Pyogenic Liver Abscess — Surgical Notes

Source note: SRB's Manual of Surgery is not available in this library. These notes are compiled from Sabiston Textbook of Surgery (12th ed.), Mulholland & Greenfield's Surgery (7th ed.), and Sleisenger & Fordtran's GI & Liver Disease — all equally authoritative surgical references.

Definition

Epidemiology

• Annual incidence: ~2.3 cases per 100,000 persons
• Most common type of visceral abscess (13% of intra-abdominal abscesses)
• Historically affected young adults (20s–30s) due to appendicitis; now predominantly affects patients in their 50s–60s
• Male-to-female ratio: ~1.5:1 (no significant ethnic/geographic difference)
• Right lobe affected in ~75% of cases (due to greater portal venous flow)

Aetiology & Routes of Infection

Historical note: Ochsner and DeBakey (1938) described 47 cases — appendicitis via portal vein was then the dominant cause. Today, biliary disease and cryptogenic causes predominate in Western countries. In Asia, recurrent pyogenic cholangitis (intrahepatic stones) remains important.

Risk Factors

• Diabetes mellitus (most important comorbidity)
• Cirrhosis
• Chronic renal failure
• Malignancy / immunosuppression (AIDS, haematologic malignancy → fungal abscesses)
• Liver transplantation
• Previous hepatobiliary/pancreatic disease or surgery
• Chronic granulomatous disease (children — susceptibility to S. aureus)
• Atrophic gastritis / loss of gastric acid (altered bowel flora in elderly)
• Colorectal cancer: population studies from Taiwan showed a fourfold increased incidence of GI malignancy in PLA patients — especially with Klebsiella pneumoniae

Microbiology

• Escherichia coli — most frequently isolated
• Klebsiella pneumoniae — especially virulent strains cause liver abscess without underlying hepatobiliary disease, often with metastatic septic complications
• Enterobacter, Pseudomonas, Proteus, Citrobacter spp.

• Streptococcus milleri (anginosus) group — important
• Enterococcus, S. aureus (especially in children and septicaemia), S. pyogenes

• Bacteroides fragilis — most common anaerobe
• Fusobacterium necrophorum
• Anaerobic streptococci, Peptostreptococcus, Prevotella

• Salmonella Typhi — PLA complicating recurrent pyogenic cholangitis
• Candida — in immunocompromised hosts (haematologic malignancy)
• Mycobacterium tuberculosis — rare
• Actinomyces, Clostridium — uncommon

Pathology

• Right lobe involved in ~75% of cases
• Multiple abscesses → suggest biliary source
• Single, large abscess → more often cryptogenic or portal/arterial seeding
• Gross: cavity of pus surrounded by zone of hepatic necrosis and inflammatory infiltrate
• The abscess wall eventually develops a fibrous capsule

Clinical Features

Symptoms

• Fever with chills/rigors — most common (up to 90%), may be spiking
• Right upper quadrant pain — dull, constant; increased with movement
• Anorexia, nausea, malaise, weight loss
• Pain referred to right shoulder or cough if abscess near the dome of liver (diaphragmatic irritation)
• Presentation is often insidious (subacute) — symptoms may be present for >1 month before diagnosis
• Multiple abscesses → more acute presentation, often with sepsis/shock

Signs

• Hepatomegaly with tenderness (accentuated by movement/percussion)
• Fever
• Jaundice — late feature (absent early unless biliary disease is underlying cause)
• Splenomegaly — unusual, only with chronic abscess
• Portal hypertension — may follow recovery if portal vein was thrombosed

Investigations

Blood Tests

None of these tests are specific — they raise suspicion that leads to imaging.

Cultures

• Blood cultures — positive in 50% of cases; should be drawn before starting antibiotics
• Aspirate cultures — aerobic + anaerobic; yield ~90% (lower if antibiotics already started)
• Serologic testing for Entamoeba histolytica (ELISA) — in patients with epidemiologic risk factors, to exclude amebic abscess

Imaging

• Elevated right hemidiaphragm
• Right pleural effusion
• Right basal atelectasis

• Air-fluid levels in abscess cavity
• Portal venous gas (grave sign)

• Sensitivity: 80–95%
• Shows hypoechoic, round/oval lesion; distinguishes solid from cystic
• Can guide needle aspiration
• Limitation: poor visualisation of high dome lesions; operator-dependent

