Cholangiocarcinoma: Consistent clinical, cytological, hematological, and biochemical findings and pathomorphology of the liver and kidney in five exotic dog breeds in Abeokuta, Nigeria.

Background and aim: Cholangiocarcinomas are malignant neoplasms that originate from any part of the bile duct epithelium. It is one of the most common liver tumors in dogs. This study described the clinical, cytological, hematological, biochemical, and pathomorphological findings of five cholangiocarcinoma cases in exotic breed dogs aged 2-5 years to aid in clinical diagnosis.

Materials and methods: This study used dogs presented at different times from 2012 to 2021 at the Veterinary Teaching Hospital, Federal University of Agriculture, Abeokuta. History, clinical signs, and vital parameters were recorded. Blood samples were collected for hematology and serum chemistry. Abdominocentesis was performed for cytological diagnosis. All dogs died during treatment, and postmortem examinations were performed. At postmortem, fine needle aspirates were collected from the liver and mesenteric lymph nodes and liver and kidney samples were fixed in 10% neutral-buffered formalin.

Results: The dogs showed signs of severe malnutrition, jaundice, and bloating. The hematological analysis indicated anemia, neutrophilia without band neutrophils, and lymphopenia, indicative of a stress hemogram. The serum biochemistry test revealed lower levels of total proteins, albumin, and globulin and higher levels of serum enzymes. Abdominal fluid and mesenteric lymph node cytology revealed clusters of epithelial neoplastic cells. A postmortem examination revealed the liver's nodular enlargement with the presence of button-like ulcers. Neoplastic epithelial cells are solid masses with hyperchromatic nuclei surrounded by fibrous connective tissues.

Conclusion: Cholangiocarcinoma, diagnosed over a period of time in five exotic breeds of dog, consistently presents with the same clinical and postmortem findings, aiding in clinical diagnosis. However, the diagnosis of the disease is not possible in the early stage because of the absence of specific clinical signs. In dogs and possibly other animal species presenting with emaciation, lethargy, icterus, and distended abdomen, cholangiocarcinoma should be suspected, and cytological examination of the abdominal fluid and lymph node aspirates should be performed despite the absence of advanced equipment.