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, paediatric urologists and nephrologists across the country say they are seeing a steep rise in young patients. Some hospitals have opened paediatric 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 P Nelson, a urology instructor at Harvard Medical School. “Now we see kids once a week or less.” 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 crystallisations of several substances in the urine. Stones form when these substances become too concentrated. 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.
