Plasma Conjugated Cholic Acid in Premature and Term Newborns and Young Infants

Bile acid handling by neonates, both premature (Group I, mean gestational age 34.3 weeks; Group II, 36.6 weeks) and full-term (Group III, 40.2 weeks) and by 3-month-old infants (Group IV) was assessed by measuring plasma concentrations of conjugated cholic acid (CCA) before and at successive intervals after feeds. The prefeeding CCA concentrations were highest in Group I (log mean 8.2; range 1.8--28.6 mumol/l) and lower in Groups II (7.5; 2.6--22.4 mumol/l), III (5.1; 2.1--11.1 mumol/L), and IV (2.2; 0.5--6.1 mumol/l). The mean postprandial increments correlated with maturity: the rises for Groups I--IV were 3.7, 4.3, 1.0 and 0.7 mumol/l, respectively. Peak values were consistently reached at 30 min after the start of the feed, i.e. strikingly earlier than in older children and adults. After the peaks the return to prefeeding levels occurred rapidly in Groups II--Iv but more slowly in the most premature infants (Group I). The rapid postprandial rise may be due to many factors, e.g., passive jejunal absorption, immature hepatic clearing mechanisms, or rapid transit of bile acids to the ileum. Hence, measurements of postprandial plasma bile acids would appear ill-suited for detection of disturbed ileal function in young infants. The high concentrations in healthy newborns suggest that caution is necessary in interpreting plasma bile acid concentrations during the first few weeks of life, especially in premature infants.