Liver Abscess

A liver abscess is a pus-filled cavity within the liver, usually caused by a biliary tract source; occasionally, multiple cavities are seen. Origin may be pyogenic, amebic, or (rarely, and usually in severely immunocompromised patients) fungal. Clinical presentation is with fever and abdominal pain but is frequently nonspecific, without localized right upper quadrant symptoms. Computed tomography (CT), both with and without intravenous and oral contrast, and ultrasound are the imaging studies of choice.

Description

The most common source of liver abscess is the biliary tree in patients with cholecystitis, choledocholithiasis, or cholangitis. Less common sources include other intra-abdominal processes, such as appendicitis or diverticulitis, and hematogenous spread from sources such as an infected heart valve or the oral cavity. Amebic liver abscess should be considered in endemic areas or patients who have been to the tropics. Fungal microabscesses are seen primarily in patients with compromised immune systems. Rarely, liver abscess may be due to trauma, secondary infection from an amebic abscess or a necrotic malignant hepatic tumor, or direct extension from local structures. Common pathogens include Streptococcus spp., Escherichia coli, Klebsiella, and Bacteroides spp. Polymicrobial infections occur in 15% to 20% of patients; approximately the same percentage have multiple abscesses. Amebic liver abscess follows vascular spread of Entamoeba histolytica from the colon in patients with the intestinal infection amebiasis. Amebic abscesses may be very large; they contain aspirate with ‘anchovy-sauce’ color and consistency. Liver abscess in a child suggests immunocompromised. A single abscess is the most common presentation; spread to the liver via the vascular route is associated with multiple abscesses. The right hepatic lobe is affected more than twice as frequently as the left, due to vascular anatomy. Aspiration of abscess fluid and subsequent culture guide antibiotic choice. Failure to culture pathogenic organism(s) may be due to prior antibiotic treatment or inadequate anaerobic culture.

Causes

  • Biliary tract infection (30%-60%): secondary to biliary obstructive and inflammatory conditions (eg, cholecystitis, choledocholithiasis, and cholangitis, especially in patients with biliary tract malignancies with biliary stents)
  • Infection from gastrointestinal or pelvic organs drained via the portal circulation (24%): examples include appendicitis, diverticulitis, and perforated bowel
  • Unknown (20%)
  • Hematogenous spread secondary to bacteremia (15%): infective endocarditis, pyelonephritis, untreated oral infections, any cause of immunocompromise in children (eg, leukemia)

Pathogens causing infection:

  • Most common bacterial causes: Escherichia coli, Klebsiella spp., Proteus, Enterococcus, Staphylococcus aureus, and Streptococcus faecalis. Streptococcus milleri and anaerobes such as Bacteroides spp. are increasingly common
  • Consider Entamoeba histolytica if the patient has recently traveled to the tropics or is from an endemic area or HIV-positive
  • Candida albicans is the likely pathogen in patients with compromised immune systems
  • Amebic liver abscess is significantly more common in men than women

Rare causes:

  • Secondary infection from amebic liver abscess, primary and secondary malignant hepatic tumors
  • Direct spread of infection from local organs (empyema of the gallbladder, perinephric abscess)
  • Fistula between the liver and infected intra-abdominal organs, such as the hepatic flexure of the colon
  • Penetrating or blunt trauma to the liver
  • Fungal pathogens in patients with compromised immune systems
  • Contributory or predisposing factors
  • Inflammatory bowel disease, particularly Crohn disease, due to loss of integrity of the mucosal barrier
  • Liver cirrhosis
  • Hepatic transplant
  • Hepatic artery embolization (usually in patients with a symptomatic but unresectable hepatocellular carcinoma)
  • Older age (particularly associated with biliary sepsis)
  • Malnutrition, malignancy, pregnancy, steroid use, and excessive alcohol intake predispose to liver abscess formation

Associated disorders

Infectious and inflammatory disorders:

  • Abscesses caused by Streptococcus milleri may be seen in patients with Crohn disease
  • Candidiasis: Candida albicans infection of the liver may occur in patients with compromised immune systems
  • Tuberculosis
  • Pyrexia of unknown origin
  • Abscesses caused by Klebsiella spp. may be associated with endophthalmitis
  • Abscesses caused by Staphylococcus aureus may be associated with infective endocarditis and other distant sources of infection
  • Empyema, peritonitis, and sepsis secondary to abscess rupture
  • Hemorrhoidal abscess
  • Pleural effusion
  • Liver cirrhosis
  • Peptic ulcer
  • Hepatitis
  • Malaria
  • Metabolic disorders:
  • Alcoholism
  • Diabetes (type 1 or type 2)

Immune deficiencies:

  • Neutrophil deficiencies (leukemia, chronic granulomatous disease)
  • Severe immunocompromise in children
  • Any cause of significant immunocompromise, for example, HIV/AIDS

Preventive measures

  • Minimize alcohol intake to maintain hepatic cellular integrity and ability to fight infection
  • Prevention of amebic abscess requires interruption of fecal-oral spread, usually through elimination of contaminated food and water. Vegetables should be washed with detergent, then soaked in vinegar to eradicate amebic cysts; water should always be boiled
  • Modification of sexual practices among men who have sex with men helps prevent infection
  • Personal hygiene practices should be supervised among institutionalized individuals to ensure adequate care
  • Improved sewage and waste disposal and water purification help eradicate amebic cysts

Treatment

Treatment involves antimicrobial therapy with or without percutaneous or surgical drainage depending on the size, number, and complexity of the abscess(es). Liver abscess is almost uniformly fatal if left untreated. Timely treatment reduces mortality to 5% to 30%