Metabolic investigations: When and in whom

Abstract

There is little outcome-based evidence to guide the metabolic evaluation of stone formers. The existing guidelines are based on the experience and rational thought processes of investigators of stone disease. That stones are highly recurrent is always stressed in offering a rationale for diagnostic evaluation and preventive therapy. Recurrence affects about 30% of patients at 5 years, 50% at 10 years, and 80% at 20 years. Yet even these significant recurrence rates may fail to motivate patients to adhere to lifelong regimens of fluid intake, dietary modification, or medical therapy. Large stones, consequential stones requiring urologic intervention, stones complicated by comorbidities such as heart disease, diabetes, and concomitant urinary tract infections may warrant evaluation and prevention even if they are "first" kidney stones. History taking should focus on activities, diet, occupation, medications, and family history. Twenty-four hour urine collections offer rich data regarding the etiology of stones and provide insight into patients' metabolism, diet, and habits and allow both dietary and medical therapy to be prescribed based on the individual's own pathophysiology. Follow-up collections allow the practitioner to determine the effect of therapy and consider further dietary recommendations or changes in medication dosages. Characterizing the cause of hypercalciuria has not been demonstrated to favorably affect the rationale for treatment and has not been tested regarding its ability to produce improved outcomes. It is relatively expensive, time consuming, and inconvenient and is therefore not recommended. © 2011 Springer-Verlag London Limited.