Liver Biopsy

Indications for performing this procedure:  Liver biopsy is often required to obtain a definitive diagnosis, therefore providing for appropriate treatment and an accurate prognosis in patients with liver disease. 

Contraindications:  

• Coagulopathies:  A biopsy of the liver may be contraindicated if a coagulopathy exists.  One of the functions of the liver is to make clotting factors, thus an animal with diffuse hepatopathy may be at risk for hemorrhage following one of these procedures.  Prothrombin time (OSPT)  and partial thromboplastin time (APTT) should be done to evaluate clotting ability before initiating biopsy on an animal with liver disease.  If clotting times are prolonged, a blood or plasma transfusion to supply clotting factors should be given before proceeding with a biopsy.  There is risk of puncturing the stomach, intestines, or biliary system, which may be reduced by using an ultrasound-guided technique.  

• Anesthesia Risk:  Animals that are not stable enough to be anesthetized should not undergo a wedge biopsy, and may not be adequately stable for a percutaneous biopsy under sedation.  If an animal is not a candidate for either type of biopsy, a fine needle aspirate should be considered.

Types of Biopsies:  Specimens obtained by biopsy are placed in formalin, and submitted for histopathology.  

• Percutaneous core biopsy:  This biopsy provides more information than a fine needle aspirate, as it allows some evaluation of hepatic architecture.  It is more useful in diffuse liver disease than focal disease, as focal lesions may be missed.  The sample obtained from a core biopsy is about 2 cm in length and 0.5 cm in diameter.  Depending on the temperament of the animal, sedation may be required.

• Wedge biopsy:  A wedge biopsy involves surgically removing a portion of liver tissue during a laparotomy.  Wedge biopsies provide the most information, as a larger sample can be taken, and the liver and other abdominal organs can be well visualized during the procedure.  This approach also allows better control of hemorrhage, should it occur.  Wedge biopsies taken during exploratory laparotomy are the method of choice for biopsy when an abscesses or biliary obstruction is suspected.  Disadvantages to this approach are that it is invasive, requires general anesthesia, and is more costly.  Severely debilitated patients may not be good candidates for a procedure requiring general anesthesia. 

Histopathology results for various differentials:  (assuming a diagnostic sample is obtained)

• Hepatic lymphosarcoma:  Characterized by a predominance of immature lymphocytes. 

• Hepatic lipidosis:  Characterized by lipid filled, vacuolated hepatocytes that are increased in size with displaced nuclei.  Oil-red-O stain confirms that the vacuoles are filled with lipid.

• Toxic hepatopathy:  Specific patterns of lesions have been described for certain toxins, though in general toxins cause centrilobular hepatic necrosis to massive generalized hepatic necrosis. 

• Cholangiohepatitis:  Acute, suppurative cholangiohepatitis is characterized by a predominance of neutrophils in and around bile ducts, periportal necrosis of hepatocytes, and degeneration of  bile duct epithelium.  Chronic, non-suppurative cholangiohepatitis has a predominance of lymphocytes as well as neutrophils in and around bile ducts, as well as bile duct proliferation and fibrosis. 

For more information. . .

• Textbook of Veterinary Internal Medicine: Diseases of the Dog and Cat, Ettinger and Feldmen, Chapter 142.