Idiopathic calcium oxalate urinary lithiasis: usefulness of Parks' and Tiselius' indices in the evaluation of the risk of stone formation.

Different indices of the risk of urinary calcium oxalate crystallization were compared to determine their usefulness in detecting the stone-formers particularly prone to recurrence. Urine volume and calcium, oxalate, citrate, magnesium or creatinine were determined in 55 patients presenting with an idiopathic calcium oxalate urolithiasis, as well as in 50 control subjects. On 24-hour urine samples, these elements allowed for the calculation and comparison of different indices of lithogenous risk as proposed by Parks and Tiselius. Both Parks' indices and the urinary citrate-calcium ratio varied significantly between the two groups, but conversely Tiselius' indices were statistically comparable. The three Tiselius' indices taking the 24-hour urine volume into account were also strongly correlated. Parks' index and the urinary citrate-calcium ratio are highly discriminating and potentially relevant to select the stone-formers with a high risk of relapse. Tiselius' indices basically reflect urinary calcium oxalate saturation, and can only be used clinically to control the treatment interfering with this. In this respect, the formula based simply on urine volume, calcium and oxalate over 24 h (Ca0.71.Ox.V-1.2) appears to be sufficient.

Circadian variations in the risk of urinary calcium oxalate stone formation.

OBJECTIVE: To evaluate the circadian fluctuations in the risk of urinary calcium oxalate stone formation with regard to critical periods of crystallization. PATIENTS AND METHODS: Over a given time period, the Tiselius index depends on urine volume and urinary excretion of oxalate, calcium, citrate and magnesium. This crystallization potential was evaluated during three successive periods spread over 24 h for 25 recurrent stone-formers aged 16-76 years (mean 50) and 25 control subjects aged 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 afternoon and the circadian pattern of the index illustrated the predominant importance of urinary output in its determination. Morning urinary concentrations and excretions of citrate, and nocturnal levels of magnesium were significantly higher in the stone-formers when compared with the control subjects. CONCLUSION: The lithogenic risk for calcium oxalate stones was maximal at the end of the night or during the early morning, when urinary output was minimal. This circadian study revealed abnormalities that are not apparent from non-fractionated 24 h urine samples, and which were potentially relevant to therapy.