Chemolysis of calcium oxalate stones: study in vitro and possible clinical application

Preliminary Data on Geochemical Characteristics of Major and Trace Elements in Typical Biominerals: From the Perspective of Human Kidney Stones

The chemical composition of biominerals is essential for understanding biomineral formation and is regarded as an attractive subject in bio-mineralogical research on human kidney stones (urinary calculi). In order to obtain more geochemically interpreted data on biogenic minerals, mineralogical compositions and major and trace element concentrations of sixty-six kidney stone samples derived from kidney stone removal surgeries were measured. Infrared spectroscopy results showed that calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) were the two main mineral components of kidney stones. Geochemical results indicated that major and trace element concentrations were present in the following order: Ca > Mg > Na > K > Zn > Fe > Pb > Ba > Cu > Ti > Mo > Cd > Cr. With the exception of Ca, Mg was the second-most abundant element. Zn exhibited higher concentrations relative to other trace elements, which suggests a potential substitution of calcium by metal ions with a similar charge and radius rather than by metals in kidney stone formation. Pb appeared in significantly higher concentrations than in previous studies, which indicates Pb enrichment in the environment. In order to discern multi-element relationships within kidney stones, principal component analysis was applied. Three principal components (PCs, eigenvalues >1) were extracted to explain 64.4% of the total variance. The first component exhibited positively correlated Na-Zn-Cr-Mo-Cd-Pb, while the second component exhibited more positively weighted Mg-K-Ba-Ti. Fe-Cu demonstrated a positive correlation in the third component. This study suggests that Ca exhibits a preference for uptake by oxalates during human urinary stone crystallization, while other alkali metals and alkaline earth metals precipitate with phosphate.

Do organic substances act as a degradable binding matrix in calcium oxalate kidney stones?

BACKGROUND

Calcium oxalate (CaOx) stones are considered to be highly resistant to chemolysis. While significant organic matter has been identified within these stones, which is presumed to bind (inorganic) CaOx particles and aggregates, most chemolysis efforts have focused on methods to attack the CaOx components of a stone. We examine the feasibility of inducing chemolysis of CaOx kidney stones, within hours, by specifically attacking the organic matrix present in these stones.

METHODS

In contrast to previous studies, we focused on the possible "brick and mortar" stone configuration. We systematically tested, via in vitro experiments, the ability of an extensive range of 26 potential chemolysis agents to induce relatively fast disintegration (and/or dissolution) of a large set of natural CaOx stone fragments, extracted during endourological procedures, without regard to immediate clinical application. Each stone fragment was monitored for reduction in weight and other changes over 72 h.

RESULTS

We find that agents known to attack organic material have little, if any, effect on stone chemolysis. Similarly, protein and enzymatic agents, and oral additive medical treatments, have little immediate effect.

CONCLUSIONS

These findings suggest that the organic and inorganic constituents present in CaOx stones are not structured as "brick and mortar" configurations in terms of inorganic and organic components.

Evaluation of the effect of Moringa peregrina bark on the crystal habit and size of calcium oxalate monohydrate crystals in different stages of crystallization using experimental and theoretical methods

Moringa peregrina bark extract is found to successfully retard the nucleation and aggregation of calcium oxalate monohydrate crystals and distort their shape, a mechanism for which is proposed using molecular modeling.