The kidney stone and increased water intake trial in steel workers: results from a pilot study.

Preventing dehydration in subjects at risk may provide a means of primary prevention of kidney stones. The purpose of this pilot study was to assess the hydration status of an at-risk group of steel plant workers based on end-of-shift ('post-shift') spot urine osmolality and 24-h urinary stone risk parameters. 100 volunteers were recruited from Gerdau Midlothian steel mill in Texas on 11/14/14 and 12/5/14. Clinical data were recorded and post-shift spot urine sample was used to measure urine osmolality. Participants were invited to submit a 24-h urine sample within 4 weeks of enrollment. The mean age was 41 years and 95 % were men. The majority of subjects were white (75 %), followed by 10 % Hispanic and 9 % black. The mean body mass index was 30.1 kg/m2 and overall 16 % had a past history of stone disease. Mean post-shift urine spot osmolality was 704.5 mOsm (169-1165 mOsm) and was >800 and >700 mOsm in 39 and 57 %, respectively. Among 59 24-h urines samples, the mean volume was 1.89 ± 0.92 l/day, with 56 % < 2 L and 17 % < 1 L. Elevated levels of urinary analytes were found in 29 % of subjects for calcium (>250 mg/TV), 39 % for uric acid (>700 mg/TV), 25 % for oxalate (>45 mg/TV) and 50 % for sodium (>200 meq/TV). The prevalence of stone disease in this population of steel workers was higher than the published prevalence of stone disease in the general population. A significant number of workers had concentrated post-shift and 24-h urines and elevated levels of urinary analytes.

Increasing water intake by 2 liters reduces crystallization risk indexes in healthy subjects.

OBJECTIVE: The objective of the present study was to evaluate the effects of drinking 2 additional litres of water/day on several urinary risk factors for lithiasis in healthy subjects, through measurement of crystallization risk indices (Tiselius CRI). MATERIALS AND METHODS: 48 healthy subjects, aged 25 to 50 were studied for urinary parameters including CRI in the laboratory ward, for 24 hours. After this first period, they were randomized either to a 2L/d additional water intake (treated group) or usual fluid consumption (control group) for a 6 days period, which ended by a second measurement period in the laboratory ward for 24 hours. RESULTS: Total additional water intake was actually 1.3L/d on average in treated subjects, because subjects decreased other usual sources of fluid intake. In 24 hour urine, Tiselius CRI varied differently among treated subjects and controls between the 2 periods; male controls subjects experienced much higher values (above 2 in average in first morning urine sample) in the second period (p = 0.05). Of interest, in a transversal analysis, we observed a positive relation between BMI or waist circumference on the one hand, and with 24 hour urea excretion or osmotic load on the other hand. CONCLUSION: These results show a beneficial effect of a final 1.3L additional water intake on Tiselius CRI in healthy subjects.