Bile acid concentrations in the diagnosis of hepatobiliary disease in the dog

SUMMARY The clinical usefulness of measuring serum bile acid concentrations as a diagnostic test for hepatobiliary disease, was examined in 150 dogs that were suspected of having hepatic disease. Serum values of total bilirubin ( tb ), alkaline phosphatase ( alp ), alanine transaminase ( alt ), and albumin were also measured. Fasting serum bile acid ( fsba ) values were determined, using a solid-phase radioimmunoassay for total conjugated bile acids or a direct enzymatic spectrophotometric method. A definitive diagnosis was established by histologic examination of the liver. On the basis of histologic findings, dogs were assigned to groups (1 to 8, respectively) including: extrahepatic bile duct obstruction, cirrhosis, portal systemic vascular anastomosis ( psva ), hepatic necrosis, intrahepatic cholestasis, steroid hepatopathy, neoplasia, and secondary disease. Dogs in group 8 had no morphologic evidence of hepatobiliary disease or had mild hepatic lesions. Test efficacies of fsba , tb , alp , alt , and albumin were expressed using 4 indices: sensitivity, specificity, and positive-predictive and negative-predictive values. The diagnostic efficacy of fsba was examined alone and in combinations with the other tests. There was wide overlapping of fsba values among dogs in groups 1 to 7, and there was wide overlapping of alt and alp values among dogs in all groups. The specificity of fsba for the diagnosis of liver disease exceeded 90% at values ≥ 30 μmol/L and reached 100% at ≥ 50 μmol/L. Individual liver tests with the best sensitivity for each group were: fsba and alp for extrahepatic bile duct obstruction; fsba for cirrhosis and psva ; alt for hepatic necrosis; and alp for intrahepatic cholestasis, steroid hepatopathy, and neoplasia. Combinations of tests with the best sensitivity for each group were: fsba + alp for extrahepatic bile duct obstruction; fsba + alt for cirrhosis and psva ; fsba + alt and tb + alt for hepatic necrosis; and fsba + alp for intrahepatic cholestasis, steroid hepatopathy, and neoplasia. Individual tests had the best sensitivity. Individual tests with the best positive-predictive value were fsba and tb . The least specific test was alp . The best overall test combination for the detection of hepatobiliary disease was fsba + tb + alt . Adding alp to fsba + tb + alt was never an improvement. Only the group with psva did not benefit from combination testing in which values of fsba alone gave the best sensitivity, specificity, and predictive value. In dogs with liver disease in groups 1,2, and 4 to 7, examined collectively there were significant correlations ( P 30 μmol/L warrant liver biopsy for morphologic diagnosis of hepatobiliary disease.