Extrahepatic biliary atresia in a border collie

Progressive lameness and leg pain were the predominant clinical signs in a 17-week-old male border collie presented for examination. On clinical inves tigation, extrahepatic cholestasis in association with rickets due to inade quate vitamin D resorption was diagnosed. The dog was treated parenterally with vitamin D and a cholecystoduodenostomy was performed. At 25 days posts urgery the lameness had resolved and bone structure was radiographically no rmal. However, at six weeks postsurgery, the dog's condition deteriorated r apidly and euthanasia was finally performed at eight weeks postsurgery. At postmortem examination, Toxocara canis nematodes were found to have invaded the biliary system via the anastomosis between the gallbladder and duodenu m, causing biliary and hepatic toxocariasis. The cause of the primary extra hepatic cholestasis was atresia of the common bile duct at the hepatic end. The liver tissue showed microscopic lesions of chronic extrahepatic choles tasis as well as acute inflammation associated with the nematode invasion. There was no postmortem evidence of bone lesions. Extrahepatic biliary atre sia is extremely rare in animals and has not been described before in dogs. In contrast, it represents the most common cause of congenital cholestasis in children, occurring in approximately one per 10,000 to 15,000 live birt hs.