Urolithiasis: Update on Metabolic Evaluation of Stone Formers

Metabolic abnormalities are identified in over 90% of stone formers and the institution of preventative dietary and medical measures has resulted in substantial reduction in stone recurrence rates. We review the contemporary approach to metabolic evaluation of urolithiasis. A careful medical and dietary history, stone analysis, serologic tests, and urinalysis constitute the initial screening regimen in patients who have been diagnosed with stones. Risk stratification of patients, based on the outcome of the initial screening tests, determines the need for and extent of urinary evaluation in individual stone formers. Conservative dietary measures or a simple metabolic evaluation and treatment has been described for first-time or low-risk stone formers, although the number of 24-h urine collections needed is debatable. A more extensive metabolic evaluation is recommended for recurrent or high-risk stone formers or for those in whom empiric treatment or medical therapy based on simplified evaluation is unsuccessful. Regardless of etiology, all stone formers should be counseled on dietary measures for stone prevention. The need for medication is determined by the results of 24-h urine analysis and the risk level of the patient. Cost effectiveness of the metabolic evaluation and treatment is strongly influenced by recurrence rate and efficacy of therapy. Metabolic evaluation and treatment has clearly been shown in randomized trials to reduce stone recurrence rates. Further study will determine the extent of evaluation necessary and the need for selective vs. empiric medical therapy for first-time and recurrent stone formers.