AUA 2009 - Stone Disease: Evaluation & Medical Management - Does Rising Urine pH Increase the Stone Formation Rate? - Session Highlights

CHICAGO, IL, USA ( - Potassium citrate (KCit) therapy has been shown to have significant effects on urinary metabolic parameters and is a cornerstone of medical management for nephrolithiasis. As calcium phosphate stones are known to from in alkaline urine, it is controversial whether excess urinary alkalinization from KCit may increase risk of calcium phosphate calculi. Robinson et al. from Durham, NC, investigated whether patients receiving KCit, especially those with a urine pH > 6.5, were at increased risk for stone formation.

A retrospective cohort study was performed on patients who had 24-hour urinalyses before and after starting KCit therapy, a starting urine pH < 6.5 and known stone formation rates before and after therapy.

Of 1,480 Stone Center patients reviewed, 472 met inclusion criteria. There was no significant difference in the reduction of stone formation rates between those whose post-KCit urine pH was > 6.5 (6.92) versus those whose pH was < 6.5 (mean 6.04). Stone formation rate decreased by -1.62 for the pH > 6.5 group and -1.48 for the pH < 6.5 group. There was no significant correlation between stone formation rate and pH among all subjects.

The authors concluded that as there was an equally significant reduction in stone formation rates between those with post-KCit urine pH > 6.5 and < 6.5, the medication did not likely increase the risk of calcium phosphate stones. They suggested further investigation to identify if there are other risk factors which could promote calcium phosphate stone formation in patients on KCit with highly alkaline urine. The limitation of this study is that stone analyses were not presented so one can conclude that there was no difference in reduction of stone formation rates in general, but not necessarily for calcium phosphate stones.

Presented by Marnie R. Robinson, MD, et al. at the Annual Meeting of the American Urological Association (AUA) - April 25 - 30, 2009 - McCormick Place Convention Center - Chicago, Illinois, USA.

Written by Jennifer L. Young, MD, a Contributing Editor with UroToday.

The opinions expressed in this article are those of the Contributing Medical Editor and do not necessarily reflect the viewpoints of the American Urological Association. Full AUA Conference Coverage