Liver Abscess

Liver abscesses are caused by bacterial, parasitic, or fungal organisms. In developed countries, pyogenic abscesses are the most common but worldwide, amoebae are the commonest cause.¹

A retrospective study over a 10 year period of patients >16 years old admitted to the Royal Hallamshire Hospital in Sheffield with a diagnosis of liver abscess found 4 patients with amoebic liver abscesses and 65 with pyogenic liver abscesses. They estimated an annual incidence for liver abscesses of 2.3 per 100,000 people per year in the UK.²

Pyogenic liver abscess

• Can be single or multiple. The right lobe is affected twice as often as the left, 5% have bilateral involvement.³
• Most secondary to infection originating in abdomen (cholangitis secondary to stones or stricture or malignancy is commonest, diverticulitis, appendicitis, crohn's disease, perforated peptic ulcer).
• May be iatrogenic secondary to liver biopsy or a blocked biliary stent.
• Bacterial endocarditis and dental infection are other causes.
• No cause found in 15%
• More common if immunocompromised
• 15% of adults with liver abscesses have diabetes.¹
• Liver cirrhosis is a strong risk factor.⁴
• Liver abscess is a complication of umbilical vein catheterisation in infants. In children and adolescents there is usually immune compromise or trauma.
• Tends to be polymicrobial. Organisms usually of bowel origin with E. coli and Klebsiella pneumoniae, Bacteroides spp., Enterococci and anaerobic Streptococci the most common. Staphylococci and haemolytic Streptococci more likely if secondary to endocarditis/dental infection. Fungal (Candida spp. most common) or opportunistic organisms more likely if patient immunocompromised.¹

Amoebic liver abscess

• 10% of the world's population is chronically infected with Entamoeba histolytica.¹ Infection occurs most commonly in tropical and subtropical areas and is more likely if there is poor sanitation and overcrowding.
• Transmission is via the faecal-oral route. Amoebae invade intestinal mucosa and can gain access to the portal venous system.
• E. histolytica causes amoebic colitis and dysentery but liver abscess is the most common extra-intestinal manifestation of infection.⁵
• Liver abscess can present without a preceding history of colitis. It can also present months to years after travel to an endemic area.
• Affects the right lobe in 80%.¹

• Multiple abscesses tend to present more acutely and single ones more indolently
• Right upper quadrant pain, tenderness, hepatomegaly, possible palpable mass
• Swinging fever
• Night sweats
• Nausea and vomiting
• Anorexia and weight loss
• Cough and dyspnoea due to diaphragmatic irritation
• Referred pain to the right shoulder
• Jaundice (in 25% of cases, commoner with disease of the biliary tree and multiple abscesses)³
• Pyogenic liver abscesses can present as pyrexia of unknown origin in some people who may not have right upper quadrant pain; pain is a prominent feature in amoebic liver abscess
• Check history for travel to an Entamoeba histolytica endemic area

• Causes of pyrexia of unknown origin (PUO)
• Metastatic malignancy affecting the liver
• Hepatocellular carcinoma
• Biliary disease including cholecystitis
• Bacterial pneumonia
• Gastritis

• Raised white cell count
• Raised ESR
• Mild normochromic normocytic anaemia
• Abnormal liver function tests (raised alkaline phosphatase, low albumin, raised serum transaminases, raised bilirubin)
• Blood culture is positive in 50%³
• Stools can contain entamoeba cysts or trophozoites
• Serology should be carried out if Entamoeba histolytica suspected
• Raised right hemidiaphragm on CXR. May be atelectasis or pleural effusion.
• Ultrasonography can show abscess and also allow guided percutaneous aspiration and drainage. Aspirated fluid should be sent for culture and sensitivity. It also allows biliary tree examination.
• CT scanning can show the abscess, allow guided aspiration and drainage and show other intra-abdominal abscesses or a possible cause such as diverticular disease, appendicitis etc. It is good for the detection of small abscesses.
• ERCP can show the site and cause of biliary obstruction and allow stenting and drainage.
• Investigation should always seek to determine the underlying cause.

Antibiotics

• Pyogenic liver abscess: broad spectrum antibiotics should be started before waiting for culture results. Use a penicillin, an aminoglycoside and metronidazole. A third generation cephalosporin can be considered in the elderly or if renal function is impaired.¹ Antibiotic therapy can be modified once culture results are available. Treatment may be needed for up to 12 weeks and should be guided by the clinical picture and radiological monitoring.
• Amoebic liver abscess: metronidazole is the treatment of choice. 95% of patients with amoebic liver abscess recover with this alone. Most patients show a response to treatment within 72-96 hours.⁶ Diloxanide furoate should be prescribed for 10 days to eliminate intestinal amoebae after the abscess has been successfully treated.
• Antifungal agents such as amphotericin B are used if fungal abscess is suspected.

Drainage

• Most patients with pyogenic liver abscess, and those will very large amoebic abscesses, may not recover with antibiotics alone and need drainage guided by ultrasonography or CT.
• Percutaneous aspiration can be carried out for small abscesses; larger abscesses may need catheter drainage which is also CT or ultrasound guided. Drainage should also be carried out if there is impending rupture.
• Open surgery may be necessary if the abscess has ruptured and there are signs of peritonitis or if there is a known abdominal pathology such as appendicitis.

Supportive measures

• Fluids
• Nutrition
• Pain relief

• Overwhelming sepsis
• Rupture of the abscess into adjacent structures (pleural, peritoneal and pericardial spaces)
• Secondary infection of amoebic liver abscesses

• Pyogenic liver abscess: early diagnosis and treatment with antibiotics improves outcome but mortality rates are still 5-30%.³ Factors that affect prognosis include presence of shock or disseminated intravascular coagulation (DIC), immunodeficiency, diabetes, associated malignancy, ineffective surgical drainage.¹
• Amoebic liver abscess: since the introduction of rapid diagnosis and effective medical treatment, mortality rates have fallen to 1-3%.^{6,7,8,9,10,11,12}

In the Hallamshire series described above, mortality rate was 12.3%.²