Defining 24-hour urine parameters and kidney stone risk of student athletes.

Abstract

Dehydration is a risk factor for kidney stone formation. Studying populations that may experience dehydration without a known increased incidence of stone formation may help understand stone formation and prevention. High-caliber athletes represent such a population. We characterized the urinary environment of high-caliber athletes utilizing 24-hour urine collections with comparison to non-athlete controls. After Institutional Review Board (IRB) and National Collegiate Athletic Association (NCAA) compliance officer approval, 74 college-student athletes and 20 non-athletes were enrolled. Demographics, medical history, and sport of participation were recorded. Participants were asked to provide 24-hour urine collections as well as diet and activity logs at the time of urine collection. Standard stone risk parameters were assessed and compared to litholink reference standards. 34 athletes and 10 non-athletes provided at least one 24-hour urine specimen for evaluation. Athletes had a high prevalence of urinary risks for stone formation including low volume (median 1.46L), low citrate, high sodium, high calcium (females), and high uric acid (males). However, athletes also had a high prevalence of known stone-protective factors such as high urine magnesium. Athletes had a lower urine pH but high supersaturation of uric acid and calcium oxalate compared to non-athletes. Student athletes appear to have a high prevalence of urinary risk factors for stone formation such as dehydration, high calcium, high uric acid, high sodium, and low citrate. Overall stone risk in this population may be offset by increased levels of stone-protective factors such as magnesium. Further study of this population may help generate hypotheses for effective stone prevention strategies in the general population.