<p><strong>In adult patients with recurrent kidney stones of unknown composition, clinicians may offer empiric preventative pharmacotherapy (e.g., thiazide diuretics, alkali, allopurinol) in the absence of urine chemistry. <em>(Conditional Recommendation; Evidence Level: Grade C) </em></strong></p>
Discussion
Discussion
<p>Empiric preventative pharmacological therapy refers to the use of pharmacologic agents to reduce the risk of stone recurrence in the absence of stone composition and 24-hour urine chemistry to guide the choice of agent.<sup>235</sup> Many considerations support the use of empiric therapy including frequent absence of stone analysis due to uncollected stone(s) and limited availability, inconvenience, or difficulty in collecting a 24-hour urine (e.g., due to significant urinary incontinence). Additionally, the efficacy of many pharmacological agents in reducing stone recurrence may be independent of pre-treatment urine chemistry (e.g., efficacy of thiazide diuretics irrespective of urinary calcium excretion<sup>54</sup> and efficacy of alkali citrate irrespective of urinary citrate excretion<sup>32</sup>). In a single retrospective non-randomized study comparing empiric therapy with thiazides (used in 59% of patients), alkali citrate (used in 27%), and/or allopurinol (used in 21%) versus 24-hour urine-guided therapy with the same agents, there was no significant difference in the composite claims-based outcome for symptomatic stone events (i.e., emergency department visits, hospitalization, stone-directed surgery).<sup>67</sup> While stone analysis was not available in that study, the vast majority of stones are statistically likely to have been composed of calcium. As such, when metabolic testing is impractical or unwanted, clinicians may choose to initiate empiric therapy in patients with recurrent kidney stones in addition to recommending sufficient fluid intake to maintain a 24-hour urine volume of at least 2.5 L/day.</p>