Study of Calcium Oxalate Crystalluria on Renal and Vesical Urines in Stone Formers and Normal Subjects

Abstract

Objective: The aim of this study is to compare vesical and renal calcium oxalate crystalluria in an attempt to correlate crystal formation with chemical composition and calcium oxalate saturation of renal urine. Material and Methods: Urine specimens were directly collected from the bladder and the kidney, of 11 stone formers and 11 control subjects under general anesthesia. The type of crystals present in urine as well as their size, number by cubic millimeter and state of aggregation were determined. In addition, calcium, magnesium, sodium, chloride, phosphate, citrate, oxalate, pyrophosphate and uric acid were measured in order to evaluate the calcium saturation status (EQUIL V program). Results: Calcium oxalate crystals were detected in 3 stone formers (27%) and 2 control subjects (18%) in vesical urine and in 4 stone formers (36%) and 3 control subjects (27%) in renal urine. Only 2 stone formers presented with simultaneous renal and vesical crystalluria. Subjects of the two groups with and without renal crystalluria were compared in terms of chemical composition and calcium oxalate saturation of renal urine. Crystalluric subjects (n = 7) had significantly higher uricosuria (p = 0.02), calciuria (p = 0.04), magnesiuria (p = 0.04) and calcium oxalate molar product (p = 0.05) than noncrystalluric (n = 15); calcium oxalate saturation was similar (p = 0.5). Conclusions: Beyond theorical considerations on lithogenesis, our observations and in particular the apparent discrepancy between renal and vesical crystalluria pose the problem of the clinical interest of the evaluation of calcium oxalate crystalluria based on freshly voided urine in the assessing the lithogenic risk or in the follow-up of patients who are particularly prone to stone recurrence.

Urinary oxalate excretion in urolithiasis and nephrocalcinosis

“…Although its predictive value is controversial in adult stone formers33and could not strictly be proven in this study, the data on urinary calcium oxalate saturation were helpful for the clinical guidance of HyOx children. If urinary calcium oxalate saturation was increased, suggesting at least partial non-compliance, patients were promptly advised to adhere more strictly to treatment consisting of high fluid intake, citrate administration and—except in PH1—dietary oxalate restriction 25…”

Urinary lithogenesis risk tests: Comparison of a commercial kit and a laboratory prototype test

“…Employing the same reasoning, crystalluria has been used as a simple method to evaluate lithiasis severity and the efficacies of various drugs [13][14][15]. However, the use of crystalluria as a diagnostic tool to evaluate renal lithiasis remains controversial; several reports have found no correlation between crystalluria and lithogenic urine, and Validity of test data when urine samples were lithogenic or non-lithogenic according to the criteria in Table II crystalluria was reported to be poorly predictive of recurrent stone formation [16][17][18]. These apparent discrepancies challenge the current clinical interest in evaluation of calcium oxalate crystalluria in freshly voided urine and question whether it reflects lithogenic risk.…”

Metabolic diagnosis and medical prevention of calcium nephrolithiasis and its systemic manifestations: a consensus statement

“…The type of CaOx crystals (whewellite vs. weddellite) seems to discriminate to a degree between hyperoxaluric and hypercalciuric stone formers [61]. Volume of crystals was higher in stone formers [62, 63]. However, crystal presence was not modified by different treatments even though the type of crystals changed from more calcium phosphate to more CaOx [60].…”