For children, a painful trend

Doctors seeing more young patients with kidney stones

fast-food diet may play part

December 29, 2006|By Jonathan Bor | Jonathan Bor,Sun reporter

Doctors at Johns Hopkins and other medical institutions are beginning to report a curious increase in children with kidney stones - another possible consequence of America's dependence on processed foods.

Bad eating habits have already fueled twin epidemics of childhood obesity and Type 2 diabetes. Although doctors have blamed fats and sugar for those ills, they say the culprit in this case may be two other features of the fast-food culture: too much salt and not enough water.

Though kidney stones remain uncommon among children, specialists who once treated only a few cases a year are trying to figure out why they are now seeing many times that number.

"Five years ago, we used to see maybe a handful of children a year, maybe five or six," said Dr. Yegappan Lakshmanan, a pediatric urologist at the Johns Hopkins Children's Center. "Now, it's five or six a month. Some are repeat patients, but it's definitely a trend."

Kidney stones, once found almost exclusively in adults, are tiny mineral deposits that can cause excruciating pain when they lodge in the urinary tract.

Three years ago, Hopkins established a pediatric kidney stone clinic after noticing an increase in cases. More recently, the Vanderbilt Children's Hospital in Nashville, Tenn., opened a stone clinic, and the Harvard-affiliated Children's Hospital in Boston is doing the same.

"We feel like we're seeing the same trend," said Dr. Caleb Nelson, a pediatric urologist at Harvard. "Whereas five or 10 years ago, you could go several months between [cases], now we see a couple a week."

Improved methods of diagnosing stones could be one reason for the sudden uptick of cases. They might account for larger numbers of children with stones too small to cause symptoms, doctors say, but not what many believe is an increase in children who arrive doubled over in pain.

"In children, we think diet has an important part to play - a lot of fast food with high salt content," Lakshmanan said.

Eating too much salt causes people to excrete excessive amounts of calcium, which can crystallize in the urine in the form of stones. That problem, Lakshmanan said, is compounded by the tendency of children to skimp on water, which in sufficient quantities can dilute the minerals that cause stones to form.

"We tell people to drink a lot of fluids, to empty their bladders frequently and not to take in a lot of salt," said Dr. Alicia Neu, a kidney specialist who, along with Lakshmanan, directs the Hopkins clinic.

The two are worried about schools that limit the number of times a child can visit the bathroom. Though teachers might be trying to curb abuse of bathroom privileges, they could inadvertently be playing a role in a growing medical problem. Holding one's urine can cause stones to form, he said.

Quantifying the problem is next to impossible because childhood kidney stones have never been carefully tracked. They remain far less common than in adults, who have a one in 10 lifetime chance of developing them. Those who have suffered one bout have a 50 percent chance of experiencing another in the next five years, Neu said.

Pediatricians have long known that certain congenital problems - including blockages in the kidney or bladder - can cause stones to form. Additionally, babies treated in intensive care units sometimes get medications that can predispose them to stones.

Those factors produced a small caseload, but nothing like the numbers doctors have seen more recently. Some asymptomatic children are diagnosed after doctors find minute calcium crystals in urine tests. Scans then confirm the presence of stones. But others appear first in the Hopkins emergency room with pain that's unforgettably intense.

"They didn't come to us just because we were stone specialists," Lakshmanan said.

Nelson agrees that it's too soon to declare diet the chief culprit, but he believes it's a leading candidate. At Harvard and Hopkins, dieticians are not only advising families about healthful eating habits, but also compiling dietary histories that could help solve the riddle.

"It does make sense that the fatter the country, the more stones you'll see," Nelson said. That doesn't necessarily mean that processed foods are causing kidney stones, he said. Children with kidney stones are more likely to be overweight than youngsters in years past - but youngsters in general are heavier than they used to be.

Nonetheless, there's general agreement that too much salt and too little water can lead to kidney stones. Similarly, panels convened recently by the American Medical Association and the National Academies of Science raised alarms about the salt content of the American diet.

"Keeping track of things like intake of salt and water is extremely difficult," Nelson said. "You go to grocery stores, and the intake of high-salt processed foods is through the roof."

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