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Previous Volume 360:1157-1158 March 12, 2009 Number 11 Next

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To the Editor: The adverse renal effects of melamine-tainted formula have raised international concern. To address public concerns about melamine, the department of health in Taiwan initiated services to screen exposed children.

From September 24 through October 23, 2008, we screened 1129 children in Taiwan who had possible exposure to contaminated formula, investigating the clinical symptoms and risk factors for nephrolithiasis. Clinical presentation and urinary calcium and creatinine levels were evaluated, and urinalysis and renal ultrasonography were performed. We categorized our patients into three groups, according to exposure history.^1,2 The high-exposure group consisted of children who consumed dairy products from the mainland of China presumed to be highly contaminated (e.g., Sanlu or Mengniu brand, with melamine levels reported as exceeding 2.5 ppm).¹ The low-exposure group comprised children who consumed brands of contaminated milk with lower measured melamine levels (e.g., Klim or Neslac imported from the mainland of China, with melamine levels of 0.05 to 2.5 ppm).² The control group consisted of children who consumed brands of milk without detected melamine levels (<0.05 ppm).²

There were 44 children in the high-exposure group; none had hematuria, hypercalciuria, flank pain, or acute renal failure (Table 1). Nephrolithiasis and a history of residence in the mainland of China were significantly more frequent in the high-exposure group than in the other two groups (P<0.001). In the high-exposure group, children with nephrolithiasis were younger than those without nephrolithiasis (mean ±SD, 2.33±1.12 vs. 4.83±2.64 years; P=0.009). The mean duration of exposure was 7.19 months (range, 0.67 to 36) in the high-exposure group and 17.40 months (range, 3 to 48) in the low-exposure group.

View this table: [in this window] [in a new window]   Table 1. Baseline Characteristics of the Study Children, According to Melamine Exposure.

 
The most common metabolic risk factor for stone formation is hypercalciuria, which in the past has been described in 75 to 80% of children with nephrolithiasis.³ Hematuria as a presenting symptom for nephrolithiasis is also reported to vary, from 30 to 55%.⁴ However, neither hypercalciuria nor hematuria was detected in any of the nine children in the high-exposure group with nephrolithiasis associated with the consumption of dairy products from the mainland of China. Plain abdominal radiography in these patients was negative; the stones were detected on ultrasonography. The negative plain films suggest that stones related to melamine ingestion are relatively radiolucent and do not contain substantial amounts of calcium.

Consumption of melamine-contaminated dairy products appeared to be a major factor in the development of nephrolithiasis in the children we screened. Furthermore, the children in the high-exposure group in whom nephrolithiasis developed were all under the age of 3 years. Because of the lack of symptoms and signs, we recommend that ultrasonography be performed in children exposed to melamine-contaminated formula.

I-Jen Wang, M.D., Ph.D.
Taipei Hospital Department of Health
Taipei 242, Taiwan

Pau-Chung Chen, M.D., Ph.D.
National Taiwan University College of Public Health
Taipei 10055, Taiwan

Kung-Chang Hwang, M.D., M.P.H.
Hospital Administration Commission
Taipei 100, Taiwan
r92846001{at}ntu.edu.tw

Supported by grants from the National Science Council of Taiwan (NSC 97-2314-B-192-001-MY2).

This letter (10.1056/NEJMc0810070) was published at NEJM.org on February 4, 2009.

References

1. List of milk products that are confirmed to be positive for melamine. Geneva: International Food Safety Authorities Network, 2008. (Accessed February 20, 2009, at http://www.moh.gov.bn/download/list-of-confirmed-contaminated-products.pdf.) 
2. Results of investigation in dairy products with melamine. Taiwan: Bureau of Health, Taipei City Government, 2008. (Accessed February 20, 2009, at http://www.health.gov.tw/Default.aspx?tabid=546&mid=1287.)
3. Stapleton FB. Clinical approach to children with urolithiasis. Semin Nephrol 1996;16:389-397. [Web of Science][Medline]
4. Coward RJ, Peters CJ, Duffy PG, et al. Epidemiology of paediatric renal stone disease in the UK. Arch Dis Child 2003;88:962-965. [Free Full Text]

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