Liver Abscess

I. What every physician needs to know.

Liver abscesses can be broadly categorized by causative factor into those that are amebic or pyogenic, with important diagnostic and treatment implications for each. Pyogenic abscesses are most common and occur either by local spread from intraabdominal infection or by hematogenous spread, typically from Klebsiella lung infection.

Most pyogenic abscesses are caused by polymicrobial enteric flora in the setting of hepatobiliary disease or intraabdominal infection and often present with fever, abdominal pain, nausea, and malaise. By contrast, Klebsiella pneumoniae primary liver abscesses are monomicrobial and occur without associated hepatobiliary disease. These are thought to develop by hematogenous spread from a primary lung infection and are found most commonly in patients with diabetes.

Amebic liver abscess is a consequence of ingestion of Entamoeba histolytica present in fecal contamination of food, typically in developing countries. These protozoan parasites migrate to the liver via the portal vein.

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II. Diagnostic Confirmation: Are you sure your patient has Liver Abscess?

A. History Part I: Pattern Recognition:

The diagnosis of liver abscess requires a high index of suspicion because most symptoms are non-specific. These include fever, abdominal pain, fatigue, and nausea with fever being the most common symptom present in up to 90% of cases of pyogenic abscesses.

Patients with pyogenic liver abscesses tend to be more jaundiced and potentially septic as compared to those with amebic liver abscesses.

Rarely, patients with Klebsiella liver abscesses (KLA) may also have evidence of metastatic infection such as endophthalmitis, meningitis, brain abscess, and septic emboli to other organs. Clinical manifestations associated with distant organ dysfunction in the setting of Klebsiella pneumoniae bacteremia should prompt evaluation of liver function.

Amebic liver abscesses usually present acutely with 1-2 weeks of fever and right upper quadrant abdominal pain; however, more subacute to chronic presentations manifesting with fatigue, low grade fever, and weight loss have been described in some patients returning from endemic areas. Antecedent diarrhea is described in only about 30% of patients.

B. History Part 2: Prevalence:

Liver abscesses are the most common visceral abscess with an annual incidence around 2.3 cases per 100,000 persons.

Polymicrobial liver abscesses are seen in patients with peritonitis after intraabdominal viscus rupture or by direct spread from biliary infection, with up to half of cases having underlying biliary tract disease. Risk factors include diabetes, hepatobiliary and pancreatic disease, and prior liver transplantation.

Klebsiella liver abscesses are most prevalent in Asian populations and often occur in the setting of poorly-controlled diabetes.

Amebic liver abscess should be considered in recent travelers to endemic areas, which include India, Africa, Mexico, and Central and South America. Despite equal prevalence of colonic amebiasis, amebic liver abscesses are 7-10 times more common in adult men, most frequently in the fourth and fifth decades.

C. History Part 3: Competing diagnoses that can mimic Liver Abscess.

Pyogenic liver abscesses need to be distinguished from hepatic cysts and tumors. History and physical exam will give clues to the diagnosis since pyogenic liver abscesses present acutely or subacutely and are associated with systemic complaints such fever and abdominal pain. Metastatic disease to the liver is frequently discovered by imaging which then leads to further imaging tests while searching for a primary.

Hydatid cysts of the liver caused by ingestion of the larval form of the tapeworm Echinococcus granulosis are rare in the United States. Patients with hydatid cysts usually present with hepatomegaly as opposed to pain or fever; however, hydatid cysts, particularly when large, may rupture into the biliary tree leading to cholangitis and pancreatitis.

D. Physical Examination Findings.

Signs of liver abscess are non-specific, but most patients are febrile on presentation. Severe disease can present with more systemic involvement, including severe sepsis. Approximately half of patients have right upper quadrant tenderness, hepatomegaly, or jaundice.

E. What diagnostic tests should be performed?

1. What laboratory studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

Initial lab work-up should include a complete blood count (CBC), liver function tests (LFT’s), and blood cultures. Leukocytosis is often seen on CBC. Patients with a pyogenic abscess typically have an elevated alkaline phosphatase, with elevation in bilirubin and aspartate aminotransferase seen less commonly. Patients with an amebic liver abscess tend to have a normal alkaline phosphatase. Blood cultures should be drawn because they are positive in over half of patients.

