Metabolic Work-up of Patients with Urolithiasis: Indications and Diagnostic Algorithm.

CONTEXT: The incidence of urinary tract stone disease is increasing and the risk of recurrent stone formation is high. Appropriate therapeutic procedures with the aim of counteracting the progress of stone formation are highly desirable. Metabolic work-up is considered essential as a base for optimal design and follow-up of effective recurrence prevention.

OBJECTIVE: To scrutinize the current literature with regard to principles of metabolic work-up for this heterogeneous group of patients.

EVIDENCE ACQUISITION: Relevant articles in PubMed, guideline documents, consensus reports, and the Cochrane Library published during the past 20 yr were consulted.

EVIDENCE SYNTHESIS: Grades of recommendation were used according to the principles applied in the European Association of Urology and American Urological Association guidelines. Medical efforts to prevent recurrent stone formation should be part of the care of patients with urinary tract stone disease (grade of recommendation A). A careful medical history and imaging together with analysis of stone composition, blood, and urine provide the basis for appropriate measures, but the treatment has to be individualized (grade of recommendation D). Whenever possible, stone analysis should be carried out at least once for every patient or each time when a long time has elapsed between two stone episodes because the risk factors explaining stone formation may have changed (clinical principle). The medical history, including information on dietary and drinking habits as well as lifestyle, is necessary for appropriate advice (grade of recommendation C). The medical history, together with imaging and stone composition, is used to estimate the severity of the disease (clinical principle). Identification of specific medical conditions should be supported by blood and/or urine analysis (grade of recommendation B). Pharmacological agents associated with an increased risk of stone formation should be identified (grade of recommendation C). Patients who have formed noncalcium stones should always be given recurrence preventive treatment. Analysis of urine composition for these patients is optional, but might be of value in the follow-up to support decisions on appropriate dosage regimens (grade of recommendation C). For patients with idiopathic calcium stone disease information from 24-h urine samples should be used, although the number of samples to be taken is debated (grade of recommendation C). Information from 24-h urine analysis should be used for selective dietary and drinking advice as well as for selection of the most appropriate pharmacological agent (grade of recommendation B). The treatment effects on the risk of stone formation can be followed by estimates of supersaturation based on urine composition (grade of recommendation C).

CONCLUSIONS: It is clear that the metabolic work-up of patients with urinary tract stone disease should be individualized according to stone type and severity of the disease, and that the different therapeutic approaches are closely associated with the availability of therapeutic tools and motivation by the patient.

PATIENT SUMMARY: Effective prevention of recurrent stone formation is determined by several factors such as the current and previous stone episodes and surgical procedures, stone composition, medical history, dietary and drinking habits, lifestyle, and ongoing pharmacological therapy. Analysis of blood and urine is an important part of the metabolic evaluation, but how extensive the risk evaluation should be is determined by the type of stone and the severity of the disease.