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Ambient temperature tied to kidney stone production

NEW YORK (Reuters Health) – In patients with nephrolithiasis, higher ambient temperatures are associated with increased excretion of agents linked to stone production, new research shows.

“Several previously published studies have shown that hotter weather is associated with increased rates of stone formation. In this study, we examined a group of stone formers who completed 24-hour urine studies for the purposes of prevention. We found that those who collected their urines on hotter days excreted more calcium,” Dr. Brian H. Eisner told Reuters Health in an email.

In a May 11 online paper in BJU International, Dr. Eisner of Boston’s Massachusetts General Hospital and colleagues report on 599 patients seen at four metabolic stone clinics.

The average ambient temperature overall during the study period was 16.9 C – but the mean ranged from 7.8 C at a clinic in New Hampshire to 32.9 C at one in Arizona.

On multivariate linear regression analysis, increasing temperature was associated with increasing urine calcium, super-saturation of calcium oxalate, and super-saturation of calcium phosphate as well as decreasing urine sodium – regardless of humidity and season.

There were no changes in urine volume, contrary to many reports that have suggested dehydration or reduced volume is the driving force behind kidney stone formation, the authors point out.

“These findings may be useful for stone prevention in hotter climates, and we hope that future studies will be able to examine the mechanism underlying these findings,” Dr. Eisner said.

But, he and his colleagues acknowledge, the study only included stone formers, “so the results may not be applicable to persons without a history of nephrolithiasis.”

SOURCE: http://bit.ly/L4Kyw7

BJU Int 2012.