Bile duct carcinoma
These tumors commonly arise from intrahepatic bile ducts resulting in intrahepatic biliary obstruction. An underlying exposure to carcinogens or liver flukes can predispose to development of these tumors.
Bile duct carcinomas are commonly locally invasive and aggressive metastasize in up to 80% of dogs to the lungs, lymph nodes of the liver and peritoneum.
Some bile duct carcinomas are known as cystadenocarcinomas because they contain dilated cystic spaces with columnar to cuboidal epithelium with a mucin content.
Diagnosis can be difficult but can be achieved with blood tests (often shows hypoalbuminemia and elevated liver enzyme; ALP, GGT, conjugated bilirubin and cholesterol, indicative of cholestasis), ultrasonography, urinalysis and CT imaging.
A clotting function test should also be performed.
Radiographically, there is usually loss of intraperitoneal detail due to effusion or intraperitoneal seeding of the tumor. Hepatomegaly is also a common finding.
Contrast-enhanced ultrasonography offers a more precise method of detecting the site of origin of an abdominal mass and may be used as a guide to obtain fine-needle aspirates or for preoperative liver biopsy.
On exploratory laparotomy, some extrahepatic biliary duct carcinomas may appear as dilated mucus-filled structures rather than well-circumscribed masses.
Histologically, these tumors may be well differentiated or poorly differentiated. Intrahepatic bile duct proliferation (ductular reaction) is a common finding, as well as neoplastic changes to ductular epithelium.
Treatment is restricted to chemotherapy such as doxorubicin or regional cryoablation as palliative tools as these tumors have a guarded to poor prognosis and have frequently metastasized by the time of diagnosis.
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