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

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, beta 2-microglobulin (MG), cystatin C (Cys C), urinary Cr (UCr), microalbumin (mALB), alpha 1-MG, beta 2-MG, n-acetyl-beta-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 degrees and 27.7 degrees (2 theta). 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 beta 2-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). alpha 1-MG/UCr and beta 2-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.