What are all the causes of liver abscess?

Causes of Liver Abscess

Pyogenic (Bacterial) Liver Abscess

Gram-negative organisms, particularly Escherichia coli and Klebsiella pneumoniae, are the most frequent bacterial causes of pyogenic liver abscess, with Klebsiella showing increasing incidence worldwide. 1

Primary Bacterial Pathogens

• Gram-negative bacilli constitute the predominant bacterial isolates, with E. coli being most common, followed by Klebsiella pneumoniae which harbors specific virulence factors in hypervirulent clones that are spreading globally 1, 2

• Gram-positive organisms including Staphylococcus and Streptococcus species (particularly abscess streptococci) are important secondary causes 1, 2

• Anaerobic bacteria frequently contribute to polymicrobial infections, reflecting gut flora translocation through biliary or portal routes 1, 2

• Polymicrobial infections are common, especially when the source involves biliary disease or portal vein seeding from intra-abdominal infections 1

Uncommon Bacterial Causes (Context-Specific)

• Pseudomonas aeruginosa, Staphylococcus aureus, and Candida species occur only in specific clinical contexts such as immunosuppression or nosocomial infection 2

• Salmonella species should be considered in immunocompromised patients, particularly those with hematologic malignancies 3

Parasitic Liver Abscess

In endemic regions (South-East Asia, Africa, tropical/subtropical areas with poor sanitation), Entamoeba histolytica is the most common cause of hepatic abscess, transmitted via the fecal-oral route with subsequent hematogenous spread to the liver. 1

Amebic Abscess

• Entamoeba histolytica colonizes the gastrointestinal tract and spreads extraintestinally to the liver, causing amebic liver abscess 1, 4

• This parasitic cause predominates in South-East Asia, Africa, and regions with poor sanitation 1

• Amebic abscesses can occur sporadically in non-endemic regions after travel 5

Echinococcal (Hydatid) Disease

• Echinococcal cysts can become secondarily infected or leak, and should be considered in patients from the Middle East, Central Asia, and the Horn of Africa 1

Fungal Causes (Rare)

• Mycobacteria species, Nocardia species, and other fungal organisms cause hepatic abscesses almost exclusively in immunosuppressed hosts 1

• Fungal liver abscesses are very rare and typically occur in severely immunocompromised patients 6

Mechanisms and Underlying Conditions Leading to Abscess Formation

Biliary Tract Disease (Most Common in Western Countries)

• Biliary obstruction from gallstones, cholecystitis, and cholangitis is the most common underlying cause of pyogenic liver abscess in Western populations 6, 4

• Bile duct ischemia secondary to pancreatoduodenectomy, liver transplantation, or interventional procedures (radiofrequency ablation, intra-arterial chemoembolization) can lead to abscess formation 6

• Post-procedural cholangiolytic abscesses can develop after ERCP, sphincterotomy, or bile duct injury 3

Portal Vein Seeding

• Intra-abdominal infections including appendicitis, sigmoid diverticulitis, and Crohn's disease can seed the liver via the portal vein 6

• Portal pylephlebitis (septic thrombophlebitis of the portal vein) is a recognized mechanism 7

Direct Extension

• Direct extension from intra-abdominal abscesses or fistulizing disease (particularly in inflammatory bowel disease) can cause hepatic abscess 7

• Liver trauma can result in secondary abscess formation 3

Hematogenous Spread

• Systemic septicemia can seed the liver hematogenously, typically with Staphylococcus or Streptococcus species 5

• Dental procedures may lead to hematogenous seeding 3

Pre-existing Liver Lesions

• Abscesses can develop within pre-existing liver pathology including biliary cysts, hydatid cysts, cystic metastases, or necrotic metastases 6

• Chronic enteric biliary contamination (from sphincterotomy or bilioenteric anastomosis) increases risk when performing interventional procedures 6

Special Populations and Associations

• Inflammatory bowel disease (IBD) patients, particularly those with Crohn's disease and transmural inflammation, have increased risk through direct extension, portal pylephlebitis, or fistulizing disease 7

• Immunocompromised patients are at risk for atypical organisms including fungi, Nocardia, and Mycobacteria 1

• Patients with diabetes mellitus have increased susceptibility to Klebsiella pneumoniae liver abscess with potential for metastatic spread 6