Dietary management of idiopathic hyperoxaluria and the influence of patient characteristics and compliance.

OBJECTIVE: To assess the efficacy of dietary management for the treatment of idiopathic hyperoxaluria in a large tertiary care center and examine the influence of patient factors, compliance, and follow-up on oxalate reduction, which has not been previously investigated.
METHODS: Retrospectively, 149 patients with kidney stones with idiopathic hyperoxaluria who received dietary management at our stone clinic were evaluated. Changes in urinary parameters on 24-hour urine collections were calculated for all patients and those with abnormal values in the overall short-term (30-240 days) and long-term (>240 days) time periods. Changes in urinary oxalate were evaluated with respect to patient characteristics and compliance measures.
RESULTS: Urine oxalate and supersaturation of calcium oxalate were significantly (P < .001) reduced by 8.9 ± 19.2 mg/d and 1.7 ± 4.3, respectively. A total of 48.3% of the patients reduced their urinary oxalate to normal. Urine oxalate reductions were similar in the short-term and long-term periods. Women lowered urine oxalate nearly twice as much as men (12.7 ± 2.0 mg/d vs 6.7 ± 2.2 mg/d, P = .022) and body mass index (BMI) negatively correlated with oxalate reduction (Pearson's r = -0.213). Reported noncompliance and keeping follow-up appointments did not affect oxalate, however, there was a significant correlation between increasing urine volume and reducing oxalate (Pearson's r = -0.21).
CONCLUSION: This study confirms that meaningful reductions of urine oxalate and supersaturation of calcium oxalate can be achieved with dietary management of hyperoxaluria on a larger clinical scale. Furthermore, we identified that women and patients with low BMIs had greater urine oxalate reductions and urine volume may also be used by clinicians as a measure of dietary compliance.