International

Renal Anaemia in the news

Melamine exposure linked to urolithiasis in young children

• 04 February 2009
• Reuters Health

NEW YORK (Reuters Health) - A study of kidney risks in Chinese children related to the contamination of milk with melamine is being published February 4th as an Online First issue of The New England Journal of Medicine. It shows that exposure to melamine-contaminated powdered formula increased the risk of urinary stones by up to sevenfold, but the clinical relevance of these stones, which often produce no symptoms or laboratory abnormalities, is unclear.

A jump in urolithiasis rates among young children occurred in China last year and the government announced in September that the epidemic was most likely due to melamine contamination of powdered-milk formula. The addition of melamine to the formula, it is believed, was a covert attempt to increase the apparent protein content since melamine contains a high amount of nitrogen.

In their study, Dr. Jie Ding, from Peking University First Hospital, and colleagues describe the investigation that ultimately linked melamine exposure to urolithiasis in young children. The study involved a parental survey for 589 children, 36 months of age or younger, who were being screened for melamine exposure and symptoms of urinary tract stones. Standard urinary function tests as well as ultrasonography were also performed.

Overall, 421 children consumed melamine-tainted formula. Fifty children had confirmed stones, including 8 children without melamine exposure; 112 had suspected stones, and 427 had no stones.

Hematuria and leukocyturia were seen in 5.9% and 2.9%, respectively, of children with stones, which is comparable to the rates seen in children without stones. Moreover, serum levels of creatinine, urea nitrogen, and alanine aminotransferase were usually normal in the patients with stones. Only 4 of 41 patients with stones had urinary markers suggesting glomerular dysfunction.

Children exposed to formulas with high melamine content (>500 ppm) were 7.0 times more likely to have urinary stones than those given formulas not tainted with melamine. Preterm infants were 4.5-times more likely to have stones than their full-term peers.

In related correspondence, a group from the Chinese University of Hong Kong reports that of 2140 children who underwent ultrasound screening from September 28 to October 17, 2008, just one was found to have urolithiasis. Some other abnormalities were noted in a few children, but their clinical significance, if any, is unclear, they add.

According to a related editorial, the American Society of Pediatric Nephrology advises a conservative approach for treating asymptomatic infants, "since stones presumed to have been induced by melamine appear to be passed easily after hydration" and because long-term follow-up data are lacking.

Ultrasound testing of all potentially exposed Chinese children living in the US is unlikely to be cost effective, editorialist Dr. Craig B. Langman, from Northwestern University, Chicago, comments.

N Engl J Med 2009;360.