Kidney stones afflict kids
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.
* Too much dietary sodium. Most stones are made of calcium, and an abundance of sodium causes the body to release more calcium into the urine. Physicians worry that sodium intake in children is on the rise because they are drinking more sodas, eating more often at restaurants and noshing on more convenience foods.
In a 2007 letter published in the journal Hypertension, pediatric nephrologists at the VU University Medical Center in Amsterdam used a database of urine samples to find if there was an increase in sodium intake by children in recent years. They found that pediatric patients ages 5 to 10 were getting more than 50% more sodium in 2005 compared with 1995.
A report published in 2001 by the U.S. Department of Agriculture’s Center for Nutrition Policy and Promotion found that 68% of children ages 7 to 9 were exceeding the maximum recommended sodium intake. This was probably because of an increase in consumption of salty snacks and fast food, the authors said.
* Lack of dietary calcium. This may seem counterintuitive because stones are made of calcium, but if children have a low calcium intake, it can cause their gastrointestinal tract to overabsorb the chemical oxalate, a component of stones.
Symptoms
Most adolescents with kidney stones experience persistent or recurrent stomach pain. This is sometimes accompanied by nausea, vomiting or back pain. The symptoms may come and go as the stone moves around.
In younger children, symptoms can mimic those of urinary tract infections, and sometimes there is blood in the urine. If there is an infection, children may have a fever.
Patients are typically diagnosed after a pediatrician takes a urine sample. But although stones are easily diagnosed, patients can sometimes be passed around between physicians before the problem is found because it is not on doctors’ radar, Duel says.
About 30% of adults who have stones have a cause that can be treated to prevent them from recurring. In children, as many as 90% have a treatable cause, Langman says.
Most stones smaller than 6 millimeters will pass on their own and parents should make sure children are offered pain medication and drink lots of fluids while waiting. But surgery may be needed if the stones are too large, the pain is too intense, there are signs of infection or a child is vomiting excessively.
The predominant types of surgery are noninvasive, Duel says. They include breaking up the stones with external shock waves or passing a wire through the kidney and using a scope to locate the stones to be broken into smaller pieces.
Once the stones pass and children are treated, they may recur. In a 2006 study in the journal Pediatric Clinics of North America, researchers at the University of Rochester Medical Center found that stones recurred in 67% of children after about four years. And a 2007 study by the North Shore-Long Island Jewish Medical Center found that stones returned in about 39% of the patients.
Several measures can help decrease the likelihood of a stone recurring again. Drinking lots of fluids (mainly water) keeps chemicals such as calcium oxalate from reaching high concentrations in the urine. Drinking lemonade, which contains citrate, helps prevent calcium from crystallizing in the urine. Physicians also recommend reducing salt intake and ensuring children are getting their recommended calcium, which is 800 milligrams for children ages 4 to 8 and 1,300 milligrams for ages 9 to 18.
Medical treatments include the use of diuretics; Langman says he has had success prescribing Thiazide, a diuretic that blocks the kidney’s excretion of calcium.
More information on kidney stones can be found on the National Kidney Foundation’s website at www.kidney.org.
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