Feline inflammatory liver disease - an overview (part 1)
In the broadest terms, conditions affecting the feline liver may be divided into inflammatory and non-inflammatory diseases. Unlike dogs, where inflammatory conditions tend to affect the hepatic parenchyma, in cats the biliary system is more commonly affected, with extension into the hepatic parenchyma only in more severe cases. As a result, cats with hepatic disease will frequently present with jaundice (Figure 1) but rarely develop a small cirrhotic liver hence; with the exception of portosystemic shunts, the finding of a small liver is unusual in the feline patient. It should also be remembered that the liver may be affected by systemic diseases such as feline infectious peritonitis (FIP). This article reviews the complex group of disorders that is feline inflammatory liver disease. Out with the scope of this article, but mentioned where appropriate when considering differential diagnosis, are the non-inflammatory conditions, the most important of which is hepatic lipidosis (HL). Other non-inflammatory causes include liver neoplasia, portosystemic shunts, amyloidosis, and polycystic liver disease.
Inflammatory liver disease
Given that feline inflammatory liver disease more typically affects the biliary system it should more correctly be called cholangitis, and in the UK cholangitis is the most commonly identified feline liver disorder. Different forms of cholangitis may be identified by histopathology of liver biopsies. Unfortunately, numerous different terminologies have been used over the years in the veterinary literature, hence the WSAVA have produced guidelines in an attempt to standardize the diagnosis (1).
The cholangitis complex comprises lymphocytic cholangitis (LC), neutrophilic cholangitis (NC), and chronic cholangitis associated with liver fluke (1). Mild lymphocytic portal hepatitis should not be over-interpreted as it is believed to be a nonspecific reactive change possibly reflecting extrahepatic disease or resolving hepatitis: >80% of cats over 10 years of age were reported to have these mild changes in one study (2).
Previously termed non-suppurative or lymphocytic-plasmacytic cholangitis/cholangiohepatitis, the etiology of this condition is not known but an immune-mediated mechanism may play a role.
Cats of any age may be affected, but disease is seen most typically in young to middle aged cats; Persian cats may have an increased risk (3). Clinical signs are usually chronic and insidious in nature, but may be acute. Affected cats are typically jaundiced, but appear to be clinically well, and are often polyphagic. Weight loss may be seen, despite a good appetite. Anorexia can also be seen, as can vomiting and/or diarrhea. Cats may have a palpably enlarged liver, and enlarged mesenteric lymph nodes; mild generalized lymphadenopathy may also be present. The disease may progress to causing chronic biliary cirrhosis with ascites, hepatic encephalopathy, and bleeding tendencies. Ascites may be present – in acute cases due to a hepatic exudate (which can make this condition difficult to differentiate from wet FIP), and in chronic cases from portal hypertension resulting from periportal fibrosis and cirrhosis.
Serum biochemistry often reveals mild/moderately (occasionally severely) increased liver enzymes, increased bile acids, hyperbilirubinemia, hyperglobulinemia, and hypoalbuminemia. Hematology may reveal mild anemia, lymphopenia or lymphocytosis, monocytosis, and/or thrombocytopenia. Blood clotting times are frequently prolonged. Ascitic fluid, if present, is typically high in protein. Ultrasound examination may show heterogeneous hepatic parenchyma, which is often hyperechoic. Histopathology typically shows periportal lymphocytic infiltration. Portal fibrosis and proliferation of biliary ductules may also be seen.
Differential diagnoses in a cat presenting with some or all of the above signs are numerous and are summarized in Tables 1-3. The primary possibilities to consider would be FIP (especially if ascites is present), NC, hepatic lipidosis (HL), lymphoma, and if weight loss with a good appetite is present, hyperthyroidism or exocrine pancreatic insufficiency.
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This article was kindly provided by Royal Canin, makers of Hepatic dry diet for cats. For the full range please visit www.RoyalCanin.co.uk or speak to your Veterinary Business Manager:
1. WSAVA Liver Standardization Group. WSAVA Standards for Clinical and Histological Diagnosis of Canine and Feline Liver Diseases. Philadelphia: Saunders Elsevier, 2006; 68-71.
2. Weiss DJ, Gagne JM, Armstrong PJ. Characterization of portal lymphocytic infiltrates in feline liver. Vet Clin Pathol 1995; 24: 91-95.
3. Lucke VM, Davies JD. Progressive lymphocytic cholangitis in the cat. J Small Anim Pract 1984; 25: 249-260.
4. Greiter-Wilke A, Scanziani E, Soldati S, et al. Association of Helicobacter with cholangiohepatitis in cats. J Vet Intern Med 2006; 204: 822-827.
5. Weiss DJ, Gagne JM, Armstrong PJ. Relationship between inflammatory hepatic disease and inflammatory bowel disease, pancreatitis, and nephritis in cats. J Am Vet Med Assoc 1996; 209: 1114-1116.
6. Gagne JM, Armstrong PJ, Weiss DJ, et al. Clinical features of inflammatory liver disease in cats: 41 cases (1983-1993). J Am Vet Med Assoc 1999; 214: 513-516.