<p><strong>In pediatric patients with calcium-based stones, clinicians should recommend sufficient fluid intake to produce a daily urine output of at least 30 mL/kg. (<em>Expert Opinion</em>) </strong></p>
Discussion
Discussion
<p>Higher urinary volume is a low-risk, foundational strategy to reduce urinary supersaturation of lithogenic solutes and thereby lower the risk of recurrence in pediatric patients with kidney stones. In pediatric patients who weigh <75 kg, a target urine output is ≥30 mL/kg/day which provides a weight-scaled stone-prevention goal derived from the adult target of at least 2.5 L/day; for example, a 74 kg adolescent would have a target urine output of 2,442 mL/day.<sup>128</sup> This target is intentionally higher than the normal urine output of 0.5-1 mL/kg/hour.<sup>129</sup> Thus, the ≥33 mL/kg/day target should be interpreted as a preventive strategy for pediatric stone formers. Observational data in adolescents with kidney stones showed a strong, quantifiable relationship between increased fluid intake and higher 24-hour urine volume. The additional fluid intake needed to produce the desired increase in urine output (dUOP) was additional fluid intake equal to dUOP/0.71. This study, which supports the practicality of “fluid prescriptions” to reach urine output goals, could help operationalize the necessary fluid intake to achieve urine output goals.<sup>130</sup></p>
<p>The PUSH trial provides contemporary randomized evidence relevant to this recommendation. In this multicenter trial of participants ≥12 years of age with urinary stone disease and low baseline urine volume, adolescents weighing <75 kg used the same target of ≥30 mL/kg/day, whereas adults and adolescents ≥75 kg used a fixed target of ≥2.5 L/day. The behavioral intervention increased 24-hour urine volume compared with guideline-concordant care, but did not reduce symptomatic stone recurrence over 2 years, indicating that the intervention was insufficient to improve clinical outcomes beyond usual care rather than that increased fluid intake is unimportant for prevention.<sup>127, 128</sup></p>