AUA 2018: Citrate Excretion in the Metabolic Stone Clinic Setting

San Francisco, CA USA ( Dr. Natasza Posielski, a Urology resident from the University of Wisconsin, Madison presented her data on the effects of magnesium supplementation on urinary citrate excretion. Although urinary magnesium excretion has been associated with urinary citrate excretion, there are few studies that have analyzed the potential therapeutic effects of magnesium supplements for patients with hypocitraturia. Dr. Posielski and her team of researchers wanted to determine if magnesium (Mg) supplementation could increase urinary citrate excretion levels in hypocitraturic patients who are at risk for calcium oxalate stone formation.

The study included 117 patients with low urinary magnesium (UMg) below 70 mg/day in their first 24-hour urine collection seen at their multidisciplinary stone clinic between 2009-2016. Patients without 24-hour urine collections, patients who had >40% difference in urinary creatinine excretion, or patients with >2 years between 24-hour urine collection were not included in this study. The primary outcomes analyzed for this study were UMg and urinary citrate (UCit) excretion in 24-hour urine collections. 34% of 117 patients were recommended over-the-counter Mg supplementation (300-500 mg/day) and 66% of the cohort were not recommended the supplements, although patients were advised to increase their magnesium intake through their diet. Approximately 70-80% of patients in both groups were known calcium oxalate stone formers, and 45% were hypocitraturic.

The results of this study found that patients in both groups experienced a significant increase in Mg levels, however a significant increase in UCit was only found in the group of patients taking the Mg supplements. Of note, patients with UMg below 40 mg/day had minimal response to the oral Mg supplementation.

Dr. Posielski and her team concluded that in patients with hypocitraturia and low Mg excretion levels, oral Mg supplementation could be beneficial in correcting hypocitraturia. After her presentation, Dr. Posielski was asked if there were concerns about the gastrointestinal side effects of Mg supplementation >350 mg/day. Dr. Posielski reported that while some of her patients experienced occasional discomfort, there were no significant side effects reported. Further studies are needed to determine the efficacy of magnesium supplements as a therapeutic treatment for patients with hypocitraturia.

Presented by Natasza Posielski, MD

Written by: Taylor Capretz, Department of Urology, University of California-Irvine at the 2018 AUA Annual Meeting - May 18 - 21, 2018 – San Francisco, CA USA
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