hepatic cirrhosis

Introduction: Hepatic fibrosis and regenerative nodules characterize hepatic cirrhosis. Chronic injury to the liver elicited by a wide variety of causes can lead to an "end stage liver". Insults include chronic or repetitive exposure to a toxin or drug, infection, cholangiohepatitis (especially cats), immunologic injury, and hypoxia. A single event of massive hepatic necrosis (post-necrotic cirrhosis), although it is less common, can also lead to end stage liver disease. The incidence of cirrhosis is unknown in dogs. Cirrhosis in cats is usually secondary to cholangiohepatitis or extrahepatic biliary obstruction. This form of cirrhosis is characterized as biliary cirrhosis.

Pathogenesis: Hepatocyte death is the common contributing factor to all causes of cirrhosis. Hepatocellular death causes reparation by fibrosis and regeneration of hepatocytes. The regenerative hepatocytes form nodules that are structurally disorganized, and have diminished blood flow due to their lack of normal cellular structure between hepatocytes and blood vessels. This diminished flow causes the continuing cycle of cell death, hyperplasia and fibrosis, thus perpetuating the problem. Fibrous tissue is formed more quickly than it can be removed, thus causing an overall increase in collagen content of the liver. The process of repair ends up compromising adjacent normal hepatocytes, intrahepatic vascularization and bile flow.

Hepatic blood flow is compromised due to increased hepatic vascular resistance caused by fibrosis and vascular compression from the regenerative nodules. Increased hepatic vascular resistance contributes to the clinical signs of ascites, multiple acquired extrahepatic portosystemic shunts, and hepatic encephalopathy. Cirrhosis eventually becomes a self-perpetuating problem.

Gross Pathology: In dogs, the cirrhotic liver is smaller than normal (microhepatica). The liver is firm and the process is, by definition, diffuse. The liver appears nodular because of the regenerative nodules surrounded by dense bands of fibrous tissue. In cats, the liver may be enlarged in cirrhosis.

Micronodular cirrhosis in a dog: Note the small nodules of regeneration especially to the left. This liver is more firm than normal due to fibrosis.

Click on the images for a larger view and more information.

Macronodular cirrhosis in a Doberman Pinscher.
Note the large nodules of regeneration. The surrounding tissue is firm.

Click on the image for a larger view.

Histopathology: The pattern of fibrosis seen histologically will depend upon the cause of hepatocellular injury. Many times a pattern is not (or is no longer) detectable.

Portal fibrosis (biliary fibrosis) and parenchymal nodules are associated with chronic inflammation or other processes that are centered on bile ductules. It is commonly seen in cats with cholangiohepatitis or in dogs with chronic hepatitis.

Click on image for a larger view and more information.

Periacinar fibrosis is centered around central veins. It may be seen with chronic passive congestion secondary to right-sided heart failure or with certain toxins.

Click on image for a larger view and more information.

Species affected: Cats, dogs, horses, and ruminents can have hepatic cirrhosis.


Cats	Horses	Dogs	Ruminants

Clinical signs: Sometimes the signs are vague and nonspecific (i.e. anorexia, lethargy, vomiting, polyuria, and polydipsia). Increased severity of hepatic failure may present with signs of icterus, ascites, coagulopathy, and hepatic encephalopathy. Onset of signs can be acute as well as chronic. Chronic disease may present acutely.

Hepatic Cirrhosis