Once a liver abscess is confirmed radiologically, fluid should be aspirated and tested by gram stain as well as aerobic and anaerobic cultures.

Stool cultures should be obtained if Entamoeba histolytica is suspected; however, amebae are only identified in about 18% of patients. Serum antibodies should also be obtained and are detectable in 92-97% of patients on admission (although antibodies persist for many years and preclude diagnosis of acute infection in patients residing in high prevalence areas). Aspiration of amebic liver abscess is usually not performed unless there is concern for imminent rupture or inadequate response to therapy. If aspiration is performed, aspirated material consists of necrotic hepatocytes and is described as having “anchovy paste” appearance. Entamoeba species are rarely identified from the aspirate. This is in contrast to a more common polymicrobial liver abscess aspirate, which usually contains organisms easily identified on gram stain.

Serological testing with ELISA is used when presence of Echinococcal cyst is considered.

2. What imaging studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

Right upper quadrant ultrasound and abdominal computerized tomography (CT) are the preferred imaging modalities. Abdominal CT typically shows a fluid collection with surrounding edema. Elevated right hemidiaphragm may also be seen. Klebsiella pneumoniae liver abscesses tend to be more solid-appearing and are usually solitary.

By comparison, tumors typically have a solid appearance and may be calcified. Cysts are described as well-demarcated, fluid-filled structures without surrounding edema and do not enhance with contrast. Metastasis from adenocarcinoma are usually multiple.

Echinococcal cysts are commonly smooth, round, and virtually indistinguishable from benign cysts.

F. Over-utilized or “wasted” diagnostic tests associated with this diagnosis.

Abdominal X-ray has poor utility for evaluating for a liver abscess. Magnetic resonance imaging (MRI) and tagged white blood cell scans are usually not needed to diagnose liver abscess.

III. Default Management.

  • Draw peripheral blood cultures

  • Check complete blood count, basic metabolic panel, and liver function tests

  • RUQ ultrasound or abdominal CT

  • Percutaneous radiologically-guided aspiration

  • Empiric antibiotics

A. Immediate management.

Most pyogenic liver abscesses should be aspirated by ultrasound-guided or CT-guided percutaneous drainage, often with placement of catheter to allow additional drainage. Needle aspiration (with or without catheter placement) is performed for an abscess <5cm in diameter, and catheter drainage is used for larger abscesses. Repeat needle aspiration may be required in up to half of abscesses <5cm if a catheter is not left in place. Drains typically remain in place for up to 7 days or until drainage is minimal. Of note, Klebsiella liver abscess aspiration frequently yields relatively small amount of pus as compared to other causative agents.

Surgical drainage is generally recommended when there are multiple abscesses, loculated abscesses, inadequate response to percutaneous drainage after 7 days, or underlying disease that requires surgical management.

Broad spectrum antibiotics that cover enteric flora should be started without delay while gram stain and cultures are pending. Ampicillin-sulbactam, piperacillin/tazobactam, ticarcillin-clavulanate, or ceftriaxone plus metronidazole are all acceptable first choice options; though carbapenem monotherapy or a combination of metronidazole and a fluoroquinolone may also be used. Once culture and sensitivities are reported antibiotic choice may be narrowed; however, high incidence of polymicrobial infections must be kept in mind.

For amebic liver abscesses, oral metronidazole administered for 7-10 days leads to a cure rate of over 90%. Intraluminal therapy with paromomycin, diiodohydroxyquin, or diloxanide furoate is required after successful treatment with oral metronidazole because parasites persist in 40-60% of patients treated with metronidazole alone.

Bacterial coinfection of amebic liver abscess has been observed. When this is suspected broad spectrum antibiotics as described above should be added.

Echinococcal cysts are generally not aspirated due to potential of causing spread of the disease or overwhelming sepsis and are instead managed primarily by either surgical or laparoscopic techniques.

