The US must brace itself for an increase in cases of kidney stones provoked by rising temperatures, scientists this week warned.

Said stones are caused by salts crystallising in the kidneys, something often provoked by dehydration, especially in warmer climes. Accordingly, southeastern US states - the so-called kidney stone "belt" - suffer 50 per cent more cases than northeastern ones. Nationwide, an average of 12 per cent of all men and seven per cent of women can expect to be afflicted over their lifetimes.

The scientists' report, delivered on Monday in the Proceedings of the National Academy of Sciences, warns that calculations based on figures produced by the United Nations-sponsored Intergovernmental Panel on Climate Change, which estimate a global temperature rise of 3 to 7°C this century, coupled to Medicare and Veterans Administration health records stretching from 1982 to 2005, predict the following effects:

• High-risk zones will cover 56 per cent of states by 2050 and 70 per cent by 2095
• Midwestern states "will take the brunt of the expansion if cases rise in straight-line fashion with temperature", as USA Today puts it
• The cost of treating kidney stones will rise 25 per cent by 2050, a bump of at least $900m compared with 2000

Report co-author Margaret Pearle, of the University of Texas Southwestern Medical School in Dallas, said: "We see a relationship between kidney stones and temperatures everywhere. Even in places with air conditioning, warmer temperatures mean more stones." ®

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