The complexity of canine hepatitis is just beginning to be appreciated and understood. Lack of adequate characterization of these diseases and the temptation to extrapolate directly from medical literature in human patients to say that hepatitis in dogs is identical to those long studied in humans may be preventing more progress being made in veterinary medicine.

Canine hepatitis comprises a spectrum of hepatic diseases that share similar historic, clinical and possibly histopathologic features. Dogs with hepatitis are ill for weeks to months with combinations of anorexia, weight loss, lethargy, polyuria and polydipsia, jaundice, abdominal effusion and hemorrhagic tendencies.

Occasionally, high serum liver enzyme activities are detected during routine evaluation before elective surgery in asymptomatic dogs. In addition, there may be clinically relevant hepatic disorders in which liver enzyme activities are silent but there is other evidence of serious hepatic disease. A liver biopsy is crucial for accurate diagnosis and prognosis, although there is great overlap in histopathologic findings among canine hepatitis.

To better understand the role of the immune system in the development of hepatitis in dogs, studies sought to determine the frequency of serum antibodies directed at cell nuclear material, smooth muscle mitochondria, and liver membrane in 21 and 24 dogs with confirmed hepatitis respectively. These studies have demonstrated the presence of certain autoantibodies in dogs with hepatitis, but the clinical significance of these findings remains to be clarified.