B. Physical Examination Tips to Guide Management.

Systemic symptoms such as fever and abdominal pain should abate with treatment.

C. Laboratory Tests to Monitor Response To, and Adjustments in, Management.

Radiological abnormalities resolve slower than clinical improvement, thus follow up imaging is rarely performed but should be considered if there is no clinical improvement or catheter drainage is insufficient.

Leukocytosis generally resolves with treatment.

D. Long-term management.

Patients with pyogenic abscesses are usually treated with 4 to 6 weeks of total antibiotics depending on clinical improvement, initial presence and type of bacteremia and complete versus partial catheter drainage of the abscess. Patients with a good initial response and adequate drainage are often treated with 2 to 4 weeks of parenteral antibiotics and then complete the remainder of the course with oral therapy tailored to culture results. Those with incomplete drainage are treated with 4 to 6 weeks of parenteral therapy.

Intraluminal treatment with paromomycin, diiodohydroxyquin, or diloxanide furoate should follow successful metronidazole treatment of amebic liver abscess.

E. Common Pitfalls and Side-Effects of Management.

IV. Management with Co-Morbidities.

A. Renal Insufficiency.

No change in standard management.

B. Liver Insufficiency.

No change in standard management.

C. Systolic and Diastolic Heart Failure.

No change in standard management.

D. Coronary Artery Disease or Peripheral Vascular Disease.

No change in standard management.

E. Diabetes or other Endocrine issues.

No change in standard management.

F. Malignancy.

In patients with hepatocellular carcinoma who are treated with transarterial embolization, Staphylococcal species are frequently isolated.

G. Immunosuppression (HIV, chronic steroids, etc).

Candidal liver abscess are found in patients with underlying malignancy who are undergoing chemotherapy and are part of the reconstitution syndrome.

H. Primary Lung Disease (COPD, Asthma, ILD).

No change in standard management.

I. Gastrointestinal or Nutrition Issues.

No change in standard management.

J. Hematologic or Coagulation Issues.

No change in standard management.

K. Dementia or Psychiatric Illness/Treatment.

No change in standard management.

V. Transitions of Care.

A. Sign-out considerations While Hospitalized.


B. Anticipated Length of Stay.

Length of stay is determined by clinical response, presence or absence of bacteremia, and presence of co-morbidities such as an underlying malignancy.

C. When is the Patient Ready for Discharge.

Prior to discharge, patients should have resolution of systemic symptoms such as fever and leukocytosis. Additionally, catheter drainage should be either complete or unabated, and a PICC line should be in place for continuous antibiotic therapy.

D. Arranging for Clinic Follow-up.

1. When should clinic follow up be arranged and with whom.

Most patients will need to follow up with an infectious disease clinic and potentially interventional radiology for catheter removal / follow up.

2. What tests should be conducted prior to discharge to enable best clinic first visit.


3. What tests should be ordered as an outpatient prior to, or on the day of, the clinic visit.

Depending on the antibiotics used, complete blood count, basic metabolic panel, and liver function tests may need to be obtained and followed as outpatient.

E. Placement Considerations.

Many patients remain on parenteral antibiotics at the time of discharge and therefore require home health to administer antibiotics and monitor their PICC line. Some patients may require a temporary stay at an inpatient rehabilitation facility upon discharge.

F. Prognosis and Patient Counseling.

Mortality rates range from 2 to 12% for pyogenic liver abscesses in developed countries. Open surgical drainage, malignancy, and anaerobic infection are independent risk factors for mortality.

Mortality rates are <1% for uncomplicated amebic liver abscess with prompt diagnosis and treatment. Hyperbilirubinemia, hypoalbuminemia, large abscess, multiple abscesses, and encephalopathy have been identified as independent risk factors for mortality.

VI. Patient Safety and Quality Measures.

A. Core Indicator Standards and Documentation.


B. Appropriate Prophylaxis and Other Measures to Prevent Readmission.


VII. What's the evidence?


**The original source for this chapter was Dr Mark Krivopal. The chapter was revised for this program by Dr Winter Williams.

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