Amoebic Liver Abscess Requiring Drainage

Amoebic liver abscess is an extraintestinal manifestation of Entamoeba histolytica infection caused by portal spread from the colon.

Most abscesses are solitary and located in the right hepatic lobe.

Unlike pyogenic liver abscess, most uncomplicated amoebic abscesses respond rapidly to nitroimidazole therapy and do not require routine drainage.

Drainage becomes important when rupture risk, left lobe location, diagnostic uncertainty or failure of medical treatment makes drug therapy alone unsafe.

Typical presentation is fever with right upper quadrant pain and hepatic tenderness.

Patients may have weight loss, malaise and anorexia.

Concurrent diarrhoea is absent in many patients, so lack of intestinal symptoms does not exclude amoebiasis.

Jaundice is uncommon in uncomplicated disease and should increase concern for a large abscess, biliary compression, multiple lesions or another diagnosis.

A left lobe abscess is particularly dangerous because rupture can involve the pericardium.

Ultrasound: confirms the hepatic abscess and determines its size, position and proximity to the capsule.

Serology is strongly supportive in an appropriate epidemiological setting.

Stool microscopy has limited sensitivity and may be negative because hepatic disease can occur without active intestinal symptoms.

If the diagnosis remains uncertain, aspirated material should undergo appropriate microbiological assessment to distinguish amoebic from pyogenic infection.

Antiamoebic treatment

First line treatment is:

Metronidazole 750 mg orally or IV three times daily for 7 to 10 days.

Most patients show substantial symptomatic improvement within approximately 48 to 72 hours.

Metronidazole eradicates invasive trophozoites but does not reliably eliminate intraluminal colonic cysts.

After metronidazole, give a luminal amoebicide:

Paromomycin 500 mg orally three times daily for 7 days

or approximately 25 to 35 mg/kg/day orally in three divided doses for 7 days.

Luminal treatment is required even when stool examination is negative.

Drainage

Do not aspirate every amoebic liver abscess.

Image guided needle aspiration or catheter drainage should be considered when there is:

• No meaningful clinical improvement after 48 to 72 hours of appropriate metronidazole
• Large abscess, particularly above approximately 5 to 10 cm
• Left lobe abscess
• Very thin residual rim of liver tissue, approximately below 10 mm
• Impending rupture
• Severe persistent pain from capsular tension
• Diagnostic uncertainty between amoebic and pyogenic abscess
• Secondary bacterial infection.

Needle aspiration is sufficient for many liquefied uncomplicated abscesses requiring decompression.

Use catheter drainage when the cavity is very large, rapidly reaccumulates or requires continuing evacuation.

Surgery

Open or laparoscopic drainage is rarely required.

Operate for:

• Free intraperitoneal rupture with peritonitis
• Rupture into another compartment not controlled percutaneously
• Failed percutaneous drainage
• Major diagnostic uncertainty requiring operative intervention
• Another simultaneous surgical pathology

Continue antiamoebic treatment even after successful drainage because aspiration alone does not eradicate E. histolytica infection.