Fetal Bile Acid Metabolism During Infancy: Analysis of 1β–Hydroxylated Bile Acids in Urine, Meconium and Feces

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Abstract
Fetal bile acids (1β–hydroxylated, 6α–hydroxylated and unsaturated bile acids), especially 1β,3α,7α, 12α–tetrahydroxy–5β–cholan–24–oic acid (CA–1β–ol), have been detected in urine and feces early in life. To investigate whether a fetal pathway of bile acid synthesis exists in infancy, we measured the concentrations of bile acids in the urine, meconium and feces from normal newborns and infants by means of gas chromatography—mass spectrometry. The mean ratio of total bile acids to creatinine in urine increased between birth and 7 days and then gradually decreased; however, the concentration of total bile acids in urine remained significantly higher than that in adult urine until 3 mo of age. The main urinary bile acid was CA–1β–ol, and substantial amounts of fetal bile acids were detected in urine until 3 mo of age. The ratio of cholic acid to chenodeoxycholic acid was abnormally low in meconium (mean, 0.44; range, 0.19 to 0.74), and hyocholic acid constituted 19.3% of total bile acids. The mean total bile acid content of feces decreased between birth and 7 days of age and thereafter increased. The mean percentage of fetal bile acids in feces decreased after birth, but substantial amounts were present in feces until 1 mo of age. Our data support the notion that a primitive pathway for the synthesis of fetal bile acids—such as CA–1β–ol, hyocholic acid and 3β–hydroxy–5–cholen–24–oic acid—may be responsible for excretion mechanisms of cholestatic bile acids during immaturity of hepatic excretory function in infants from birth until 3 mo of age. (Hepatology 1994;20:819-824).