The cause of chronic hepatitis (CH) in dogs is poorly understood, and an increased incidence of CH has been reported in Labrador retrievers.A veterinary teaching hospital's records of 24 dogs from 2000 to 2005 were reviewed to evaluate CH in this breed. A clinical scoring system was devised based on one used in human medicine to predict survival of CH patients. CH was found to occur in middle-aged to older dogs (median age 9.3 years). Clinical signs included inappetence, vomiting, lethargy, and weight loss, although 17% of the dogs showed no signs other than increases in liver enzymes. All dogs had elevated liver enzymes. Hyperbilirubinemia was found in 45% and hypoalbuminemia in 21%. Most dogs (87%) had some ultrasonographic changes in the liver, but these were largely nonspecific. Hepatic biopsy revealed significant liver disease in all dogs; however, neither histologic stage nor grade was correlated with survival time. No potential cause was found, although a genetic predisposition is suggested based on the breed association. Mild-to-moderate copper accumulation was noted in 15 of 17 biopsy specimens, but whether this is a cause or an effect of CH requires further investigation. Median survival time of these dogs was 374 days. Several variables were associated with survival, including prolonged prothrombin time and thrombocytopenia, which were associated with survival < 2 months; and the presence of anorexia, hypoglobulinemia, or prolonged partial thromboplastin time,which were associated with shorter overall survival time. The clinical score correlated with survival time and might serve as a useful prognostic indicator.

COMMENTARY: This small, retrospective study has limitations but describes breed-related, chronic hepatitis in Labradors based on histologic and clinical scoring systems. Specific etiologies and mechanisms for CH in Labradors are not yet clear, but thorough diagnostic testing (to include hepatic biopsy) in suspect dogs should be performed to best guide the clinician in patient management.

Chronic hepatitis in Labrador Retrievers: Clinical presentation and prognostic factors. Shih JL, Keating JH, Freeman LM,Webster CRL. J VET INTERN MED 21:33-39, 2007.