Some environmental exposures can also lead to kidney stones in children. Recently, milk products in China that were tainted with the industrial chemical melamine were linked to an increase in the development of kidney stones in babies and children there.
"The problem is the melamine, which was directly toxic to the kidneys and was crystallizing out in the urine to form stones," Nelson said.
"As far as we know, this is an isolated problem and is not an issue here," Milliner said.
Fortunately, Milliner noted, two-thirds to three-quarters of the time physicians can pinpoint the cause or predisposing factors that can minimize or reduce the odds of recurrence in children and teens.
There are some cases, though, where the cause of kidney stones remains a mystery. Just ask Kate Mercier, who was first diagnosed with them at age 8 and has been through at least 12 operations related to her stones.
The 17-year-old high school senior in a suburb south of Boston still might not know exactly why she's so prone to forming kidney stones, but all the X-rays, CT scans and ultrasounds she's been through in her young life have helped her choose a career path. She's off to college next year to study radiology, where she might have an edge on her classmates because of her firsthand familiarity with the procedures -- and plenty of compassion for the patients.
Although Mercier's been through a lot of surgeries for her kidney stones, she said, "I've never had pain. I have twinges from time to time, but they almost feel like muscle contractions."
In her case, there is a family history: Both her father and her aunt have had kidney stones. But each of them had only one stone, whereas Mercier tends to form clusters of them. And while she said, "I'll probably have them my whole life," she hasn't let them stop her from doing things -- including earning a brown belt in karate.
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