Excessive fluid intake as a novel cause of proteinuria.

As part of a community screening study to assess the long-term health outcomes among residents of Walkerton, Ontario, after contamination of its municipal water supply by Escherichia coli O157:H7 and Campylobacter in 2000, we identified 100 adults who had proteinuria and polyuria but no medical history or medication use to explain their condition. Fifty-six of the 100 participants underwent both initial and confirmatory urine concentration tests, which showed that their urine osmolality could reach normal levels. We then instructed them to reduce their fluid intake to less than 2 L/d for 1 week. The proteinuria and polyuria were largely reversed by this manoeuvre. We do not know at this time whether the proteinuria associated with excessive fluid intake in these otherwise healthy people will affect their kidney function in the long term.