Whitlockite structures in kidney stones indicate infectious origin: a scanning electron microscopy and Synchrotron Radiation investigation

Evidence of bacterial imprints in different types of non-struvite kidney stones

BACKGROUND

Recent studies of renal lithiasis identified bacterial imprints in apatite phosphate stones and mixed calcium oxalate/apatite phosphate stones, neither of which contained struvite.

METHODS

This cross-sectional observational study examined 903 stones that were collected from 844 patients during the course of 1 year. All stones were initially examined by stereoscopic microscopy. Stone fragments were then examined by scanning electron microscopy + microanalysis by X-ray dispersive energy and by Fourier-transform infrared spectroscopy. When bacterial imprints were detected, biochemical and bacteriological analysis of the patient's urine was performed.

RESULTS

We found 8 renal stones that had bacterial imprints but no struvite. All 8 stones contained hydroxyapatite, and the imprints were located in this region. Five stones contained hydroxyapatite as the major component, two stones were mixed hydroxyapatite/calcium oxalate dihydrate stones, one was a papillary calcium oxalate monohydrate stone in which bacterial imprints were located at Randall's plaque and the other was a cavity calcium oxalate monohydrate stone that contained hydroxyapatite in the central core with bacterial imprints.

CONCLUSION

We identified bacterial imprints in different types of renal stones that lacked struvite, including papillary stones, and these imprints were always present in a hydroxyapatite matrix. Notably, a urinary pH above 6.0 favors the formation of apatite phosphates and the growth of bacteria. Our findings point to the importance of controlling urinary pH to prevent bacteria-mediated calculogenic processes.

CLINICAL TRIAL NUMBER

Not applicable.

Understanding the role of zinc ions on struvite nucleation and growth in the context of infection urinary stones

Taking into account that in recent decades there has been an increase in the incidence of urinary stones, especially in highly developed countries, from a wide range of potentially harmful substances commonly available in such countries, we chose zinc for the research presented in this article, which is classified by some sources as a heavy metal. In this article, we present the results of research on the influence of Zn2+ ion on the nucleation and growth of struvite crystals-the main component of infection urinary stones. The tests were carried out in an artificial urine environment with and without the presence of Proteus mirabilis bacteria. In the latter case, the activity of bacterial urease was simulated chemically, by systematic addition of an aqueous ammonia solution. The obtained results indicate that Zn2+ ions compete with Mg2+ ions, which leads to the gradual replacement of Mg2+ ions in the struvite crystal lattice with Zn2+ ions to some extent. This means co-precipitation of Mg-struvite (MgNH4PO4·6H2O) and Znx-struvite (Mg1-xZnxNH4PO4·6H2O). Speciation analysis of chemical complexes showed that Znx-struvite precipitates at slightly lower pH values than Mg-struvite. This means that Zn2+ ions shift the nucleation point of crystalline solids towards a lower pH. Additionally, the conducted research shows that Zn2+ ions, in the range of tested concentrations, do not have a toxic effect on bacteria; on the contrary, it has a positive effect on cellular metabolism, enabling bacteria to develop better. It means that Zn2+ ions in artificial urine, in vitro, slightly increase the risk of developing infection urinary stones.

Antioxidant and Anti-Urolithiatic Activity of Aqueous and Ethanolic Extracts from Saussurea costus (Falc) Lispich Using Scanning Electron Microscopy

The plant Saussurea costus (Falc) Lipsch has many biological activities and a strong curative and preventive power against a variety of diseases including cancer, diabetes, and hemorrhoids. In the current study, phytochemical screening was carried out as well as an investigation of the antilithiatic and antioxidant activities of aqueous and ethanolic extracts of this plant. The results showed that aqueous and ethanolic extracts were effective in reducing cystine stone mass and that the aqueous extract of Saussurea costus (Falc) Lipsch had the highest percentage of dissolution (6.756 ± 1.024) (p < 0.05). A turbidimetric method and a crystallization test were used to evaluate the antilithiatic activity of an aqueous and ethanolic extract of this plant on calcium oxalate crystallization. The results of these methods revealed that the ethanolic extract of this plant has a significant inhibitory effect on calcium oxalate crystallization, with a percentage inhibition of (91.017 ± 0.299) (p < 0.05) for a concentration of 2 mg mL−1. The DPPH method revealed that the ethanolic extract of Saussurea costus (Falc) Lipsch with a concentration of (IC50 = 0.12325 mg mL−1) had the highest IC50, whereas the FRAP method revealed that the aqueous extract of Saussurea costus (Falc) Lipsch with a concentration of 300 µg mL−1 has the most significant reducing power with (OD = 0.56 ± 0.05). These findings indicate that aqueous and ethanolic extracts of Saussurea costus (Falc) Lipsch had a significant effect on whewellite and weddellite and a greater free radical scavenging effect but had no effect on cystine dissolution.