A new type of artificial urinary calculi: in vitro study by spiral CT.

RATIONALE AND OBJECTIVES: Artificial urinary calculi similar to natural stones have long been sought in urologic research. In an experimental study, the authors assessed the CT characteristics of a new type of artificially produced urinary calculus [BON(N)-STONE]. METHODS: Six different types of urinary calculi (uric acid, struvite, cystine, calcium oxalate, brushite, and apatite) were produced by a coating technique in which several layers of a suspension of pure substance were applied around a core and dried. A total of 60 stones (10 per group) were studied by spiral CT at two energy levels (100 and 120 kV, 250 mA) with 1-mm slice thickness. RESULTS: All calculi showed a small hyperdense core surrounded by a homogeneous matrix and a slightly hyperdense outer rim. From the least to the most dense, the stone types were uric acid, struvite, cystine, calcium oxalate, brushite, and apatite. Absolute CT values at 100 and 120 kV could differentiate between all groups of stones at a significance level of P < 0.001 or better. Attenuation values were in a comparable range to reported values for natural stones, with the exception of uric acid and struvite, which were notably lower. CONCLUSION: These artificially produced urinary calculi showed properties similar to those of natural stones. Thus, this seems to be a promising stone model for further investigations.