Pressure relationships within the human bile tract. Normal and abnormal physiology.

Bile is secreted continuously, although at various rates, from the liver into the biliary tree; whether bile is then diverted into the gallbladder or the duodenum depends on the relative resistance to flow mainly determined by the contractile state of the gallbladder and the choledochoduodenal junction. The resistance of the sphincter of Oddi is considered the principal factor in the regulation of the intracholedochal pressure and, therefore, of the common bile duct-gallbladder pressure gradient; however, filling of the gallbladder may also take place after total sphincterotomy. During late phase II of the interdigestive period intragallbladder pressure increments favour flow of a small amount of bile into the bile duct and, through the sphincter of Oddi, into the duodenum. During phase III of the interdigestive period maximal frequency of sphincter of Oddi phasic contractions blocks bile flow into the duodenum. After a meal tonic active contraction of the gallbladder causes an increase of the intraluminal pressure followed shortly by volume reduction of the viscus and outflow of bile accompanied by an intracholedochal pressure increment. Gallbladder hypotonia is a relevant factor in the pathogenesis of gallbladder stones. The gallbladder acts as a reservoir, since intracholedochal pressure is higher after than before cholecystectomy, and this may explain post-cholecystectomy choledochal dilatation and biliary pain by obstructed bile flow due to either stenosis or dyskinesia of the sphincter of Oddi.