550 THE EXTENT OF MICROBIAL DEGRADATION OF BILE ACIDS: AN IMPORTANT FACTOR MODULATING THEIR ABSORPTION

Abstract

Experimental work has shown that less polar bile acids, although better absorbed passively, have a reduced affinity for the ileal transport system and are more extensively adsorbed to residues and microbes. This study examines the fecal excretion of bile acids and the % adsorbed in relationship with the qualitative pattern in 2 categories of patients with an intact ileum. The contaminated small bowel syndrome was diagnosed in 4 cases of chronic idiopathic intestinal pseudoobstruction with fat (19.3 ± 6.8g/24h) and bile acid (693 85mg/m²/24h) malabsorption. Primary bile acids were essentially absent. The sum of deoxycholic, lithocholic, 3-ketocholanoic and 3-betacholanoic acid accounted for 80.3±6.2% of the total. Only a small % (16.7±5.4) of bile acids could be recovered in the aqueous phase. A marked reduction (P < .001) of the anaerobic flora in a fresh stool obtained from 6 CF children on triple I.V. therapy was associated with a reduction in the concentration of secondary forms (P<.005) and with a 5-fold increase (10.2 vs 52.7) in the % of bile acids in the aqueous phase when compared to 7 studied off antibiotics. In 4 CF patients studied both on oral cloxacillin and during I.V. therapy, there was no change in steatorrhea (15.9±5.7 vs 18.8±7.8g/24h) but a large decrease in bile acid loss (751±182 vs 366±93). This study suggests that the extent of microbial transformations of bile acids in the GI tract plays a role on their absorption.

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