Background: Bile acid metabolism in preterm infants is yet to be fully characterized. We compared the developmental pattern of urinary bile acid profiles in ten infants born at gestational ages from 25 to 33 weeks with previous data from full-term infants from birth to about 7 months of age.
Methods: Gas chromatography-mass spectrometry was performed on serial samples.
Results: Total urinary bile acid concentrations gradually increased until 1 to 2 months of age. After this peak of excretion (30 to 60 micromol/mmol creatinine), total urinary bile acid concentrations gradually decreased to less than 20 micromol/mmol creatinine. The percentage of usual bile acids (mainly cholic acid) relative to total urinary total bile acids gradually deceased from approximately 30% at birth to less than 15% at 7 months of age. On the other hand, 1beta-hydroxylated bile acids (mainly 1beta,3alpha,7alpha,12alpha-tetrahydroxy-5beta-cholan-24-oic acid) relative to total urinary bile acids were increased gradually from 60% at birth to reach 70% to 80% at 1 month of age. The percentage of 1beta-hydroxylated bile acids relative to total urinary bile acids then remained stable at a high percentage (70% to 90%) until the age of 7 months.
Conclusion: Physiological cholestasis in preterm infants persists longer than in full-term infants. Moreover, as large amounts of cholic and 1beta,3alpha,7alpha,12alpha-tetrahydroxy-5beta-cholan-24-oic acids were detected in urine from preterm infants during this study, the 25-hydroxylation pathway may be particularly important for bile acid synthesis in early preterm infants.