Clinical guideline offers recommendations on reducing recurrent kidney stones

Drinking more fluid to increase urination may reduce the risk of recurrence of kidney stones, a clinical guideline recommended. Monotherapy with a thiazide diuretic, citrate, or allopurinol can be used if increasing fluid intake is not effective, the guideline also stated.

Researchers reviewed published literature from 1948 to March 2014 to create the evidence-based clinical guideline, which appeared in the Nov. 4 Annals of Internal Medicine.

Patients who have had kidney stones should increase their fluid intake throughout the day to achieve at least 2 liters of urine per day to prevent a recurrence, according to the guideline (weak recommendation, low-quality evidence). Low-quality evidence from 1 study showed that patients with calcium stones who achieved this fluid intake had less recurrence than the control group (12.1% vs. 27.0%; follow-up, 60 months). Another trial that examined radiographic stone recurrence in patients with calcium stones showed a nonstatistically significant decrease in recurrence in patients with increased fluid intake compared with no treatment (8.0% vs. 55.6%; follow-up, 24 to 36 months).

If increasing fluid intake doesn't work, patients can try monotherapy with a thiazide diuretic, citrate, or allopurinol to prevent recurrent kidney stones (weak recommendation, moderate-quality evidence), the guideline also stated. Moderate-quality evidence from 6 fair-quality, placebo-controlled trials of thiazide diuretic showed that the risk for composite stone recurrence was lower in patients who were treated with thiazide than in those who weren't (24.9% vs. 48.5%). No significant differences were found in the risk for recurrence based on thiazide type or dosage.

Moderate-quality evidence from 6 placebo-controlled trials of citrate monotherapy showed that composite stone recurrence was lower in patients treated with citrate than in controls (11.1% vs. 52.3%), regardless of which type of citrate was used. One fair-quality trial showed no difference between citrate and control groups in risk for radiographic stone recurrence.

Moderate-quality evidence from 4 placebo-controlled trials of allopurinol monotherapy showed a reduced risk for composite stone recurrence with allopurinol. Two trials showed that risk for recurrence was lower in patients treated with allopurinol than in those who received placebo (33.3% vs. 55.4%). One fair-quality study showed a reduction in symptomatic stone recurrence (10.3% vs. 29.0%), although it found no difference in recurrence of radiographic stones between the treatments.

Stone recurrence may also be prevented by reducing dietary oxalate, such as that found in chocolate, beets, nuts, rhubarb, spinach, strawberries, tea, and wheat bran; reducing dietary animal protein and purines; and maintaining normal dietary calcium, according to the guideline.

The evidence also showed that patients who decreased intake of soda that was acidified by phosphoric acid had reduced kidney stone recurrence. Low-quality evidence from 1 study showed that patients with baseline soft drink consumption of more than 160 mL per day who were instructed to abstain from drinking soda had a reduced risk for symptomatic stone recurrence compared with no treatment (33.7% vs. 40.6%). The benefit was limited to patients who drank soda that was acidified by phosphoric acid (typically colas) rather than those acidified by citric acid (typically fruit-flavored sodas).