Peritonitis

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

Definition

Peritonitis is an acute inflammatory condition of the peritoneal cavity, typically caused by infection, perforation of a hollow viscus, or non-infectious irritation (e.g., chemical peritonitis).

Aetiology

  • Primary peritonitis: spontaneous bacterial peritonitis (SBP) in patients with ascites due to liver disease.
  • Secondary peritonitis: due to perforation or inflammation of abdominal organs (e.g., perforated peptic ulcer, appendicitis, diverticulitis, bowel perforation).
  • Tertiary peritonitis: persistent or recurrent intra-abdominal infection despite treatment.
  • Chemical peritonitis: leakage of non-infectious irritants (e.g., bile, pancreatic enzymes, gastric acid).

Pathophysiology

  • Infection or chemical irritation triggers an inflammatory response.
  • Peritoneal fluid shifts lead to third-spacing, causing hypovolaemia and electrolyte imbalances.
  • Sepsis and multi-organ failure can occur if untreated.

Risk factors

  • Perforated peptic ulcer or bowel perforation.
  • Appendicitis or diverticulitis with perforation.
  • Peritoneal dialysis (increases risk of bacterial peritonitis).
  • Cirrhosis with ascites (risk of spontaneous bacterial peritonitis).
  • Abdominal trauma or recent surgery.

Signs and symptoms

Symptoms:

  • Severe, generalised abdominal pain (worsens with movement).
  • Abdominal distension.
  • Nausea and vomiting.
  • Fever and chills.

Signs:

  • Rigid, board-like abdomen (due to involuntary guarding).
  • Rebound tenderness and severe localised pain.
  • Absent bowel sounds (paralytic ileus).
  • Tachycardia and hypotension (signs of sepsis).

Investigations

  • Blood tests:
    • Raised white cell count and CRP (suggests infection).
    • Urea and electrolytes (assess dehydration and kidney function).
    • Liver function tests (if suspected spontaneous bacterial peritonitis).
    • Blood cultures (if sepsis is suspected).
  • Imaging:
    • Abdominal X-ray: free air under the diaphragm suggests perforation.
    • CT abdomen (gold standard): identifies the cause and extent of inflammation.
  • Ascitic fluid analysis (if ascites present):
    • Neutrophils raised, which suggest spontaneous bacterial peritonitis.
    • Culture and sensitivity to identify causative organisms.

Management

1. Initial Resuscitation:

  • ABCDE approach.
  • IV fluids resuscitation.
  • Broad-spectrum IV antibiotics.
  • Analgesia.

2. Specific Management Based on Cause:

  • Spontaneous bacterial peritonitis: IV abx (follow local guideline).
  • Perforated viscus (e.g., perforated ulcer, appendicitis): will likely need emergency laparotomy or laparoscopic repair.
  • Peritoneal dialysis-associated peritonitis: Intraperitoneal antibiotics (for example vancomycin).

3. Surgery and Interventional Radiology:

  • Exploratory laparotomy: if perforation, ischaemia, or bowel necrosis is suspected.
  • Abscess drainage: CT-guided percutaneous drainage if localised collections are present.

Referral

  • Emergency surgical referral: if secondary peritonitis is suspected.
  • Gastroenterology referral: for spontaneous bacterial peritonitis in liver disease.
  • A/E referral: if sepsis is suspected.
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