A randomized, controlled trial of lactic acid bacteria for idiopathic hyperoxaluria.

BACKGROUND Urinary oxalate excretion is an important contributor to calcium oxalate stone formation. Methods of reducing oxalate excretion are not wholly satisfactory, and no controlled trials using them have been performed to prevent stone recurrence. Some lactic acid bacteria can degrade oxalate in vitro. This study sought to reduce urinary oxalate excretion in calcium stone formers with idiopathic hyperoxaluria. DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS A randomized, double-blind, placebo-controlled trial was performed of Oxadrop, a mix of four lactic acid bacterium species. This preparation previously reduced oxalate excretion in stone formers with idiopathic and enteric hyperoxaluria. Patients were selected from two stone prevention clinics. Twenty people with calcium stones and idiopathic hyperoxaluria (>40 mg/d) were enrolled and randomly assigned 1:1 in placebo and active preparation arms. Both groups took 3.6 g of granulate each day: Either placebo or the experimental preparation. Participants performed two consecutive 24-h urine collections at baseline, at 28 d of therapy, and at 56 d, after being off the preparation for 4 wk. Diet was replicated at each point. RESULTS There was no effect of the study preparation: Mean 24-h urinary oxalate excretion in placebo-treated patients was 73.9 mg at baseline and 72.7 mg after treatment, whereas the Oxadrop-treated patients had 59.1 mg at baseline and 55.4 mg after treatment. The preparation was well tolerated; three participants on active treatment experienced mild constipation. CONCLUSIONS In this randomized, placebo-controlled trial, Oxadrop did not reduce urinary oxalate excretion in participants with idiopathic hyperoxaluria.