Assessment of chronic renal injury from melamine-associated pediatric urolithiasis: an eighteen-month prospective cohort study.

BACKGROUND

The illegal use of melamine in powdered baby formula resulted in a widespread outbreak of melamine-associated pediatric urolithiasis and kidney damage in China in 2008. We conducted this study because more needs to be known about the long-term effects of melamine-associated urolithiasis and kidney damage.

OBJECTIVES

To determine the prognosis and long-term implications of chronic kidney damage in children with urolithiasis resulting from melamine consumption.

DESIGN

Prospective cohort study.

SETTING

Children's Hospital of Fudan University.

PATIENTS AND

METHODS

Children six years of age or older with a history of having consumed melamine-contaminated milk powder were voluntarily screened. We measured urinary microprotein profiles [microalbumin (ALBU), immunoglobulin G (IgG), and n-acetyl-ß-d-glucosidase (NAG)] and creatinine (CR) results at 6 and 18 months in children with melamine-associated urolithiasis. This study was conducted from September 17 to October 15, 2008.

MAIN OUTCOME MEASURES: Changes in urinary microprotein profiles.

RESULTS

Of 8335 children screened, 102 children (1.22%) were diagnosed with melamine-associated urolithiasis. Follow-up rates at 6 and 18 months were 91.4% (96/105) and 89.2% (91/102), respectively. Eighteen months later, 90.3% patients had spontaneously passed a stone. The incidence rates of proteinuria and microscopic hematuria at 6 months were significantly higher than at 18 months (P=.029 and P=.017, respectively). The proportion of patients with abnormal ALBU/CR, IgG/CR and NAG/CR at 6 months (27.6%, 17.1% and 21.1%, respectively) was significantly higher than at 18 months (6.4%, 5.1% and 12.8%, respectively). The high concentration of melamine consumed was the primary factor correlated with the high microprotein levels. Approximately 90% melamine-associated urolithiasis cases can be resolved within 18 months by non-surgical therapy.

CONCLUSION

The long-term presence of stones associated with a previous exposure to melanine can cause chronic kidney glomerular and tubular injuries. Passing these stones as soon as possible can reduce kidney injury and accelerate recovery.

LIMITATIONS: We could not control for possible selection bias due to more visits to our hospital or visits to our hospital after diagnosis at other hospitals, which might have increased the rate of diagnosis.