A 2.5-year-old spayed female Jack Russell Terrier was referred for surgical attenuation of a single congenital extrahepatic portosystemic shunt that had been detected via abdominal ultrasonography. The dog had a history of intermittent vomiting, pacing, and destructive behavior with acute exacerbation immediately prior to initial evaluation by the referring veterinarian. Preprandial (180 μmol/L; reference range, 0 to 12 μmol/L) and postprandial (246 μmol/L; reference rage, 0 to 16 μmol/L) serum bile acids concentrations were high, and serum biochemical analysis revealed hypoproteinemia (5.3 g/dL; reference range, 5.4 to 7.6 g/dL) and hypocholesterolemia (77 mg/dL; reference range, 135 to 361 mg/dL).