[Circadian rhythms of lithogenic and inhibitory substances in the urine]

The diurnal variations of urine composition with respect to urinary pH, volume, creatinine, calcium, magnesium, phosphate, uric acid, citrate and oxalate were studied in five healthy men. Generally, there was considerable variations in the excretion of the different urine constituents with meal related peaks except phosphate, which was most pronounced after dinner. The analysis of a 24-hour urine collection cannot account fully for the crystallization properties of urine and a fractionated urinalysis might be of value for therapeutic decisions. However, such procedures probably will not be possible in clinical practice and more reliable methods for evaluation of the crystallization propensity in whole 24-hour urine have to be developed.