- Biliary obstruction or stasis
- Primary initiating factor in most cases
- Common causes:
- Biliary strictures (e.g. post-surgical, PSC, anastomotic)
- Choledocholithiasis or sludge
- Biliary-enteric anastomoses or altered anatomy (e.g. Roux-en-Y)
- Tumours (e.g. cholangiocarcinoma, pancreatic head mass)
- Consequences:
- Impaired bile drainage
- Increased intraductal pressure
- Promotes bacterial colonisation and infection
- Bacterial contamination of bile
- Normally sterile bile becomes infected via:
- Ascending infection from the duodenum (especially with sphincterotomy or stents)
- Iatrogenic introduction during ERCP or surgery
- Haematogenous spread via the portal vein
- Common organisms:
- Gram-negatives: E. coli, Klebsiella, Enterobacter
- Gram-positives: Enterococcus
- Anaerobes and fungi (especially with indwelling stents)
- Impaired local defences
- Bile salts normally exert bacteriostatic effects and flush pathogens
- Obstruction leads to:
- Reduced bile salt concentration
- Impaired mechanical clearance of bacteria
- Favourable conditions for biofilm formation (on stones or stents)