Changes in urinary stone risk factors in hypocitraturic calcium oxalate stone formers treated with dietary sodium supplementation.

PURPOSE

We investigated the effects of supplemental dietary sodium on risk factors for urinary stone disease in stone forming patients with hypocitraturia.

MATERIALS AND METHODS

Ten patients diagnosed with recurrent isolated hypocitraturic calcium urolithiasis were identified. Baseline 24-hour urinalysis was performed with patients on their regular diet, including citrate replacement with 20 mEq potassium citrate 3 times per day. Strict daily dietary logs were kept for a 7-day period, during which patients had normal oral intake and potassium citrate replacement. Patients then received supplemental sodium chloride for 1 week (1 gm orally 3 times per day), in addition to their regular diets and potassium citrate supplementation. Dietary logs were continued and 24-hour urinalysis was performed at the end of 1 week of supplemental sodium. Risk factors for urinary stone disease were compared using the Student t test and ANOVA.

RESULTS

Two patients were unable to comply with sodium supplementation based on 24-hour urinalysis and, therefore, they were excluded from study. The remaining 8 patients were analyzed. Patients on supplemental dietary sodium demonstrated significantly increased mean urinary voided volume (933 ml per day above baseline, p <0.05) and mean urinary sodium excretion (66 mEq per day above baseline, p <0.05). There was no statistically significant change in urinary calcium, oxalate or uric acid. The urinary supersaturation relative risk ratio decreased for calcium oxalate stones (0.93 vs 0.63, p <0.05), while those of brushite, struvite and uric acid were not different before vs after supplemental sodium.

CONCLUSIONS

Dietary sodium supplementation resulted in an increased voided urine volume and decreased the relative risk supersaturation ratio for calcium oxalate stones in patients with a history of hypocitraturic calcium oxalate nephrolithiasis. Urinary calcium excretion as well as other urine parameters that are risk factors for nephrolithiasis was not changed. Sodium restriction may be inappropriate in patients with hypocitraturia and recurrent urinary stones. Sodium supplementation may be beneficial in these patients because it results in voluntary increased fluid intake.