To the Editor: The recent melamine contamination of infant formulaand milk products in China placed thousands of children in Chinaand neighboring regions at risk for renal-stone formation andrenal failure; six deaths were reported. In the wake of thecrisis, screening programs were launched nationwide in the mainlandof China. A similar program was initiated in Hong Kong1; here,we describe the results.
From September 28 through October 17, 2008, a total of 2140children (1177 boys and 963 girls; age range, 1 month to 12years; mean age, 6.45 years), all asymptomatic, underwent ultrasonographicscreening at Prince of Wales Hospital, one of the designatedspecial assessment centers in Hong Kong. On ultrasonography,a stone (nonobstructive, 7 mm in length) was detected in onlyone child. Another child had increased echogenicity in bothrenal papillae. Six additional children had small, discrete,hyperechoic renal foci (<4 mm in diameter) near the renalpapillae, all of which were associated with "comet-tail" artifacts2on gray-scale ultrasonography (Figure 1). A "twinkling artifact"3was revealed by color Doppler imaging in two of the six childrenwith hyperechoic foci. Limited low-dose computed tomographyof the kidneys was performed in two of the six children andconfirmed the presence of calcific foci.
Figure 1. Longitudinal Ultrasonogram of the Right Kidney in an 8-Year-Old Girl.
A small hyperechoic focus with a "comet-tail" artifact (arrowhead) is visible near a lower-pole hypoechoic pyramid (arrow) in an otherwise normal kidney. The child had ingested about 250 ml of the contaminated milk each day for a year.
It is unclear whether these echogenic renal foci were relatedto melamine-crystal deposition or were incidental findings.Renal histopathological characteristics in cats exposed to melaminehave been shown to be due to melamine crystals, primarily withinthe distal tubules.4 It is unknown whether filtered melaminecrystals are trapped within the distal tubules in humans, renderingthe renal papillae a susceptible site for deposition and aggregation.Currently, there is no noninvasive test that would ascertainthe nature of these echogenic foci.
We encouraged the families of the children we screened to ensureadequate hydration, and we have planned for follow-up ultrasonographyto be performed in the eight children with abnormal findings,3 months after the initial studies.
Our current report from Hong Kong indicates that the adverseeffects of melamine-tainted milk products do not initially appearto be as severe as first anticipated. In populations exposedto doses of melamine similar to those among the children inHong Kong,5 screening by means of ultrasonography is likelyto identify few findings and findings of unclear clinical relevance.
Stella Sin Yee Ho, Ph.D. Winnie Chiu Wing Chu, F.R.C.R. Ka Tak Wong, F.R.C.R. Chi Kong Li, M.D. William Wong, F.R.C.P. Pak Cheung Ng, M.D. Anil T. Ahuja, F.R.C.R. Chinese University of Hong Kong Hong Kong, China aniltahuja{at}cuhk.edu.hk
Supported by the government of the Hong Kong Special AdministrativeRegion. The authors are independent of the sponsor.
This letter (10.1056/NEJMc0809955) was published at NEJM.orgon February 4, 2009.
References
Updated guidelines for assessment and treatment of melamine tainted milk product related disorders. Operations circular no. 23/2008. Hong Kong: Hospital Authority Head Office, 2008.
Shapiro RS, Winsberg F. Comet-tail artifact from cholesterol crystals: observations in the postlithotripsy gallbladder and an in vitro model. Radiology 1990;177:153-156. [Free Full Text]
Rahmouni A, Bargoin R, Herment A, Bargoin N, Vasile N. Color Doppler twinkling artifact in hyperechoic regions. Radiology 1996;199:269-271. [Free Full Text]
Puschner B, Poppenga RH, Lowenstine LJ, Filigenzi MS, Pesavento PA. Assessment of melamine and cyanuric acid toxicity in cats. J Vet Diagn Invest 2007;19:616-624. [Free Full Text]
Unsatisfactory results of testing of melamine: test results of dairy products. Hong Kong Special Administrative Region: Centre for Food Safety, October 2008. (Accessed February 20, 2009, at http://www.cfs.gov.hk.)
Wang, I J, Wu, Y N, Wu, W C, Leonardi, G, Sung, Y J, Lin, T J, Wang, C L, Kuo, C F, Wu, K Y, Cheng, W C, Chan, C C, Chen, P C, Lin, S-L
(2009). The association of clinical findings and exposure profiles with melamine associated nephrolithiasis. Arch. Dis. Child.
94: 883-887
[Abstract][Full Text]
Langman, C. B.
(2009). Melamine, Powdered Milk, and Nephrolithiasis in Chinese Infants. NEJM
360: 1139-1141
[Full Text]
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