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Monday, December 3, 2007

Composition and Clinically Determined Hardness of Urinary Tract Stones

UroToday.com - Modern removal of stones depends on disintegration, either with extracorporeal shock waves or with techniques requiring direct contact with the stones. The ease, by means of which fragmentation is achieved, in any of those situations, is determined by the hardness of the stone. Different kinds of crystalline material found in stones have specific properties in this regard and accordingly the relative resistance to disintegrating forces varies with the mixture of salts in the stone. The treatment efforts necessary for a particular stone to a large extent can be assumed to depend on its hardness and volume.

In the era of evidence based medicine and for interpretation of therapeutic procedures, it is important to account for numerous variables that are of importance for the treatment outcome. When different methods of stone removal are compared, it is desirable to include a factor that reflects the average hardness of the stones in the comparison. This is apparently also of great importance when results between different countries are evaluated because stone composition in the treated populations may differ significantly.

A factor that describes the expected hardness of the stone thus is suggested to be a tool for a more appropriate comparison of different treatment strategies. Although the literature contains several reports on hardness of various stone salts, none have covered all common crystal types. This approach requires a qualitative analysis of the stone components, but such a step also is of importance for the complete adequate care of the stone-forming patient. The hardness indices have been obtained from observations with an electohydraulic shock wave lithotripter, but it is not the specific results with that form of treatment that are of interest. The recordings are assumed to roughly reflect the resistance of stones containing defined fractions of various crystalline components.

Written by Hans-Goran Tiselius M.D., Ph.D - Professor of urology - Department of Urology - Karolinska University Hospital and Karolinska Institutet - Stockholm, Sweden, as part of Beyond the Abstract on UroToday.com.

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