Value of repeated analyses of 24-hour urine in recurrent calcium urolithiasis

The value of repeated analyses of 24-hour urine collections for daily excretion of calcium, uric acid, citrate, phosphorus, and creatinine and for volume and pH performed to detect and classify metabolic disorders in a selected group of calcium stone formers with striking recurrence rates was assessed in a retrospective study.

A total of 441 urinalyses made over a mean period of 80.4 months of samples obtained from 49 patients were reviewed. Fifty-nine percent of patients were initially found to have metabolic disorders (absorptive hypercalciuria types I and II, hyperuricuria, hypocitraturia) and therefore received specific drug therapy (allopurinol, thiazide, alkali citrate, orthophosphate) for a mean of 45.7 months (group I). The remaining patients were classified as metabolically inactive and were given general metaphylactic instructions (group II).

In 73% of patients recurrent stones developed, with no statistically significant difference between the two groups (79% vs 65%). In 55% of group I patients, urinalyses continued to yield abnormal findings during follow-up; however, subsequent abnormal findings were also seen in 40% of the metabolically inactive group II patients. Overall, metabolic disorders were observed at some point in 75% of patients. Only 27% remained recurrence free, and 62% thereof also had pathologic urinary findings.

It does not appear that drug treatment in recurrent calcium urolithiasis based on urinary findings is superior to simple general metaphylactic recommendations, nor that repeated analyses of 24-hour urine collections furnish additional information on the risk of recurrent stone formation or on the presence of risk factors leading to recurrence in the long-term course of disease.