Hepatic Abscess

Hepatic abscess is a localised collection of pus in the liver parenchyma, most commonly pyogenic or amoebic.

• Pyogenic: biliary tract disease (stones, strictures, tumours), portal pyaemia (appendicitis, diverticulitis), haematogenous spread from endocarditis or bacteraemia, direct extension, penetrating trauma, cryptogenic (up to half); diabetes is a major risk factor. Organisms: Escherichia coli, Klebsiella pneumoniae (including invasive strains with endophthalmitis), Streptococcus anginosus group, anaerobes, Enterococcus, Staphylococcus aureus.
• Amoebic: Entamoeba histolytica, faecal-oral spread, young men, alcoholism, HIV, recent travel to or residence in endemic areas such as Kenya; usually a solitary right lobe abscess.
• Other causes: hydatid cyst, fungal abscess in neutropenia, tuberculous abscess.

Fever with chills, right upper quadrant pain, anorexia, weight loss, malaise, nausea and vomiting, jaundice (in biliary disease), right shoulder pain, cough, hiccup, tender hepatomegaly.

• Amoebic abscess develops over days to weeks; pyogenic follows an acute septic course; diarrhoea in only about 10 to 30 percent of amoebic cases.
• Differential diagnosis: cholecystitis, cholangitis, hydatid cyst, hepatocellular carcinoma, necrotic metastasis, pneumonia, empyema, subphrenic abscess, tuberculosis, Q fever.
• Complications: rupture into the peritoneum (peritonitis), pleural space (empyema), pericardium (tamponade), bile duct, colon or retroperitoneum, septicaemia, septic shock, portal vein thrombosis, hepatic vein thrombosis, endophthalmitis and metastatic infection (Klebsiella), and death.

Full blood count (leucocytosis, anaemia), C-reactive protein, liver profile (raised alkaline phosphatase, low albumin), blood cultures (positive in half of pyogenic), glucose or HbA1c.

• Ultrasound shows a hypoechoic cavity; CT with contrast shows a rim-enhancing lesion with a double target sign and gas bubbles; MRI for biliary anatomy.
• Amoebic serology (positive in over 90 percent), stool microscopy, antigen or PCR.
• Aspiration under imaging: pus (anchovy paste colour in amoebic, foul in pyogenic) with Gram stain and culture, to confirm pyogenic and exclude pyogenic superinfection.
• Chest radiograph (raised right hemidiaphragm, effusion).
• Evaluate for a source: colonoscopy for colorectal cancer in Klebsiella abscess; endocarditis echocardiography where indicated.

Supportive: intravenous fluids, analgesia, nutritional support, glycaemic control.

Pharmacological

• Pyogenic: ceftriaxone 2 g IV daily plus metronidazole 500 mg IV every 8 hours, or piperacillin-tazobactam 4.5 g IV every 6 to 8 hours (meropenem 1 g every 8 hours for severe or resistant disease), narrowed to culture; switch to oral after 2 weeks of IV therapy (amoxicillin-clavulanate 625 mg three times daily, or ciprofloxacin 500 mg twice daily with metronidazole 400 mg three times daily) for a total of 4 to 6 weeks.
• Amoebic: metronidazole 800 mg orally three times daily (or 500 mg IV every 8 hours) for 7 to 10 days, then a luminal agent to clear cysts: paromomycin 25 to 35 mg/kg/day in 3 divided doses for 7 days, or diloxanide furoate 500 mg three times daily for 10 days. Tinidazole 2 g daily for 3 days is an alternative to metronidazole.
• Children: metronidazole 10 to 15 mg/kg three times daily.

Procedures

• Percutaneous needle aspiration or catheter drainage under ultrasound or CT for pyogenic abscesses above 5 cm; repeated aspiration for smaller ones; catheter left until output falls below 10 mL daily.
• Amoebic abscess: drainage if above 5 cm, left lobe (risk of pericardial rupture), failure of drug therapy after 3 to 5 days, secondary bacterial infection, or impending rupture.
• Surgery (laparoscopic or open drainage) for rupture, multiloculated or septated abscesses, failed percutaneous drainage, or underlying biliary or colonic disease needing correction; endoscopic biliary drainage for obstruction.

Special groups: diabetes (tight glycaemic control), HIV (also treat opportunistic infection), pregnancy (metronidazole after the first trimester; drain early), neonates and children (weight based dosing).

Red flags: shock, jaundice, peritonitis, abscess more than 10 cm, rupture, no response after 72 hours.

Follow-up: repeat ultrasound at 2 weeks and 4 to 6 weeks (cavities may persist for months); clinical and inflammatory markers weekly until normal; evaluate for colorectal cancer in Klebsiella disease.