine Urinary Stones: An In-Vitro Analysis
Abstract Background: Xanthine urinary stones are a rare entity that may occur in patients with Lesch-Nyhan Syndrome receiving allopurinol. There is little literature describing imaging characteristics of these stones, and the most appropriate approach to imaging these stones is therefore unclear. We performed an in-vitro analysis of xanthine stones using computed tomography (CT) at different energy levels, ultrasound (US), and magnetic resonance imaging (MRI). Methods: Five pure xanthine stones from a boy with Lesch-Nyhan were imaged. CT of the stones was performed at 80kVp, 100kVp, 120kVp and 140kVp and CT numbers of the stones were recorded in Hounsfield units (HU). US of the stones was performed and echogenicity, acoustic shadowing and twinkle artifact were assessed. MRI of the stones was performed and included T2-weighted, ultrashort echo-time (UTE)-weighted and T2/T1-weighted 3D bFFE sequences and signal was assessed.Results: On CT, xanthine stones were radiodense and the average attenuation coefficient did not differ with varying kVp, measuring 331.0+/-51.7HU at 80kVp, 321.4+/-63.4HU at 100kVp, 329.7+/-54.2HU at 120kVp and 328.4+/-61.1HU at 140kVp. On US, xanthine stones where echogenic with acoustic shadowing and twinkle artifact. On MRI, stones lacked signal on all tested sequences.Conclusion: Xanthine stones demonstrate imaging characteristics typical of most urinary stones: dense on CT, echogenic on US, and lack signal on MRI. Therefore, the approach to imaging xanthine urinary stones should identical to the approach with other urinary stones.