In adults with recurrent calcium oxalate or calcium phosphate stones, increased fluid intake, a normal- to high-calcium diet lower in protein and sodium, and some pharmacologic therapies may help reduce recurrence or stone growth, according to a systematic review published in Annals of Internal Medicine. However, the evidence was mostly low strength, most studies had important limitations, pediatric data were sparse, and the review identified no eligible studies evaluating surveillance imaging strategies. Most included studies were rated as having high or serious risk of bias.
Kidney stones are common and often recur. Adults face an approximately 25% risk for recurrence within 5 years after a first stone, while those with prior stones have about a 50% risk for recurrence.
Among dietary interventions, one randomized controlled trial provided low-strength evidence that advising patients to increase fluid intake to achieve a urine volume of at least 2 L/day reduced composite stone recurrence compared with no treatment in patients with calcium oxalate or phosphate stones.
Another trial provided low-strength evidence that a diet with normal to high calcium and lower protein and sodium reduced recurrence compared with a low-calcium diet in men with idiopathic hypercalciuria and recurrent calcium oxalate stones.
Evidence for other dietary strategies was insufficient or inconsistent. The review found insufficient evidence for interventions such as reduced soft drink intake, low-mineral water, low-protein diets combined with other dietary changes, and low-oxalate diets.
The review also evaluated pharmacologic therapies. In adults, thiazides, alkali therapy, and allopurinol each had low-strength evidence of at least a small benefit for at least one recurrence-related outcome, although evidence for symptomatic recurrence was often insufficient. Confidence in the magnitude of benefit is limited given the overall risk of bias in the included studies.
For alkali therapy, citrate salts and lemon juice were associated with possible benefit for composite recurrence or growth in some studies, although lemon juice was linked to more minor adverse events. Allopurinol showed possible benefit in adults with predominantly calcium oxalate stones. Acetohydroxamic acid showed possible benefit only in patients with infection-related stones and was associated with increased adverse events.
The review found low-strength evidence of little or no difference between selective and empiric pharmacotherapy based on 24-hour urine testing, and insufficient evidence to support metabolically tailored dietary interventions based on such testing.
The researchers highlighted several gaps in the evidence base, including limited data in pediatric patients, lack of evidence on surveillance imaging strategies, and the need for future studies focused on specific stone subtypes, adherence strategies, and patient-centered outcomes.
Overall, the findings suggest that increased fluid intake, targeted dietary modification, and selected pharmacologic therapies may help reduce recurrence or stone growth in adults with calcium-based stones, but the evidence remains limited and should be interpreted cautiously.
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Source: Annals of Internal Medicine
