Metabolic evaluation in stone patients in relation to extracorporeal shock wave lithotripsy treatment.

No information exists in the literature about the optimal time for metabolic evaluation of stone patients in relation to extracorporeal shock wave lithotripsy (ESWL) treatment. It is uncertain whether the presence of a stone, ESWL treatment itself or subsequent colic episodes influence the urinary risk factors. A prospective study was performed to determine the optimal period for metabolic evaluation. Two 24-hour urine samples were collected directly before, and 1 week, 1 month and 3 months after therapy in an outpatient setting and tested for total volume, calcium, uric acid, oxalate, citrate and creatinine levels. A total of 66 patients was available for evaluation. Comparison of the 4 subsequent collecting periods showed no statistically significant differences in the excretion values. Also, in subgroups of patients with colic (16%), on a calcium oxalate restricted diet (12%) and with repeated treatments within 3 months (33%) no differences were noted. This means that the presence of a stone, treatment itself or subsequent colic episodes have no adverse effect on the urinary risk factors. For practical reasons metabolic evaluation directly before ESWL treatment seems most attractive. In the pre-ESWL samples hypercalciuria (greater than 7.5 mmol./24 hours), hyperuricosuria (greater than 6 mmol./24 hours), hyperoxaluria (greater than 0.5 mmol./24 hours) and hypocitraturia (less than 2 mmol./24 hours) were found in 31%, 12%, 18% and 27%, respectively, of the patients. It is concluded that metabolic evaluation before ESWL is practical, applicable and reliable.