Enlargement of calcium oxalate stones to clinically significant size in an in‐vitro stone generator

Abstract

Objective To develop and validate an in vitro method suitable for the quantitative investigation of the growth of calcium oxalate stones through to a clinically significant size. Materials and methods Small fragments of calcium oxalate calculi were suspended in a mixed suspension/ mixed product removal crystalliser supplied with artificial urine supersaturated with calcium oxalate. The fragments were weighed at regular intervals until they reached ª 500 mg. The results were plotted as weight against time and fitted to equations corresponding to constant increase in diameter, surface area-controlled and constant-deposition growth patterns. The choice of the most appropriate model was based on the squared regression coefficient ( r 2 ).Results Eight fragments (2-6 mm in diameter) were grown to ª 10 mm in diameter over periods from 137 to 369 h. Seven of the growth curves were best-fitted ( r 2 ≥ 0.988) by the equation w = kt (3/2) + c , where w is the weight, k is a growth constant, t is the time and c is a constant approximating to the initial weight. This corresponds to a surface area-dependent mechanism. Conclusions The growth of these small fragments to a clinically significant size accelerated throughout the experimental period in a way which was consistent with a surface area-dependent mechanism. We have developed a resilient model suitable for studying the kinetics of calcium oxalate stone growth in vitro .

Citrate inhibits growth of residual fragments in an in vitro model of calcium oxalate renal stones

“…Our model of stone growth, while not itself immune from all criticism, is very different from all that has gone before. It is based on a recognized principle, mixed suspension mixed product removal [11], is statistically powerful and robust [13] and addresses some of the deficiencies of other in vitro studies [12].…”

“…The system was based on the stone generator recently described by Ananth et al [12]. Further refinement and expansion of the technique as a "stone farm" allows 12 stones to be grown simultaneously making controlled studies feasible.…”

“…To date there has been no direct experimental evidence to link the processes behind crystallization and actual stone growth. We have established a new technique of growing macroscopic calcium oxalate stones in vitro, based on the mixed suspension mixed product removal system, [12,13]. This model system (a stone farm) is ideal to test more directly the effects of citrate on residual fragments.…”

Kidney Stone Models for In Vitro Lithotripsy Research: A Comprehensive Review

“…9 Similarly, a technique was also described for generating calcium oxalate stones in-vitro by Ananth and colleagues (2002). 15 This method known as mixed-suspension, mixedproduct removal (MSMPR) continuous crystallizer allowed the group to grow calcium oxalate stones of significant size (~1 cm) in artificial urine over the course of 4-16 days. 15 This technique was expanded to allow for simultaneous growth of calcium oxalate phantoms.…”

“…15 This method known as mixed-suspension, mixedproduct removal (MSMPR) continuous crystallizer allowed the group to grow calcium oxalate stones of significant size (~1 cm) in artificial urine over the course of 4-16 days. 15 This technique was expanded to allow for simultaneous growth of calcium oxalate phantoms. 16 The selection of the appropriate stone model is the first step in designing an appropriate in vitro analysis of a lithotripter.…”