Prediction of calcium level in melamine-related urinary calculi with helical CT: diagnostic performance evaluation and clinical significance

• Published in: Urolithiasis 2012-06, Vol.40 (3), p.231-235
• Main Authors: Yuan, Li, XiaoRui, Ru, Gang, Huang, XinSheng, Xi, XiaoGang, Huang, Li, Dong, YiRong, Chen
• Format: Article
• Language: English
• Subjects: Calcium - analysis; Humans; Medical Biochemistry; Medicine; Medicine & Public Health; Nephrology; Original Paper; Performance evaluation; Retrospective Studies; Tomography, Spiral Computed - methods; Triazines - toxicity; Urinary Calculi - chemistry; Urinary Calculi - diagnostic imaging; Urinary Calculi - therapy; Urology
• ISSN: 0300-5623; 2194-7228; 1434-0879; 2194-7236
• DOI: 10.1007/s00240-011-0413-7

The aim of the study was to investigate the relationship between CT-attenuation and stone calcium level in melamine-related urinary calculi (MRUC). A total of 25 MRUC with known composition and calcium level were included (11 uric acid stones, 2 calcium oxalate stones and 12 mixture stones of uric acid and calcium oxalate). Of all, 18 renal stones accepted alkalization therapy except for 5 lower urinary tract stones and 2 stones of unknown position. With well-matched composition, 61 adult urinary stones were included as controls. Every stone was scanned by helical CT (80 kV/120 kV, 300 mA, pitch 0.625 mm) and the highest CT-attenuation value measured. CT-attenuation values of MRUC increased gradually from uric acid stones, mixture stones to calcium oxalate stones, but were always lower than the values of controls. Furthermore, a strong positive correlation was found between stone CT-attenuation value and stone calcium level ( n  = 25, r 80kV  = 0.883, p  = 0.000; r 120kV  = 0.855, p  = 0.000). Compared with alkalization-therapy-alone group, stone CT-attenuation values and stone calcium level in the comprehensive-therapy group were significantly greater (CT 80kV 1,057 ± 639 vs. 172 ± 61 HU, p  = 0.001; CT 120kV 783 ± 476 vs. 162 ± 60 HU, p  = 0.001; Ca 19.83 ± 7.48% vs. 1.30 ± 1.51%, p  = 0.000). Fisher’s exact test suggested that the stones with higher CT-attenuation values tended to resist alkalization when 400 HU served as the cutoff value ( P 80kV  = 0.002, P 120kV  = 0.000). In conclusion, the study was the first to illustrate that the CT-attenuation value could reflect calcium level in MRUC and found that stones with higher CT-attenuation value were not amenable to alkalization because they probably contained greater calcium. For those patients, we believe that comprehensive therapy will be the best choice.