Open Access
Urinary saturation and risk factors for calcium oxalate stone disease based on spot and 24-hour urine specimens
Yoshihide Ogawa1,Hiroyuki Yonou1,Sanehiro Hokama1,Masami Oda1,Makoto Morozumi1,Kimio Sugaya1
Department of Urology, Faculty of Medicine, University of the Ryukyus, Okinawa, Japan 903-0215.
DOI: 10.2741/1139 Volume 8 Issue 1, pp.167-176
Published: 01 September 2003
(This article belongs to the Special Issue Kidney stones; their formation, removal and prevention)

In 222 random spot urine specimens, the calcium concentration and calcium oxalate saturation [DG(CaOx)] were significantly higher among stone formers than among non-stone formers, while the citrate and creatinine-corrected citrate concentrations were lower. In 188 24-hour urine specimens, magnesium excretion was lower among stone formers than non-stone formers, while the creatinine-corrected calcium concentration and DG(CaOx) were higher. Among stone formers, there was no gender difference in the urinary concentrations of calcium, oxalate, citrate, magnesium, and DG(CaOx), but the creatinine-corrected calcium, citrate, and magnesium concentrations were higher in women, as well as 24-hour citrate excretion. The levels of calcium and oxalate have a major influence on DG(CaOx), while citrate and magnesium levels have a minor influence. DG(CaOx) was correlated with calcium and oxalate excretion, as well as with the creatinine-corrected calcium and oxalate concentrations. Approximately 5% of 24-hour urine specimens showed critical supersaturation, 80% showed metastable supersaturation, and 15% were unsaturated. Hypercalciuria or hyperoxaluria was fairly common (30% and 40%) in critically supersaturated urine, while it was less common (22.4% and 8.6%) in metastably supersaturated urine and was not detected in unsaturated urine. Hypocitraturia and/or hypomagnesiuria was more common (63.8-80%) at any saturation. The urinary calcium, oxalate, and citrate concentrations, as well as the creatinine-corrected calcium, oxalate, citrate, and magnesium concentrations and DG(CaOx), showed a significant correlation between 57 paired early morning spot urine and 24-hour urine specimens. The creatinine-corrected calcium and citrate concentrations of the early morning urine specimens were significantly correlated with the levels of calcium and citrate excretion in the paired 24-hour urine specimens. In conclusion, no parameter other than urinary saturation gives more than a vague indication of the risk of lithogenesis, so DG(CaOx) in either early morning urine or 24-hour urine specimens appears to be the best predictor of stone risk. Finally, the creatinine-corrected calcium and citrate concentrations in early morning urine can be used as a substitute for measuring 24-hour excretion.

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Yoshihide Ogawa, Hiroyuki Yonou, Sanehiro Hokama, Masami Oda, Makoto Morozumi, Kimio Sugaya. Urinary saturation and risk factors for calcium oxalate stone disease based on spot and 24-hour urine specimens. Frontiers in Bioscience-Landmark. 2003. 8(1); 167-176.