Clinical observation of childhood urinary stones induced by melamine-tainted infant formula in Anhui province, China

INTRODUCTION: The current report detailed an investigation of melamine-linked urinary stones in children exposed to contaminated formula. MATERIAL AND METHODS: A total of 1062 children fed with melamine-contaminated infant formula were screened for urinary stones. Sixty healthy children without melamine exposure were recruited as a control group. Ultrasonography of the urinary tract system was performed. Urinalysis, renal function, liver status, and serum electrolytes were determined. RESULTS: We encountered 49 affected children from the 1062 screened ones, at a rate of 4.6% per ultrasound performed. Thirty-two were male, and 17 were female. The affected children ranged in age from 1 month to 96 months, with a mean of 25 months. Duration of exposure was from 1.3 months to 84 months, with a mean of 19.5 months. The melamine contents in serum were between 12 mg/kg and 2563 mg/kg, with mean concentration of 1295.3 mg/kg. Most affected children were asymptomatic with no urinary findings. Patients with urinary stones exhibited lower urine pH and serum HCO(3) (–) than those in the healthy children, whereas for serum uric acid, alanine aminotransferase, aspartate aminotransferase, and anion gap the opposite trends were observed. The stone diameter ranged from 2 mm to 18 mm with a median of 6.5 mm. Multiple stones were noted in all patients. After 1 week of conservative management, stone diameters of 38 cases (77.6%) were significantly decreased. Among them, urinary stones were discharged completely in 21 affected children (42.9%). CONCLUSIONS: The short-term outcome of melamine-linked urinary stones is satisfactory.