When pediatric urologist Barry Duel began practicing 11 years ago, it was rare to see a healthy child with kidney stones. These days, he sees two to three new children with stones a month.
Craig Langman, head of the department of kidney diseases at Children's Memorial Hospital in Chicago, has 800 pediatric patients in his files with kidney stones. More than half of them are from the past five years.
The increase prompted Duel to create a pediatric stone center in October at Cedars-Sinai Medical Center, where he works. Other new centers have been created as doctors across the country noted similar trends.
"We don't want to raise the alarm bells that we have an epidemic, but this is something we see and something to be aware of," Duel says.
Kidney stones are small, hard masses of mineral and acid salts that separate from the urine and solidify in the kidney. Most commonly, they are made of calcium oxalate or calcium phosphate, although other types exist.
Urine typically contains chemicals such as citrate, magnesium and pyrophosphate that prevent these crystals from forming. Stone patients can have low levels of these chemicals, causing stone formation. Stones can also form when a person is dehydrated, lacking the fluid to flush the minerals that form stones.
About 1 million Americans are treated each year for kidney stones, according to the National Kidney Foundation. They are most common in patients ages 20 to 40, and are more common in men than women.
Specialists know that kidney stones in children are caused by hereditary factors, obesity and dietary habits. Even as infants, children can get kidney stones, but the peak age at which they occur in kids is typically around 10, a statistic that hasn't changed.
Root causes
Most urologists believe that the rise in rates is linked to the increase in childhood obesity and poor diets.
* Obesity. High levels of glucose, triglycerides, cholesterol and insulin affect acidity of the urine. Studies at UT Southwestern Medical Center in Dallas have shown that people with metabolic syndrome -- characterized by obesity, high blood pressure, diabetes and high cholesterol -- are at an increased risk for kidney stones. High levels of insulin, in particular, correlate with higher urine acid levels, which can cause uric acid stones.
Langman says he has seen an increase in overweight patients with stones, especially in African American and Latino children. He says stones almost never occurred in these groups just a few years ago.
