Pathologic Changes in Bile in Small Animals

In animals with bile stasis, nonabsorbable bile constituents (bile salts, phospholipids, glycoproteins, and cholesterol) are subject to concentration or dilution when water and inorganic electrolytes (sodium, chloride, bicarbonate) are resorbed or added by the biliary epithelium. EHBDO can produce a “white bile” syndrome reflecting the absence of bilirubin pigments; this usually is found in animals with an obstructed gallbladder at the level of the cystic duct or in animals with obstruction of the hepatic ducts. Stasis of bile flow also may cause bile dehydration, promoting a pathologically thickened or sludged bile typically dark green to black in color. Formation of a gallbladder mucocele involves the entrapment, retention, dehydration, and local overproduction of mucin that lends a rubbery viscosity to bile. Bile stasis in obstructed ducts can lead to bilirubin deconjugation, which reduces bilirubin solubility and favors cholelith precipitation. Choleresis (enhanced bile flow) produces “watery,” dilute bile and is a therapeutic goal in disorders associated with bile stasis.