Bacterial abscess of the liver is relatively rare; however, it has been described since the time of Hippocrates (400 BCE), with the first published review by Bright appearing in 1936. In 1938, Ochsner's classic review heralded surgical drainage as the definitive therapy; however, despite the more aggressive approach to treatment, the mortality remained at 60-80%.
The development of new radiologic techniques, the improvement in microbiologic identification, and the advancement of drainage techniques, as well as improved supportive care, have reduced mortality to 5-30%; yet, the prevalence of liver abscess has remained relatively unchanged. Untreated, this infection remains uniformly fatal.
The three major forms of liver abscess, classified by etiology, are as follows:
Pyogenic abscess, which is most often polymicrobial, accounts for 80% of hepatic abscess cases in the United States
Amebic abscess due to Entamoeba histolytica accounts for 10% of cases
Fungal abscess, most often due to Candida species, accounts for fewer than 10% of cases
Polymicrobial involvement is common, with Escherichia coli and Klebsiella pneumoniaebeing the two most frequently isolated pathogens (see the image below). Reports suggest that K pneumoniae is an increasingly prominent cause.
Enterobacteriaceae are especially prominent when the infection is of biliary origin. Abscesses involving K pneumoniae have been associated with multiple cases of endophthalmitis.
The pathogenic role of anaerobes was underappreciated until the isolation of anaerobes from 45% of cases of pyogenic liver abscess was reported in 1974. Since that time, increasing rates of anaerobic involvement have been reported, likely because of increased awareness and improved culturing techniques. The most frequently encountered anaerobes are Bacteroides species, Fusobacterium species, and microaerophilic and anaerobic streptococci. A colonic source is usually the initial source of infection.
Staphylococcus aureus abscesses usually result from hematogenous spread of organisms involved with distant infections, such as endocarditis. S milleri is neither anaerobic nor microaerophilic. It has been associated with both monomicrobial and polymicrobial abscesses in patients with Crohn disease, as well as with other patients with pyogenic liver abscess.
Amebic liver abscess is most often due to E histolytica. Liver abscess is the most common extraintestinal manifestation of this infection.
Fungal abscesses primarily are due to Candida albicans and occur in individuals with prolonged exposure to antimicrobials, hematologic malignancies, solid-organ transplants, and congenital and acquired immunodeficiency. Cases involvingAspergillus species have been reported.
Other organisms reported in the literature include Actinomyces species, Eikenella corrodens, Yersinia enterocolitica, Salmonella typhi, and Brucella melitensis.
A small case series in Taiwan investigated pyogenic liver abscess as the initial manifestation of underlying hepatocellular carcinoma. In regions with a high prevalence of both pyogenic liver abscess and hepatocellular carcinoma, clinicians should be aware of the possibility of underlying hepatocellular carcinoma in patients with risk factors for the disease.
The most frequent symptoms of hepatic abscess include the following:
Fever (either continuous or spiking)
Right upper quadrant pain
Cough or hiccoughs due to diaphragmatic irritation may be reported. Referred pain to the right shoulder may be present.
Individuals with solitary lesions usually have a more insidious course with weight loss and anemia of chronic disease. With such symptoms, malignancy often is the initial consideration.
Fever of unknown origin (FUO) frequently can be an initial diagnosis in indolent cases. Multiple abscesses usually result in more acute presentations, with symptoms and signs of systemic toxicity.
Afebrile presentations have been documented.
Fever and tender hepatomegaly are the most common signs. A palpable mass need not be present. Midepigastric tenderness, with or without a palpable mass, is suggestive of left hepatic lobe involvement.
Decreased breath sounds in the right basilar lung zones, with signs of atelectasis and effusion on examination or radiologically, may be present. A pleural or hepatic friction rub can be associated with diaphragmatic irritation or Glisson capsule inflammation.
Jaundice may be present in as many as 25% of cases and usually is associated with biliary tract disease or the presence of multiple abscesses.
Complications of liver abscess may include the following:
Empyema resulting from contiguous spread or intrapleural rupture of abscess
Rupture of abscess with resulting peritonitis
Endophthalmitis when an abscess is associated with K pneumoniae bacteremia
An untreated hepatic abscess is nearly uniformly fatal as a result of complications that include sepsis, empyema, or peritonitis from rupture into the pleural or peritoneal spaces, and retroperitoneal extension. Treatment should include drainage, either percutaneous or surgical.
Antibiotic therapy as a sole treatment modality is not routinely advocated, though it has been successful in a few reported cases. It may be the only alternative in patients too ill to undergo invasive procedures or in those with multiple abscesses not amenable to percutaneous or surgical drainage. In these instances, patients are likely to require many months of antimicrobial therapy with serial imaging and close monitoring for associated complications.
Surgical drainage was the standard of care until the introduction of percutaneous drainage techniques in the mid-1970s. With the refinement of image-guided techniques, percutaneous drainage and aspiration have become the standard of care.
Current indications for the surgical treatment of pyogenic liver abscess are for the treatment of underlying intra-abdominal processes, including signs of peritonitis; existence of a known abdominal surgical pathology (eg, diverticular abscess); failure of previous drainage attempts; and the presence of a complicated, multiloculated, thick-walled abscess with viscous pus.
Shock with multisystem organ failure is a contraindication for surgery.
Open surgery can be performed by either of the following two approaches:
A transperitoneal approach allows for abscess drainage and abdominal exploration to identify previously undetected abscesses and the location of an etiologic source
For high posterior lesions, a posterior transpleural approach can be used; although this affords easier access to the abscess, the identification of multiple lesions or a concurrent intra-abdominal pathology is lost