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

Purpose: Dehydration is a risk factor for kidney stone formation. Studying populations that may experience dehydra-tion 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. Materials and methods: After In-stitutional Review Board (IRB) and National Collegiate Athletic Association (NCAA) com-pliance 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 collec-tions 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. Results: 34 athletes and 10 non-athletes provided at least one 24-hour urine specimen for evalu-ation. Athletes had a high prevalence of uri-nary risks for stone formation including low volume (median 1.46 L), low citrate, high so-dium, 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. Ath-letes had a lower urine pH but high supersat-uration of uric acid and calcium oxalate com-pared to non-athletes. Conclusion: 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 in-creased 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.