Basic Study
Copyright ©The Author(s) 2017. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Urol. Jul 24, 2017; 6(2): 40-43
Published online Jul 24, 2017. doi: 10.5410/wjcu.v6.i2.40
Urinary supersaturation as a diagnostic measure in urolithiasis
Otakar Söhnel, Felix Grases
Otakar Söhnel, Faculty of Environmental Studies, University of J.E. Purkyně, 40096 Ústí n.L., Czech Republic
Felix Grases, Laboratory of Renal Lithiasis Research, University Institute of Health Sciences Research, University of Balearic Islands, 07122 Palma of Mallorca, Spain
Author contributions: Söhnel O and Grases F contributed to the conception and development of the theoretical aspects that have led to the conclusions reached; both authors approved the final version of the article to be published.
Institutional review board statement: Not applicable.
Institutional animal care and use committee statement: Not applicable.
Conflict-of-interest statement: The authors declare no conflict of interest.
Data sharing statement: Not applicable.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Felix Grases, PhD, Professor, Director of the Laboratory of Renal Lithiasis Research, Director of the University Institute of Health Sciences Research, Laboratory of Renal Lithiasis Research, University Institute of Health Sciences Research, University of Balearic Islands, Carretera Valldemossa Km 7.5, 07122 Palma of Mallorca, Spain. fgrases@uib.es
Telephone: +34-971-173257 Fax: +34-971-259935
Received: November 9, 2016
Peer-review started: November 10, 2016
First decision: February 16, 2017
Revised: February 26, 2017
Accepted: March 13, 2017
Article in press: March 13, 2017
Published online: July 24, 2017
Processing time: 254 Days and 2.9 Hours
Abstract
AIM

To demonstrate that urinary supersaturation per se is not a reliable diagnostic measure of the risk for stone formation.

METHODS

Available physical and chemical data for calcium oxalate monohydrate (COM) and calcium hydrogen phosphate dihydrate (brushite, BRU), and urinary supersaturations with respect to COM and BRU in healthy individuals and stone formers, were obtained from the literature. Classical theory of nucleation was used for calculations.

RESULTS

It was found that the rate of homogeneous nucleation (unaided by substrates) of COM and BRU is nil at all conceivable supersaturations of urine. Consequently spontaneous formation of crystals in urine requires the presence of nucleation substrates for (heteronuclei).

CONCLUSION

Urinary supersaturation with respect to lithiatic compounds is a necessary, but not a sufficient condition for nephrolithiasis. The absence of crystallization inhibitors and the presence of efficient nucleation promoters (heteronuclei) in urine are further necessary conditions of urolithiasis occurrence. Urinary supersaturation per se is not a reliable diagnostic measure of the risk of kidney stone formation.

Keywords: Urinary supersaturation, Heterogeneous nucleation, Urolithiasis

Core tip: The supersaturation of urinary compounds has been considered during long time as a key risk factor for renal lithiasis. Nevertheless, theoretical studies demonstrate that the rate of spontaneous (homogeneous) nucleation of calcium oxalate monohydrate and brushite only occurs at urinary supersaturations much higher than conceivable in any individual. This demonstrates the necessity of presence of efficient substances or foreign solid particles for induced nucleation (heterogeneous) of lithiatic compounds. Consequently, urinary supersaturation per se is necessary but not sufficient condition for stone development. Fundamental condition of renal stone formation and development is presence of heteronuclei and significantly reduced content of crystal growth inhibitors. Identification of nucleation promoters and absence of crystal growth inhibitors is very important as a diagnostic aspect to avoid urolithiasis.