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The causes of biliary tract obstruction may be '''intraluminal''' or '''extraluminal''':

The causes of biliary tract obstruction may be '''intraluminal''' or '''extraluminal''':

*Intraluminal obstructions:

<u>Intraluminal obstructions:</u>

**'''Choleliths''' ('gall stones') are much less common in animals than they are in humans.  They are usually composed of bilirubin salts in dogs and calcium carbonate in cats, although they are very rare in the latter species.

*'''Choleliths''' ('gall stones') are much less common in animals than they are in humans.  They are usually composed of bilirubin salts in dogs and calcium carbonate in cats, although they are very rare in the latter species.

**'''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.

*'''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:

<u>Extraluminal obstructions:</u>

**[[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.

**[[Biliary Tract - Rupture|'''Biliary tract rupture''']]

*[[Biliary Tract - Rupture|'''Biliary tract rupture''']]

**'''Pyloric''' or '''duodenal mass'''

*'''Pyloric''' or '''duodenal mass'''

**'''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==

The signs of biliary obstruction relate to the failure of bile to move into the small intestine and to the reduction in function of the hepatic monocyte-phagocyte system.

The signs of biliary obstruction relate to the failure of bile to move into the small intestine and to the reduction in function of the hepatic monocyte-phagocyte system.

===Clinical Signs===

===Clinical Signs===

'''[[Vomiting]]''' and '''anorexia''' are the most common signs of biliary obstruction.

'''[[Vomiting]]''' and '''anorexia''' are the most common signs of biliary obstruction.

[[Category:Gall_Bladder_and_Tract_-_Pathology]]

[[Category:Gall_Bladder_and_Tract_-_Pathology]]

[[Category:To_Do_-_James]]

[[Category:To_Do_-_James]]

[[Category:Dog]][[Category:Cat]][[Category:Horse]][[Category:Cattle]][[Category:Pig]]

[[Category:Dog]][[Category:Cat]][[Category:Cattle]][[Category:Pig]]

[[Category:To_Do_-_Review]]

[[Category:Expert_Review]]

[[Category:Alimentary_Disorders_-_Horse]]