Liver disease is a frequently encountered chronic disease process in companion animals. Chronic liver disease is defined as any hepatopathy that has been present for more than 6 to 8 weeks. Common causes include chronic active hepatitis, copper storage hepatopathy, and drug-induced hepatopathy. A larger but more complex group of hepatopathies are those related to infectious, inflammatory, and immune-mediated disease processes. Anorexia, vomiting, weight loss, polyuria/polydipsia, distended abdomen, behavioral changes, and stranguria are common presenting signs. Pertinent physical examination findings include hepatomegaly, jaundice, ascites, abdominal pain, pyrexia, and coagulopathies.
The initial step in evaluating patients suspected of having chronic hepatopathy includes a complete blood count, chemistry panel, and urinalysis. Changes on the complete blood count are often nonspecific and may include mild normocytic normochromic nonregenerative anemia, leukocytosis, and alteration in platelet count.
Valuable information can be gathered from the degree of enzyme elevations and evaluation of synthetic liver products, such as albumin, cholesterol, and blood urea nitrogen. Biliary diseases tend to manifest with elevations in alkaline phosphatase, α-glutamyltransferase, and cholesterol, whereas chronic hepatopathies generally have greater elevations in alanine aminotransferase and aspartate aminotransferase.
Urinalyses often reveal isosthenuria, bilirubinuria, and ammonium biurate crystals. Bilirubinuria may be detected before the development of jaundice. Bilirubinuria can be normal in dogs but is always pathologic in the cat.