To the great surprise of parents, kidney stones, once considered
a disorder of middle age, are now showing up in children as young as
5 or 6.
While there are no reliable data on the number of cases,
pediatric urologists and nephrologists in the United States say
they are seeing a steep rise in young patients. Some hospitals have
opened pediatric kidney stone clinics.
"The older doctors would say in the '70s and '80s, they'd see a
kid with a stone once every few months," said Dr. Caleb Nelson, a
urology instructor at Harvard Medical School who is co-director of
the new kidney stone center at Children's Hospital Boston. "Now we
see kids once a week or less."
Dr. John Pope IV, an associate professor of urologic surgery and
pediatrics at the Monroe Carell Jr. Children's Hospital at
Vanderbilt in Nashville, Tennessee, said, "When we tell parents,
most say they've never heard of a kid with a kidney stone and think
something is terribly wrong with their child."
In China recently, many children who drank milk tainted with
melamine - a toxic chemical illegally added to watered-down milk to
inflate the protein count - developed kidney stones.
The increase in the United States is attributed to a host of
factors, including a food additive that is both legal and
ubiquitous: salt.
Though most of the research on kidney stones comes from adult
studies, experts believe it can be applied to children. Those
studies have found that dietary factors are the leading cause of
kidney stones, which are crystallizations of several substances in
the urine. Stones form when these substances become too
concentrated.
Forty to 65 percent of kidney stones are formed when oxalate, a
byproduct of certain foods, binds to calcium in the urine. (Other
common types include calcium phosphate stones and uric acid stones.)
And the two biggest risk factors for this binding process are not
drinking enough fluids and eating too much salt; both increase the
amount of calcium and oxalate in the urine.
Excess salt has to be excreted through the kidneys, but salt
binds to calcium on its way out, creating a greater concentration of
calcium in the urine and the kidneys.
"What we've really seen is an increase in the salt load in
children's diet," said Dr. Bruce Slaughenhoupt, co-director of
pediatric urology and of the pediatric kidney stone clinic at the
University of Wisconsin. He and other experts mentioned not just
salty chips and french fries, but also processed foods like sandwich
meats, canned soups, packaged meals and even sports drinks like
Gatorade, which are so popular among schoolchildren they are now
sold in child-friendly juice boxes.
Children also tend not to drink enough water. "They don't want to
go to the bathroom at school; they don't have time, so they drink
less," said Dr. Alicia Neu, medical director of pediatric nephrology
and the pediatric stone clinic at Johns Hopkins Children's Center in
Baltimore. Instead, they are likely to drink only when thirsty, but
that may be too little, especially for children who play sports or
are just active. "Drinking more water is the most important step in
the prevention of kidney stones," Neu said.
The incidence of kidney stones in adults has also been rising,
especially in women, and experts say they see more adults in their
20s and 30s with stones; in the past, it was more common in adults
in their 40s and 50s.
"It's no longer a middle-aged disease," Nelson said. "Most of us
suspect what we're seeing in children is the spillover of the
overall increase in the whole population." The median age of
children with stones is about 10.
Many experts say the rise in obesity is contributing to kidney
stones in children as well as adults. But not all stone centers are
seeing overweight children, and having a healthy weight does not
preclude kidney stones. "Of the school-age and adolescent kids we've
seen, most of them appear to be reasonably fit, active kids," Nelson
said.
Slaughenhoupt has seen more overweight children at his clinic.
"We haven't compared our data yet," he said, "but my sense is that
children with stones are bigger, and some of them are morbidly
obese."
Pope, in Nashville, agreed. His hospital lies in the so-called
stone belt, a swath of Southern states with a higher incidence of
kidney stones, and he said doctors there saw two to three new
pediatric cases a week. "There's no question in my mind that it is
largely dietary and directly related to the childhood obesity
epidemic," he said.
Fifty to 60 percent of children with kidney stones have a family
history of them. "If you have a family history, it's important to
recognize your kids are at risk at some point in their life," Nelson
said. "That means instilling lifelong habits of good hydration,
balanced diet, and avoiding processed high-salt, high-fat foods."
There is also evidence that sucrose, found in sodas, can increase
the risk of stones, as can high-protein weight-loss diets, which are
growing in popularity among teenagers.
A common misconception is that people with kidney stones should
avoid calcium. In fact, dairy products have been shown to reduce the
risk of stones, because the dietary calcium binds with oxalate
before it is absorbed by the body, preventing it from getting into
the kidneys.
Children with kidney stones can experience severe pain in their
side or stomach when a stone is passing through the narrow ureter
through which urine travels from the kidneys to the bladder. Younger
children may have a vaguer pain or stomachache, making the condition
harder to diagnose. Children may feel sick to their stomach, and
often there is blood in the urine.
Last February, Tessa Cesario, 11, of Frederick, Maryland, began
having back pains. An aspiring ballerina, she was used to occasional
aches and strains. But this one was so intense that her parents took
her to the doctor, who ordered an X-ray. When he phoned with the
results, her parents were astonished. Her mother, Theresa Cesario,
said, "I thought older men get kidney stones, not kids."
The treatment for kidney stones is similar in children and
adults. Doctors try to let the stone pass, but if it is too large,
if it blocks the flow of urine or if there is a sign of infection,
it is removed through one of two types of minimally invasive
surgery.
Shock-wave lithotripsy is a noninvasive procedure that uses high-
energy sound waves to blast the stones into fragments that are then
more easily passed. In ureteroscopy, an endoscope is inserted
through the ureter to retrieve or obliterate the stone.
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