CIRCADIAN VARIATIONS IN THE RISK OF URINARY CALCIUM-OXALATE STONE FORMATION

Objective To evaluate the circadian fluctuations in the risk of urinar y calcium oxalate Stone formation with regard to critical periods of c rystallization. Patients and methods Over a given time period, the Tis elius index depends on urine volume and urinary excretion of oxalate, calcium, citrate and magnesium. This crystallization potential was eva luated during three successive periods spread oner 24 h for 25 recurre nt stone-formers aged 16-76 years (mean 50) and 25 control subjects ag ed 27-71 years (mean 44). Results There was no significant difference in the value of the Tiselius index for all equivalent time periods in both groups of patients. The minimum value was recorded in the afterno on and the circadian pattern of the index illustrated the predominant importance of urinary output in its determination. Morning urinary con centrations and excretions of citrate, and nocturnal levels of magnesi um were significantly higher in the stone-formers when compared with t he control subjects. Conclusion The lithogenic risk for calcium oxalat e stones was maximal at the end of the night or during the early morni ng, when urinary output was minimal. This circadian study revealed abn ormalities that are not apparent from non-fractionated 24 h urine and which were potentially relevant to therapy.