Bactibilia in Extrahepatic Biliary Obstruction: Does Etiology Influence Bacterial Growth?

Background: Extrahepatic biliary obstruction (EHBO) predisposes to bactibilia due to impaired bile flow and increased intraductal pressure. While benign etiologies are traditionally associated with higher rates of bile infection, malignant biliary obstruction is often presumed to be sterile. Available evidence is conflicting and largely retrospective, with limited prospective data from the Indian subcontinent. Methods: This prospective observational study included consecutive patients aged 18–65 years undergoing first-time ERCP for EHBO at two tertiary care centers in India between March 2018 and February 2021. Bile was aspirated aseptically prior to contrast injection and cultured using automated blood culture systems. Patients were categorized into benign and malignant obstruction groups. Culture positivity, growth patterns, and organism distribution were compared between groups. Results: A total of 204 patients were included (benign: n=144; malignant: n=60). Overall, bile cultures were positive in 63.7% of patients. Culture positivity was significantly higher in benign obstruction compared to malignant obstruction (69.4% vs 50.0%, p=0.01). Polymicrobial growth was observed exclusively in benign obstruction (20.1%), whereas all malignant cases demonstrated monomicrobial growth. Among 153 bacterial isolates identified, Escherichia coli was the most common organism, followed by Klebsiella spp., Enterococcus spp., and Pseudomonas spp. The distribution of bacterial isolates did not differ significantly between benign and malignant obstruction (p>0.05). Conclusion: Bactibilia is common in EHBO and occurs more frequently in benign disease; however, malignant biliary obstruction is not invariably sterile. While growth patterns differ by etiology, the bacterial spectrum remains similar. These findings highlight the need for vigilance regarding biliary infection in both benign and malignant EHBO, particularly during endoscopic intervention.