One more unwanted consequence of global warming may be an increase in cases of kidney stones in areas with rising temperatures, US researchers said.

Kidney stones - excruciatingly painful hard deposits of minerals and salts that can form in the kidneys - tend to be more common in hot climates, with dehydration a key risk factor for the condition.

The researchers used two mathematical models linking temperature to kidney-stone risk in the US, and found that regions where the condition is now most common will expand in coming decades due to predicted rising temperatures.

They forecast increases of up to 30 per cent in kidney stone cases in some areas - meaning millions more people would get the condition. The annual cost in the US of treating kidney stone cases could increase by 2050 by about $1 billion per year - 25 per cent more than current levels, they added.

Kidney stones currently are most common in the southeastern US, but this "kidney stone belt" is forecast to grow to the northward and westward, the researchers wrote in the journal Proceedings of the National Academy of Sciences. Other parts of the globe could experience similar trends.

"There's every reason to anticipate that it would be happening worldwide," urologist Margaret Pearle of the University of Texas Southwestern Medical Centre in Dallas, one of the researchers, said in a telephone interview.

Not drinking enough water and other fluids or losing too much fluids through dehydration - more likely in hotter climates - can leave one's urine with higher concentrations of substances that can form kidney stones. This is just the latest negative health consequence to be predicted due to climate change. Others include an increase in the many diseases spread by mosquitoes and other insects. In the US, about 12 per cent of men and seven per cent of women experience kidney stone disease at some time.