Trace elements in urolithiasis

Abstract

Trace elements are essential substances, whose content in the human tissue is less than 50 ppm (50 mg/kg). These elements, such as zinc, copper, nickel, iron, and strontium, are able to form poorly soluble salts with oxalate and phosphate ions. No pure urinary stones consisting of these compounds are known so far. However, the incorporation of zinc phosphate (hopeite) in layers in a struvite stone has been described. Organic stones, such as uric acid, contain only small amounts of trace elements.Compared to calcium oxalates, the concentration of zinc and other trace elements is higher in calcium phosphate stones. Trace elements can contribute to the stabilization of calcium oxalate dihydrate (weddellite), an unstable compound. The disintegrati n of calcium oxalate monohydrate (whewellite) by shock wave lithotripsy (SWL) is supposed to be improved by the incorporation of trace elements. An incorporation of trace element compounds in layers or also the replacement of calcium in the crystal lattice of whewellite can be responsible for this effect. In conclusion, depending on the stone type and according to their occurrence in urine, trace elements are incorporated into a urinary stone and can affect its properties.