Variations in Urine Composition During the Day in Patients With Calcium Oxalate Stone Disease

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Abstract
The diurnal variations of urine composition with respect to Ca Mg, oxalate, citrate and inhibition of calcium oxalate crystal growth were studied in patients with recurrent calcium oxalate stone disease. There was considerable variation in the excretion of the different urine constituents with meal-related peaks, which was most pronounced for Ca. The highest concentration of Ca was observed before noon, and between 1900-2300 h. Oxalate concentration was highest between 0600-1000 h. The highest levels of supersaturation were recorded between 0600-1000 h, and 1800-2200 h. The inhibition index was at the highest level during the first morning hours and could be important in counteracting crystal growth at that time. The risk of exceeding a theoretical formation product of calcium oxalate appeared to be low, with a 24-h urine volume > 2000 ml.