[Evaluation of renal stone disease: metabolic study]

Renal stone formation is a multifactorial process in which all the information obtained from the patient (medical history, imaging tests, stone analysis, metabolic study and physicochemical urine analysis) shows a different facet of the same process. Consequently, all these investigations should be evaluated together. In half of all patients, stone formation is secondary to the presence of metabolic alterations in urine, of which the most frequent is idiopathic hypercalciuria. The second most frequent cause is infection and/or urinary malformations, while hereditary enzyme defects are highly unusual. Reference values for urinary excretion of lithogenic metabolites (calciuria, uricosuria, oxaluria, citraturia, etc.) are essential for an adequate metabolic study, since urinary excretion depends on multiple factors, which have been described in the various publications in the literature. Physicochemical study evaluating saturation of the various salts dissolved in urine should be performed. These saturations are currently considered to be a highly useful index for determining the risk of crystallization and stone formation in patients with lithiasis and for evaluating the effectiveness of treatment. Lastly, the metabolic profile of renal lithiasis in children resembles that in adults, suggesting that predisposition to renal lithiasis begins in childhood. The early detection of the metabolic alterations observed in these patients will reduce the incidence of this disease in both children and adults.