Intra-abdominal abscess

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Referral

Definition

An intra-abdominal abscess is a localised collection of pus within the peritoneal cavity, typically caused by infection following abdominal surgery, trauma, or gastrointestinal perforation.

Aetiology

Common causes of intra-abdominal abscess include:

  • Perforated appendicitis or diverticulitis.
  • Perforated peptic ulcer.
  • Post-surgical complications (e.g., anastomotic leak).
  • Trauma leading to organ perforation.
  • Pelvic inflammatory disease (leading to tubo-ovarian abscess).
  • Ischaemic bowel.
  • Infected pancreatic pseudocyst (in pancreatitis).

Pathophysiology

The development of an intra-abdominal abscess occurs due to:

  • Bacterial invasion of the peritoneal cavity from a perforated organ or surgical site.
  • Localised inflammation leading to pus formation, surrounded by a fibrous wall (capsule).
  • Sequestration of bacteria, necrotic tissue, and immune cells within the abscess cavity.

Risk factors

  • Recent abdominal surgery or trauma.
  • Perforated gastrointestinal conditions (e.g., appendicitis, diverticulitis).
  • Chronic illnesses (e.g., diabetes, immunosuppression).
  • Previous intra-abdominal infections.
  • Prolonged hospitalisation or ICU stay.

Signs and symptoms

Symptoms:

  • Fever and chills.
  • Abdominal pain (localised to the affected area).
  • Nausea and vomiting.
  • Malaise and fatigue.
  • Anorexia and weight loss.

Signs:

  • Tenderness on palpation of the abdomen.
  • Guarding or rebound tenderness (if peritonitis is present).
  • Abdominal distension.
  • Palpable mass (in some cases).
  • Tachycardia and hypotension (if sepsis develops).

Investigations

Key investigations to confirm diagnosis and assess severity:

  • Blood tests:
    • Raised white cell count (WCC) indicating infection.
    • Elevated CRP and ESR levels suggesting inflammation.
    • Blood cultures (if sepsis is suspected).
  • Imaging:
    • CT scan (gold standard): identifies abscess location, size, and extent.
    • Ultrasound: useful for superficial or pelvic abscesses.
    • X-ray: may show free air under the diaphragm if perforation has occurred.
  • Fluid analysis: aspirated pus for Gram stain and culture to identify causative organisms.

Management

Management of intra-abdominal abscess involves a combination of medical and surgical approaches:

1. Supportive Care:

  • Intravenous fluids (IV): to correct dehydration and maintain haemodynamic stability.
  • Analgesia: paracetamol or opiates for pain relief.

2. Antibiotic Therapy:

  • Broad-spectrum antibiotics targeting gram-negative, anaerobic, and gram-positive bacteria.
  • Tailor antibiotics based on culture results.

3. Source Control:

  • Percutaneous drainage: first-line for accessible abscesses under ultrasound or CT guidance.
  • Surgical drainage: performed for large abscesses or when percutaneous drainage is not feasible.
  • Definitive repair: to address underlying cause (e.g., repair of perforated organ or anastomotic leak).

Referral

  • Urgent referral to secondary care:
    • Severe sepsis or haemodynamic instability.
    • Signs of generalised peritonitis.
    • Large or inaccessible abscess requiring surgical drainage.
  • Specialist involvement:
    • Interventional radiology for percutaneous drainage.
    • Surgical team for operative intervention.
GastroenterologymypanotesIntra-abdominal abscess