[Metabolic assessment of urinary lithiasis in routine practice. Common task of nephrologists and urologists of the Lithiasis Committee of the French Association of Urology].

Renal lithiasis is a frequent disease which recurs in more than 60% of cases. Effective prevention of recurrence can be obtained once the cause has been identified. The laboratory investigation, based on clinical history, analysis of the stone and blood and urine assays, achieves this objective. As the stone is the main indicator of lithogenic disorders, the investigation must start by morphoconstitutional analysis of the stone by reliable physical methods. The results of this analysis guide the clinician towards the biochemical factors responsible for the lithogenic process and, in some cases, directly to certain infectious diseases, such as infections due to urease-positive bacteria, or metabolic diseases, such as primary hyperoxaluria, tubular acidosis or enzymatic deficits of purine metabolism, without forgetting drug causes, responsible for the formation of approximately one per cent of stones. Subsequent investigations guided by analysis of the stone are therefore much more selective and rational. When the stone is not available, the investigation, graduated according to the metabolic activity of the lithiasis, can be guided by its radiological appearance. Dynamic investigations are rarely necessary and must be reserved a second-line procedures for the most severe forms of calcium-dependent stones. In the absence of radiological data and when the stone has not been collected, a basic routine blood and urine investigation must be performed looking for laboratory factors potentially involved in the stone-forming process.