Chicago ? Doctors are puzzling over what seems to be an increase in the number of children with kidney stones, a condition some blame on kids’ love of cheeseburgers, fries and other salty foods.

Kidney stones are usually an adult malady, notorious for causing excruciating pain — pain worse than childbirth. While the number of affected children isn’t huge, kids with kidney stones have been turning up in rising numbers at hospitals around the country.

At Children’s Hospital of Philadelphia, the number of children treated for kidney stones since 2005 has climbed from about 10 a year to five patients a week now, said Dr. Pasquale Casale.

Johns Hopkins Children Center in Baltimore used to treat one or two youngsters a year 15 or so years ago. Now it gets calls about new cases every week, said kidney specialist Dr. Alicia Neu.

Kids’ stones have been the talk of pediatric kidney specialists’ conferences, said Dr. Uri Alon, director of the bone and mineral disorders clinic at Children’s Mercy Hospital in Kansas City. Alon is involved in research trying to determine whether the increase is real and not just the result of greater awareness and better ways of detecting stones.

Alon also is studying whether improved nutrition can prevent kids’ kidney stones.