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Contemporary 24-hour Urine Collection Analysis Reveals High Risk Stone Formers May Be at Increased Risk for Recurrence in Summer and Winter Months
Sammy E Elsamra, Michael Lasser, Simone Thavaseelan, George Haleblian, Gyan Pareek
Warren Alpert Medical School of Brown University, Providence, RI
Introduction:
Climate and geography have been shown to play a role in stone risk, with populations in warmer climates exhibiting a greater prevalence of nephrolithiasis. None of these studies are from the northeast and many reveal no decrease in urinary volume in the summer. We evaluated high-risk stone formers in our region to determine if a seasonal variation in urine volume exists.
Materials & Methods: 963 24-hour urine specimens from high risk stone formers (2005-2010) were stratified by season (Winter-Dec, Jan, Feb; Spring-Mar, Apr, May; Summer-Jun, Jul, Aug; Fall-Sep, Oct, Nov) and seasonal mean 24-hour urine volume was compared via Student T test.
Results:
Of 963 urine studies, 472 (49%) were male and 482 (51%) female. Mean (+ standard deviation) 24-hour urine volumes (liters) for spring, summer, fall, and winter were 1.9 + 0.97, 1.79 + 0.9, 2.02 + 0.87, and 1.84 + 0.76, respectively. Student's T-test was used to compare each season in a round-robin fashion. Significant differences were noted between summer and fall as well as winter and fall with both summer and winter associated with significantly lower volumes than fall (p=.007 and p=0.014, respectively).
Conclusions:
High-risk stone formers in the northeast produce lower urine volumes in the summer and winter. Frigid winters may increase exposure to arid indoor heating with similar effects on hydration. Urologists treating high-risk stone formers, in the northeast, should be aware of both of these two seasonal variations to facilitate proper hydration counseling to high-risk stone formers.
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