What are the causes of liver abscess?

Causes of Liver Abscess

Primary Etiologic Categories

Liver abscesses arise from two main infectious etiologies: pyogenic (bacterial) and parasitic (primarily amebic), with distinct pathophysiologic mechanisms and geographic distributions. 1, 2

Pyogenic (Bacterial) Liver Abscess

Pyogenic liver abscesses are the predominant type in Western countries and result from bacterial contamination of liver parenchyma through several distinct routes 1:

Biliary Tract Sources (Most Common)

• Biliary disease is the most common underlying cause of pyogenic liver abscess 2
• Cholecystitis and cholangitis from gallstone disease 1
• Biliary obstruction with ascending infection 3
• Post-procedural cholangiolytic abscesses following ERCP or sphincterotomy 4
• Bile duct ischemia secondary to pancreatoduodenectomy or liver transplantation 1

Intra-abdominal Infections (Portal Venous Route)

• Appendicitis with portal pylephlebitis 5, 1
• Sigmoid diverticulitis 1
• Crohn's disease with transmural inflammation, including direct extension of intra-abdominal abscesses or fistulizing disease 5, 1
• Other infections in the portal venous drainage area 3

Hematogenous Spread (Arterial Route)

• Systemic septicemia seeding the liver, typically with Staphylococci or Streptococci 3
• Klebsiella pneumoniae bacteremia with increasing incidence, which can cause distant septic metastases 1
• Dental procedures with hematogenous seeding 4

Direct Extension and Iatrogenic Causes

• Radio-frequency ablation of liver lesions 1
• Intra-arterial chemoembolization 1
• Liver trauma 1
• Infection of preexisting liver lesions (biliary cysts, hydatid cysts, cystic or necrotic metastases) 1

Microbiology Patterns

• Mixed flora with gram-negative aerobes and anaerobic bacteria in portal venous or traumatic abscesses 3
• Gram-negative organisms in biliary-origin abscesses 3
• Staphylococci or Streptococci in hematogenous spread 3

Amebic Liver Abscess

Amebic liver abscess is caused by extraintestinal spread of Entamoeba histolytica and is the most frequent cause in South-East Asia and Africa 1, 2:

• Fecal-oral transmission with initial gastrointestinal colonization 2
• Hematogenous spread from intestinal infection to liver parenchyma 2
• More common in subtropical and tropical climates with poor sanitation 6
• Sporadically observed in non-endemic regions after travel 3

Less Common Etiologies

• Fungal abscesses are very rare 1
• Secondary hepatic amyloidosis complicating inflammatory bowel disease (0.9% in Crohn's disease, 0.07% in ulcerative colitis) 5
• Granulomatous hepatitis in IBD patients 5

Important Clinical Pitfalls

• Chronic enteric biliary contamination (sphincterotomy, bilioenteric anastomosis) increases risk before radio-frequency ablation or chemoembolization 1
• Substantial celiac trunk stenosis should be detected before pancreatoduodenectomy to prevent iatrogenic abscess formation 1
• Portal vein thrombosis is a severe complication more frequent in the postoperative setting in IBD patients 5
• Mortality remains high at approximately 15% for pyogenic abscesses, primarily due to patient debilitation and persistence of the underlying cause 1