Classification of Stone-Patients and Healthy Persons on the Basis of the Urinary Analysis

Comment on Epitaxial Relationships between Uric Acid Crystals and Mineral Surfaces: A Factor in Urinary Stone Formation

“…In a recent study, Frincu et al, using the lattice matching program EpiCalc, demonstrated the existence of several lattice fits between various urate phases and several minerals commonly present in urinary calculi. On the basis of these findings, they have confirmed, as was originally suggested by Lonsdale and previously demonstrated experimentally by many others, − the theoretical possibility of the epitaxial growth of different stone minerals on urate nuclei. To make their suggestion physiologically pertinent to the genesis of urinary stones, the authors claimed that the effect holds true even in urine in vitro, citing in support of their statement two of our papers. , …”

“…17,18 We wish to point out that neither of those publications reported evidence demonstrating the epitaxial deposition of calcium oxalate (CaOx) onto urate seed crystals. In the first publication, 17 we showed that seed crystals of monosodium urate and uric acid do not promote CaOx deposition "to a physiologically significant" degree in human urine in vitro, which contradicted several previous papers reporting that sodium urate [3][4][5][6]8,12 and uric acid 7,9,10,12,[14][15][16] seed crystals induced the precipitation of CaOx from inorganic metastable solutions and questioned the physiological relevance of those findings. The contradiction prompted us to perform a second study 18 in which we preincubated sodium urate and uric acid seed crystals with urine to determine whether superficial coating with urinary components altered their ability to induce the deposition of CaOx from inorganic solutions.…”