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**'''Gall bladder mucocoeles''' produce a kiwi sign on radiographs and may be a sequel to cystic mucinous hyperplasia of the gall bladder mucosa.
**'''Gall bladder mucocoeles''' produce a kiwi sign on radiographs and may be a sequel to cystic mucinous hyperplasia of the gall bladder mucosa.
**'''Biliary neoplasia''', most commonly cholangiocellular cystadenoma (in cats) or carcinoma (in dogs).
**'''Biliary neoplasia''', most commonly cholangiocellular cystadenoma (in cats) or carcinoma (in dogs).
**'''Aberrant migration of intestinal helminths''' may cause an obstruction if they enter the common bile duct. This has been reported with ''[[Ascaris suum]]'' in pigs and ''[[Parascaris equorum]]'' in horses and it may occur after these animals have been treated with an anthelmintic that causes spasticity of the parasite muscles.
*Extraluminal obstructions:
*Extraluminal obstructions:
**[[Pancreatitis - Dog and Cat|'''Pancreatitis''']] is the most common cause of obstruction in dogs. '''Pancreatic abcesses''' or '''neoplasia''' may also obstruct the flow of bile.
**[[Pancreatitis - Dog and Cat|'''Pancreatitis''']] is the most common cause of obstruction in dogs. '''Pancreatic abcesses''' or '''neoplasia''' may also obstruct the flow of bile.
**'''Diaphragmatic rupture''' with herniation of parts of the liver may result in exertion of pressure on the biliary tract.
**'''Diaphragmatic rupture''' with herniation of parts of the liver may result in exertion of pressure on the biliary tract.
**'''Biliary pseudocysts''' are a rare cause of obstruction.
**'''Biliary pseudocysts''' are a rare cause of obstruction.
==Diagnosis==
==Diagnosis==
'''Vomiting''' and '''anorexia''' are the most common signs of biliary obstruction.
'''Vomiting''' and '''anorexia''' are the most common signs of biliary obstruction.
The failure to excrete [[Bilirubin|bilirubin]] results in an increase in the blood concentration of conjugated bilirubin. Beyond a certain level, this bilirubin stains tissues causing [[Icterus|jaundice]] which may be visible on the mucous membranes or sclera. Since bilirubin has a low renal threshold, high concentrations are found in urine, although bilirubinuria is not necessarily an abnormal finding in healthy animals. In a complete biliary obstruction, [[Bilirubin|urobilinogen]] will also be absent from the urine.
The failure to excrete [[Bilirubin|bilirubin]] results in an increase in the blood concentration of conjugated bilirubin. Beyond a certain level, this bilirubin stains tissues causing [[Icterus|jaundice]] which may be visible on the mucous membranes or sclera. Since bilirubin has a low renal threshold, high concentrations are found in urine, although bilirubinuria is not necessarily an abnormal finding in healthy animals.
Biliary obstruction results in a reduction in the normal function of the hepatic monocyte-phagocyte system (chiefly composed of Kupffer cells) and the absence of bile salts allows intestinal bacteria to proliferate. Affected animals are not able to remove bacteria from the portal blood with normal efficiency and they may suffer systemic bacterial infection, causing sepsis, polyarthritis, endocarditis, meningitis or uveitis.
Biliary obstruction results in a reduction in the normal function of the hepatic monocyte-phagocyte system (chiefly composed of Kupffer cells) and the absence of bile salts allows intestinal bacteria to proliferate. Affected animals are not able to remove bacteria from the portal blood with normal efficiency and they may suffer systemic bacterial infection, causing sepsis, polyarthritis, endocarditis, meningitis or uveitis.