Sequential Serum Aluminum and Urine Aluminum: Creatinine Ratio and Tissue Aluminum Loading in Infants With Fractures/Rickets

Aluminum toxicity is associated with the development of bone disorders, including fractures, osteopenia, and osteomalacia. Fifty-one infants with a mean (± SEM) birth weight of 1007 ± 34 g, gestational age of 28.5 ± 0.3 weeks, and serial radiographic documentation at 3, 6, 9, and 12 months for the presence (n = 16) or absence (n = 35) of fractures and/or rickets were studied at the same intervals to determine the serial changes in serum aluminum concentrations and urine aluminum-creatinine ratios. Autopsy bone samples were used to determine the presence of tissue aluminum. Serum aluminum concentrations from 46 infants were stable and similar between groups, with mean values between 15 and 22 µg/L. Urine aluminum-creatinine (micrograms per milligram) ratios from 14 infants were higher in infants with fractures and/or rickets (0.26 ± 0.06 vs 0.12 ± 0.04) at onset, and rate of decrease in aluminum-cratinine ratio was faster in infants without fractures and/or rickets. All but three infants were tolerating complete enteral feeding at all sampling points. One infant who received aluminum-containing antacid had marked increase in serum aluminum to 83 µg/L while urine aluminum-creatinine ratio increased from 0.09 to a peak of 8.53. Vertebrae from three infants at autopsy (full enteral feeding was tolerated for 37 and 41 days in two infants, respectively) showed aluminum deposition in the zone of provisional calcification and along the newly formed trabecula. It is concluded that in enterally fed very low birth weight infants, serum aluminum levels and urine aluminum-creatinine ratios were similar in infants with and without fractures and/or rickets, presumably in part from modulation of aluminum absorption. However, aluminum absorption can be increased as indicated by increased serum and urine aluminum concentrations from aluminum antacid therapy. Bone accumulation of aluminum is possible with currently used enteral and parenteral nutrients, but the critical level of tissue aluminum loading associated with development of fractures and/or rickets remains to be determined.