A Pilot Study of Vancomycin or Metronidazole in Patients With Primary Sclerosing Cholangitis

Inclusion Criteria: * Diagnosis of PSC established by alkaline phosphatase \>1.5 times and/or two fold elevation of liver transaminases (AST and/or ALT) for at least 6 months duration. * Cholangiography demonstrating intrahepatic and/or extrahepatic biliary obstruction, beading, or narrowing consistent with PSC. * Both genders. * Age ≥ 18 years old and \< than 75 years old. * Patient's informed consent for study participation. Exclusion Criteria: * Treatment with systematic antibiotics, azulfidine, ursodeoxycholic acid, corticosteroids, colchicine, methotrexate, azathioprine, cyclosporine, chlorambucil, budesonide, pentoxifylline, tacrolimus, silymarin or prednisone in the preceding three months. * Active drug or alcohol use. * Prior history of allergic reactions to the antibiotics which will be used in the study. * Any condition that, in the opinion of the investigator, would interfere with the patients' ability to complete the study safely or successfully. * Evidence of decompensated liver disease such as recurrent variceal bleeding, refractory ascites or spontaneous hepatic encephalopathy. * Anticipated need for transplantation in one year (Mayo survival model \<80% one-year survival without transplant). * Findings highly suggestive of liver disease of other etiology such as chronic alcoholic liver disease, chronic hepatitis B or C infection, hemochromatosis, Wilson's disease, 1-antitrypsin deficiency, non-alcoholic steatohepatitis, primary biliary cirrhosis or secondary sclerosing cholangitis. * Pregnancy or current lactation. Subjects becoming pregnant during the study will be withdrawn.