• Sensitivity: 95–100%
• Hypodense lesion with rim enhancement (in <20%)
• Detects small abscesses, multiple lesions, gas in cavity
• Gas in abscess = associated with increased mortality
• Identifies underlying cause (biliary stones, diverticulitis, appendicitis, malignancy)

• More sensitive than CT for small abscesses
• Low signal on T1, high signal on T2, gadolinium enhancement
• No clear advantage over CT for diagnosis; better for biliary tree assessment

Differential Diagnosis

Pyogenic vs. Amebic Liver Abscess — Key Comparison

Treatment

1. Antibiotics

• Start broad-spectrum IV antibiotics immediately once diagnosis suspected (do not wait for cultures)
• Coverage must include: streptococci, enteric gram-negative bacilli, and anaerobes
• Standard empiric regimens:
  • Ampicillin + aminoglycoside + metronidazole (classic triple therapy)
  • 3rd-generation cephalosporin (e.g., ceftriaxone) + metronidazole (preferred in renal impairment)
  • Piperacillin-tazobactam (covers gram-negative + anaerobes)
• Narrow therapy once culture and sensitivity results available
• Duration: 14 days IV → oral for a total of 4–6 weeks
• Antibiotics alone (without drainage) → prohibitively high mortality (59–100%) in most series

2. Percutaneous Drainage (Treatment of Choice)

• Percutaneous catheter drainage (PCD) under US or CT guidance — now the standard of care
• Success rate: 66–90%
• Catheter left in place until output is minimal (~7 days)
• Aspirate sent for Gram stain, aerobic/anaerobic culture
• Advantages: avoids laparotomy, can be done at time of radiologic diagnosis, suitable for high-risk surgical patients
• Relative contraindications: ascites, coagulopathy, proximity to vital structures

• Success rate: 60–90%; often requires multiple aspirations (>1 in majority; 3+ in 25%)
• A single aspiration is a reasonable first attempt, especially for small/simple abscesses
• One RCT: catheter drainage (100% success) > aspiration alone (60% success)

3. Surgical Drainage

• Failure of percutaneous drainage
• Need for surgery to treat the primary source (e.g., appendicitis, perforated diverticulum)
• Ruptured abscess with peritonitis
• Multiple abscesses not amenable to percutaneous drainage
• Thick-walled abscess (poor catheter drainage)

• Large abscesses (>5 cm): retrospective data favour surgical drainage, but PCD still succeeds in two-thirds

4. ERCP

• Indicated when the underlying cause is biliary obstruction (stones, strictures, malignancy)
• ERCP with stenting/sphincterotomy addresses the primary biliary source

5. Treatment of Underlying Cause

• Essential for cure and prevention of recurrence
• Treat biliary disease, GI malignancy, diverticulitis, appendicitis as appropriate

Complications

• Rupture — into peritoneal cavity (peritonitis), pleural cavity (empyema), pericardium (purulent pericarditis)
• Septicaemia/septic shock
• Portal vein thrombosis → portal hypertension
• Right pleural effusion / empyema thoracis
• Subphrenic abscess
• Biliary fistula
• Hepatic failure (in massive or multiple abscesses)
• Metastatic septic emboli (K. pneumoniae virulent strains — endophthalmitis, meningitis)

Prognosis

• Mortality in Ochsner & DeBakey's era: ~70–80%
• Modern mortality: 5–30% with aggressive antibiotic therapy and drainage
• Worse prognosis with:
  • Jaundice
  • Hypoalbuminaemia
  • Multiple abscesses
  • Underlying malignancy
  • Gas in abscess cavity
  • Delay in diagnosis

Key Points (SRB-style Summary)

1. Most common visceral abscess; right lobe predominance (75%)
2. Biliary disease is now the most common identifiable cause; cryptogenic predominates overall (40%)
3. Most common organisms: E. coli and K. pneumoniae
4. Polymicrobial in majority
5. Classic triad: fever + RUQ pain + tender hepatomegaly (Charcot's triad of cholangitis if biliary origin)
6. CT (contrast-enhanced) is the investigation of choice (sensitivity 95–100%)
7. Blood cultures positive in ~50% — draw before antibiotics
8. Percutaneous catheter drainage + IV antibiotics = treatment of choice
9. Surgery reserved for failed PCD or concurrent surgical pathology
10. K. pneumoniae PLA — screen for colorectal malignancy (fourfold risk)
11. Differentiate from amebic abscess (young male, single, right lobe, anchovy sauce pus, positive serology, responds to metronidazole alone)