Inflammation of the peritoneum, typically caused by perforation of a hollow viscus or an infection

Aetiology

• Perforation of a hollow viscus: this can be from a perforated oesophagus (Boerhaave syndrome), a perforated duodenal or gastric ulcer, a perforated intestine (secondary to conditions such as appendicitis, diverticulitis, intestinal infarction, colorectal cancer, or inflammatory bowel disease)
• Perforation may also occur due to trauma, such as the ingestion of a foreign body
• Perforation can lead to diffuse or faeculent peritonitis
• Infection: infections leading to peritonitis include spontaneous bacterial peritonitis and peritoneal infection secondary to peritoneal dialysis
• Uncomplicated appendicities can cause local peritonitis due to inflammation of the surrounding peritoneum

Clinical features

• Severe abdominal pain - patients will often be lying completely still so as to not trigger/exacerbate pain
• Systemic signs of illness such as fever, haemodynamic instability, tachycardia
• Nausea and vomiting
• Abdominal rigidity/Involuntary abdominal guarding: involuntary tensing of the abdominal wall muscles in response to pressure on the abdomen (to protect inflamed abdominal organs)
• Rebound tenderness: pressing on the abdomen elicits less pain than releasing the hand (as the peritoneum bounces back into place)
• Percussion tenderness

Investigations

• Patients presenting with peritonitis can be very systemically unwell and the SEPSIS 6 should be initiated in these situation
• Laboratory tests: blood tests to assess for elevated white blood cell count and markers of inflammation (e.g. C-reactive protein), kidney function, and liver function
• Imaging: abdominal x-ray, ultrasound, or CT scan to identify fluid collections or perforations (looking for free gas - pneumoperitoneum, rigler’s sign and football sign)
• Peritoneal fluid analysis: if feasible, an analysis of peritoneal fluid obtained by paracentesis can help identify the causative organism and guide treatment

Management