#AUA14 - Correlation between CT density, biochemical structure and microcomposition of urinary stones - Session Highlights

ORLANDO, FL USA (UroToday.com) - CT plays a significant part in determining the biochemical composition of urinary stones. Heavy metals and trace elements are involved in stone microcomposition. This study was carried out to evaluate the relationship between CT density and both biochemical structure and microelemental composition of urinary stones.

auaAfter preoperative CT evaluation for mean density, 125 renal stones were retrieved after endoscopic and open procedures. These stones were pulverized and divided into 2 equal parts for completion of 2 modes of analyses. The first half was analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES) to determine microelemental composition (22 elements/stone). The second half was submitted to Fourier transform infrared spectroscopy (FT-IR) in order to determine the biochemical structure.

The study enrolled 69 males and 56 females ranging in age between 8 to 83 years. Stone size ranged from 12 to 60 mms, while CT scan density ranged from 230 to 1744 HU. With ICP-OES analysis, stones with high CT density (e.g., calcium (Ca) oxalate monohydrate) showed significantly high concentration of: B, Ca and Pb (P 0.001, 0.001, 0.016 respectively)—while stones with low CT density (Ca oxalate dihydrate, urate and Ca phosphate) had higher concentration of: Ba, Cu, and S (P 0.048, 0.025, 0.048 respectively). With FT-IR analysis, the biochiemical structure revealed 22 mixed stones, 32 uric acid, 46 oxalate, 19 phosphate, 3 struvite and 3 cystine stones. All stone types had significantly different concentration of the following heavy metals (13 elements); B, Ba, Ca, Cu, K, Mg, Na, P, Pb, S, Se, Sr, and Zn (P value < 0.001, < 0.001, < 0.001, < 0.001, 0.033, < 0.001, < 0.001, < 0.001, < 0.001, 0.016, < 0.001, 0.022, < 0.001, < 0.001 respectively).

CT scan density was dependent on biochemical and elemental stone composition. In particular, the authors found that density was especially affected by the concentration of Ca, Ba, B, Mg, P, and S. This analysis was likely made possible with recent improvements in the power of imaging technology. The significance of these trace elements in the pathophysiology of stone disease is unclear. Further, the clinical application of ICP-OES for stone microanalysis may deserve further study.

Presented by Mahmoud El-Naggar at the American Urological Association (AUA) Annual Meeting - May 16 - 21, 2014 - Orlando, Florida USA

United Arab Emirates

Written by Eric Ballon-Landa, BA, University of California (Irvine), and medical writer for UroToday.com