Urolithiasis in children
As the prevalence of stone disease has grown, so has the importance of understanding disease process, diagnosis, and management.
Urolithiasis occurrence is increasing in both adults and children in the United States, with nearly 1 in 11 adults having a stone at some time in their life.1 Unfortunately, stone occurrence in children also appears to have increased from 1% to 2% in the 1950s to 1970s to almost 10%, where previously the rate of stone incidence was only 18 per 100,000 in 1999 to 57 per 100,000 in 2008. Adolescent girls (aged 12 to 18 years) have a higher rate of occurrence than the other groups studied, although the overall sex distribution in all age ranges was about the same.
Hospital admission rates for urolithiasis increased to 1 in 685 admissions in the 2002 to 2007 time period.
With more children and adolescents developing kidney and ureteral stones, it is critical that the pediatric care community (pediatricians, nurse practitioners, primary care providers, and family medicine physicians) understands how to evaluate, treat, and prevent recurrence of stones in their patients. This article provides background on the risk factors for stone disease, its presentation in children, and the changes in diet that increase that risk, and offers practical tips on the evaluation, treatment, and prevention of stones.
Pediatric stone disease has different geographic and racial prevalence rates. Stones are very common in the Middle East, Pakistan, India, and Southeast Asia. Children in developing countries tend to have more bladder calculi than calculi elsewhere in the urinary tract. Bladder stone composition in these children consists predominantly of ammonium acid, uric acid, and urate, likely because of the relatively low availability of dietary phosphate in these countries.2
Children of African descent worldwide rarely have stones, whereas in the United States, Caucasian children are more likely to suffer from urolithiasis, especially if they are from the Southeast region. Stones are more likely to be found in the kidneys and ureters than in the bladder in American children.
Previously, most children who developed kidney stones also had anatomic abnormalities that increased their likelihood to develop stones, such as obstruction of the ureter or renal pelvis, exstrophy, or static drainage with horseshoe kidney or megaureter. Now, between 40% and 50% of children with urolithiasis have metabolic abnormalities identified, whereas only 30% of stones are associated with genitourinary abnormalities. Most likely, the children with anatomic abnormalities and urolithiasis have concomitant metabolic risk factors.
Much of the increased incidence in stone formation in children and adolescents is attributed to major dietary changes in the United States over the past few years. The Centers for Disease Control and Prevention (CDC) recently published that the prevalence of obesity in children aged 2 to 19 years is about 17%, affecting about 12.7 million children and adolescents. The prevalence is particularly high in Hispanics (21.9%) and non-Hispanic blacks (19.5%), while it is only 14.7% in non-Hispanic white children.3
Children, particularly adolescents, are not drinking as much water or milk as they did previously. Increased consumption of sugary drinks has added to the increased obesity rates in children. Increased sodium consumption through processed foods also has increased stone formation through increased urine calcium excretion.
The most common abnormalities found have been hypercalcuria and hypocitraturia. Other metabolic problems seen, but less frequently, in children are hyperoxaluria, cystinuria, and hyperuricosuria. The most common stones found in US children are calcium oxalate (40% to 65% of all stones), calcium phosphate (14% to 30%), magnesium ammonium phosphate (struvite, 10% to 20%), cystine (5% to 10%), and uric acid (only 1% to 4%). In children, increased uric acid in urine promotes calcium oxalate stone formation, whereas uric acid stones are more commonly seen in adults.