After conjugated bile acids are secreted into the small intestine, what percentage is reabsorbed and where is the main site?

• A. 70%, Jejunum
• B. 90%, Ileum
• C. 50%, Duodenum
• D. 100%, Ileum

Answer: (B)

Bile acids follow enterohepatic circulation, where after being secreted into the small intestine the vast majority are reabsorbed and returned to the liver. The terminal ileum is the primary site for this reabsorption of conjugated bile acids. About 90% are reabsorbed, helping to recycle bile acids efficiently and maintain the hepatic bile acid pool. In the ileal enterocytes, the apical transporter ASBT brings bile acids into the cell, and the basolateral OSTα/β moves them into the portal circulation for return to the liver, where uptake occurs again by hepatic transporters. If ileal reabsorption is impaired, more bile acids reach the colon, causing diarrhea and a drop in bile acid pool, which the liver may compensate for by increasing synthesis.

So, the best answer reflects that roughly 90% are reabsorbed, primarily in the ileum. The jejunum and duodenum reabsorb only a minority in comparison, and 100% reabsorption would be incorrect because a portion is normally lost in feces.