Urine osmolality predicts calcium-oxalate crystallization risk in patients with recurrent urolithiasis

Stavros A. Kavouras, Hyun Gyu Suh, Marion Vallet, Michel Daudon, Andy Mauromoustakos, Mariacristina Vecchio, Ivan Tack

Research output: Contribution to journalArticlepeer-review

Abstract

Our aim was to investigate the validity of osmolality from 24-h urine collection in examining the risk for calcium-oxalate (CaOx) kidney stone formation in patients with recurrent urolithiasis. Three hundred and twelve subjects (males/females: 184/128) from France with a history of recurrent kidney stones from confirmed or putative CaOx origin were retrospectively included in the study (46 ± 14 years, BMI: 25.3 ± 5.0 kg·m−2). Tiselius’ crystallization risk index (CRI) was calculated based on urinary calcium, oxalate, citrate, magnesium, and volume from 24-h samples. The diagnostic ability of 24-h urine osmolality to classify patients as high risk for kidney stone crystallization was examined through the receivers operating characteristics analysis. High risk for CaOx crystallization was defined as CRI > 1.61 and > 1.18, for males and females, respectively. The accuracy of urine osmolality to diagnose risk of CaOx stone formation (AUC, area under the curve) for females was 84.6%, with cut-off point of 501 mmol·kg−1 (sensitivity: 83.3%, specificity: 76.0%). Males had AUC of 85.8% with threshold of 577 mmo·kg−1 (sensitivity: 85.5%, specificity: 77.6%). A negative association was found between 24-h urine volume and osmolality (r = − 0.63, P < 0.001). Also, a positive association was found between 24-h urine osmolality and CRI (r = 0.65, P < 0.001), as well as urea excretion with CRI (r = 0.37, P < 0.001). In conclusion, urine osmolality > 501 and > 577 mmol·kg−1, in female and in male, respectively, was associated with a risk for CaOx kidney stone formation in patients with a history of recurrent urolithiasis. Thus, when CaOx origin is confirmed or suspected, 24-h urine osmolality provides a simple way to define individualized target of urine dilution to prevent urine crystallization and stone formation.

Original languageEnglish (US)
Pages (from-to)399-405
Number of pages7
JournalUrolithiasis
Volume49
Issue number5
DOIs
StatePublished - Oct 2021

Keywords

  • Calcium
  • Crystallization
  • Kidney stones
  • Oxalate
  • Urine volume

ASJC Scopus subject areas

  • Urology

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