Background: Antibiotic treatment of cholangitis often remains insufficient due to inappropriate antibiotic use or bacterial resistance.

Objective: To evaluate the role of routine bile collection during endoscopic retrograde cholangiography (ERC) or percutaneous transhepatic cholangiography (PTC) for microbiological analysis in the antibiotic management of cholangitis and to identify risk factors of microbial growth.

Design: Prospective, observational, diagnostic study.

Setting: Hannover Medical School, Hannover, Germany. Patients and Interventions: Consecutive patients undergoing ERC/PTC for biliary complications after orthotopic liver transplantation , malignancy, primary sclerosing cholangitis, benign strictures and choledocholithiasis.

Main outcome measurements: Microbiological examination of bile samples

Inclusion Criteria:

• age above 18 years
• written informed consent

Exclusion Criteria:

• age under 18 years
• no written informed consent

patients presenting to Endoscopic retrograde cholangiography