Assessment of Serum Level of Vitamin D in Infants with Nephrolithiasis

Introduction. Detection of nephrolithiasis is readily possible in infants with the advent of new imaging technology. Vitamin D is routinely given to newborn infants shortly after birth during infancy. Vitamin D is known to increase urinary calcium excretion which may be responsible for the increased incidence of nephrolithiasis during infancy. To test this hypothesis we studied the serum level of vitamin D and renal handling of calcium in infants with nephrolithiasis. Methods. In this prospective case-controlled study, we measured serum levels of vitamin D and calcium accompanied by urinary calcium level in infants between 1 to 12 months with nephrolithiasis who fed with breast milk and vitamin D supplement and compared these parameters with healthy infants without nephrolithiasis after matching for sex and postnatal age as the control group. All infants with nephrolithiasis were evaluated for metabolic disorders and other risk factors and positive cases were excluded from the study. Results. Fifty infants between 1 to 12 months with mean postnatal age 6.96 +/- 2.29 months with nephrolithiasis and 50 control infants with mean postnatal age 6.94 +/- 2.55 months were enrolled in the study. Mean serum level of vitamin D in the case and control groups was 41.49 +/- 11.69 and 35.67 +/- 6.76 ng/ mL, respectively. Mean serum level of calcium in case group was 9.63 +/- 0.32 vs. 8.59 +/- 1.21 mg/ dL in the control group. Mean urinary calcium- creatinine ratio (Ca/Cr) in the study and control groups was 0.15 +/- 0.16 and 0.08 +/- 0.02, respectively, Differences were statistically significant in all three variables (P < .05). Conclusion. Routine consumption of vitamin D increases urinary level of calcium and in presence of other predisposing factors could accelerate the genesis of nephrolithiasis in infants.