[Metabolic changes in 2612 patients with nephrolithiasis].

Nephrolithiasis is one of the most frequent pathologies of the urinary tract. Its prevalence in the city of Buenos Aires is 4%. Different biochemical and physiological disturbances may create an environment conductive to renal stone formation. We present the results of an ambulatory evaluation in 2612 patients for the purpose of updating the classification of nephrolithiasis. An abnormal urinary biochemistry was observed in 2423 patients (92.8%) that could be classified in 15 categories. A single diagnosis was documented in 61.5% of the patients, and the remaining 31.2% had more than one diagnosis (concurrent abnormalities). No abnormality was found in 189 stone formers (7.2%). Idiopathic hypercalciuria was the most frequent abnormality, it was encountered in 31.2%; hyperuricosuria and gouty diathesis (presence of urine pH < 5.5, with normal or high uricemia) accounted for 9.4% and 5.4% of patients, respectively. On the other hand, hypomagnesuria affected 6.7% of the stone formers and hypocitraturia was observed in 4.5%. Primary hyperparathiriodism, hyperoxaluria and cystinuria were seen less frequently in 2.6%, 1.3 and 0.45% of patients. Low urine volume was found in 12% of the patients. Among those patients with more than one abnormality, we found that hypercalciuria together with hyperuricosuria and hypocitraturia (12%) was the prevalent association followed by hypercalciuria with hyperuricosuria (9.1%). Our results show the importance of studying nephrolithiasis patients from a biochemical point of view, since this is the only way to achieve a diagnosis of the metabolic abnormality and introduce a specific therapy to prevent recurrence.