The mechanism of formation of renal stone crystals

Abstract

Typical renal stone minerals such as the calcium phosphates and oxalate hydrates may nucleate, grow, or dissolve in the fluctuating concentration conditions of the urinary tract. A study has been made of the rates of formation of these minerals under conditions in which the concentrations of ionic species were maintained constant by the potentiometrically controlled addition of lattice ions. The kinetic studies were made under conditions of low supersaturation similar to those in vivo and, in the case of calcium phosphates, at least three solid phases have been shown to participate in the overall reaction depending upon factors such as pH, nature and concentration of supporting medium, supersaturation, ionic strength, temperature, and the presence of inhibitors of crystallisation. For the calcium oxalates, the mineralisation process may involve the initial precipitation of less stable hydrates before conversion to the most stable whewellite. Urinary stone inhibitors may have a considerable influence in stabilising thermodynamically less stable hydrates.