Outcome of children with melamine-induced urolithiasis: results of a two-year follow-up

Abstract

Objective. Our purpose is to describe the characteristics and the outcome of melamine-induced renal and urinary tract injury in young children who consumed melamine-contaminated infant formula. Methods. This is a descriptive longitudinal study over 2 years in 240 children with melamine-induced urolithiasis screened in our hospital from September 15 to October 31, 2008. Ultrasonography and serum creatinine (SCr), urea, β2-microglobulin (MG), cystatin C (Cys C), urinary Cr (UCr), microalbumin (mALB), α1-MG, β2-MG, n-acetyl-β-d-glucosaminidase (NAG) and retinol-binding protein (RBP) measurements were performed. Results. The children ranged in age from 1 to 82 months, and 145 were males. The largest calculus was 33 mm in diameter. X-ray diffraction pattern of the calculi displayed two diffraction peaks at 10.9° and 27.7° (2θ). Surgical management was performed in 14 patients. In 226 patients without surgical management, the calculi were passed in 59.63% patients within 1 month, in 85.40% within 6 and in 91.15% within 24 months. Increased SCr and urea levels were noted in three and six patients, respectively, at the time of diagnosis. The SCr, serum β2-MG, and Cys C levels at the time of diagnosis were higher than those at 3 and 6 months after diagnosis (P < 0.05, respectively). The levels of mALB/UCr, NAG/UCr, and RBP/UCr at the time of diagnosis were higher than those at 3, 6, 12, and 24 months after diagnosis (P < 0.05, respectively). α1-MG/UCr and β2-MG/UCr levels at the time of diagnosis were similar to those at 3 months after diagnosis, and significantly higher than those in the follow-up period (P < 0.05, respectively). Conclusion. Melamine might injure both the renal glomerulus and the tubule, and that the predominant lesion is urolithiasis. The compositions of melamine-induced urolithiasis are melamine and cyanuric acid crystals. The urolithiasis might persist for over 2 years and cause irreversible damage. Therefore, a long-term follow-up for all patients is required.

Keywords:

• Melamine
• Infant formula
• Urolithiasis
• Calculus
• Kidney
• Child

Acknowledgments

We thank the children and their parents for participating in this research project. We thank the staff of the urology and ultrasound departments for their patient care and organization. We thank Li Ping He and Xiao Min Tang from the Center of Analysis and Measurement of Zhejiang University for their assay expertise.

Declaration of interest

The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.

This study was supported by the grant of Zhejiang Health Bureau (20082X010 and 2008ZX007) and Zhejiang Province innovation team for early screening and intervention of birth defects (2010R50045).