Carvalho M, Vieira MA. Changes in calcium oxalate crystal morphology as a function of supersaturation.
Int Braz J Urol 2005;
30:205-8; discussion 209. [PMID:
15689248 DOI:
10.1590/s1677-55382004000300005]
[Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2004] [Accepted: 05/10/2004] [Indexed: 11/22/2022] Open
Abstract
PURPOSE
To study the changes in calcium oxalate crystal morphology induced by different levels of supersaturation (SS) in human urine.
MATERIALS AND METHODS
Twenty-four hours urine samples from 5 normal men were collected. Each specimen was centrifuged and filtered. About 200 mL of each sample was dialyzed overnight. Aliquots of 2 mL of urine was then added to a 24-wells tissue culture plate and checked for crystal absence. Calcium oxalate crystals were precipitated from each sample by adding sodium oxalate and calcium chloride in sufficient quantities to induce spontaneous crystallization. Finally, each plate hole was examined with an inverted polarized microscope (X500 magnification). Initial SS of each sample relative to calcium oxalate was calculated using an iterative computer program.
RESULTS
Crystal formation was connected to relative calcium oxalate (CaOx) SS. At SS of 10, small crystals of similar shape were formed, mainly CaOx dihydrate morphology. At SS of 30, there was an enormous increase in the number of crystals, that kept the same size. SS greater than 50 produced larger crystals with different shapes and multiple crystalline aggregates. Urine was able to tolerate, i.e., to avoid crystal formation, until SS ratios of approximately 10.
CONCLUSIONS
Relative CaOx SS and the concentration ratio of calcium to oxalate are important determinanting factors of crystal morphology. Non-dialyzable urinary proteins can act as inhibitors and influence the structure of formed crystals. Additional studies from patients with kidney stones are needed in order to establish whether crystal size and habit distribution are different from crystals in normal urine.
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