One-year follow up of melamine-associated renal stones in Sichuan and Hong Kong

Abstract

Background: An outbreak of melamine-associated renal stones occurred in mainland China in 2008, which led to large scale community screening of renal stones in Hong Kong. We hypothesised Hong Kong children screened positive did not suffer from melamine-associated renal stones. Methods: This one-year follow-up study compared the clinical features, renal ultrasound findings, and urinary interleukin 8 (IL-8) and monocyte chemoattractant protein 1 (MCP-1) to urinary creatinine ratios between 44 Sichuan children admitted to hospital for melamine-associated renal stones and 22 Hong Kong children screened positive with renal stones. Results: The mean age (±SD) in months of the Sichuan children (25.7±23.8) was significantly lower than that of Hong Kong children (75.0±42.1, p<0.0001). The melamine concentration in the milk consumed by the Sichuan children was significantly higher than that by Hong Kong children. All 44 Sichuan children and only 15 of the 22 Hong Kong children consumed melaminetainted milk product (MTMP). All except one of the 15 Hong Kong children had their daily melamineintake below the WHO tolerable daily intake of 0.2 mg melamine/Kg body weight. At diagnosis, the median number of stones and the mean largest stone size in the Sichuan children (4, 6.3 mm) were significantly higher than that in Hong Kong children (1, 3.8 mm, p<0.01). By 12 months follow-up, 28% and 48% of the Sichuan and Hong Kong children still had renal stones respectively. Urinary IL-8/creatinine ratio was significantly higher in Sichuan children with stones than other groups at 6 and 9 months followup. By 12 months follow-up, no such difference was observed among any groups. The above findings did not differ significantly whether the comparison with the Sichuan children was with the whole cohort of 22 Hong Kong children or the 15 who had consumed MTMP. In contrast, the 2 groups of Hong Kong children with and without MTMP consumption were similar in their demographics and clinical features. Conclusions: Hong Kong children had significantly different clinical features including MTMP consumption as compared to Sichuan children, suggesting Hong Kong children did not suffer from melamine-associated renal stones.