[Metabolic evaluation in urinary lithiasis. What is a reasonable level? 1: Theoretical approach].

Whereas the etiology of urinary calculi and their metabolic exploration should be known, it appears unreasonable to conduct exhaustive metabolic explorations in all patients, therapy being usually symptomatic and based on advice on hygiene and diet. However, etiologic diagnosis is essential in a small number of cases: those which could benefit from effective preventive and curative measures and for which morbidity is elevated: cystinuria, hyperparathyroidism, uric acid calculi, patients at high developmental risks. It is possible, by simple, low cost means to select 95% of these patients. After a theoretical study of the distribution and lithiasic etiology, a practical conduct is proposed which takes into account the cost-effective ratio.