Physiological basis of enterohepatic recycling in the dog.

Numerous compounds either endogenous (biliary salts, hormones, vitamines), or drugs, are absorbed from the gut after their excretion via the biliary r oute. This phenomenon was discovered with the biliary salts and was called enterohepatic recycling. It implies different physiologic steps as hepatic metabolism and excretion, biliary transit with or without gallbladder stora ge, continous or discontinous arrival of bile in the duodenum, transit of b ile from the duodenum to the ileum, intestinal bacterial metabolism,and abi lity of the different part of the intestine for absorption. These different events depend on time and are in relation with other physiologic events. F or exemple, time of gallbladder emptying depends of alimentary status (fast ing or feeding) and is in relation with intestinal pattern of motility. Thu s, reabsorption of compounds excreted on a conjugated form in the bile depe nds of intestinal environment. The different steps of this cycle are presen ted in the dog.