[Indicators of the risk of calcium oxalate urinary calculi: comparative study of the Parks' and Tiselius' indices, urinary citrate/calciuria ratio, and morning crystalluria].

Despite the progress in basic research, the precise assessment of the risk of calcium oxalate urinary stones and the detection of patients at particular risk of recurrent stones are often problematical. A population of 55 renal stone patients and 50 controls served as a basis for various comparative studies of Parks' index, Tiselius' index, the urinary citrate/urinary calcium ratio and the morning calcium oxalate crystalluria. Parks' index and the urinary citrate/urinary calcium ratio were highly discriminant, in contrast with Tiselius' index and crystalluria, which were statistically comparable in the 2 groups. A close correlation was observed for the 3 versions of Tiselius' index, which estimates diuresis, but no particular correlation was detected between crystalluria and the other parameters studied. Parks' index and the urinary citrate/urinary calcium ratio are potentially adapted to the detection and monitoring of renal stone patients at risk of recurrence. On the other hand, the various Tiselius' indices can be essentially used to evaluate urinary calcium oxalate oversaturation and possibly to control treatments interfering with this parameter. The formula simply based on diuresis, and the 24-hour urinary calcium and oxalate excretion (CaO.71.Ox.V-1.2) appears to be sufficient for this purpose. The absence of correlation between crystalluria and the other potential indicators of lithogenic risk raises the problem of their respective validity as well as the possible prevalence in the crystallization process of the powerful inhibitors which are currently unidentified, but probably macromolecular.