Peritonitis

• Peritonitis refers to inflammation of the peritoneum, which is the lining of the abdomen.
• • Parietal peritoneum: lines the abdominal cavity. Boundaries are the pelvis inferiorly, retroperitoneal space posteriorly, diaphragm superiorly, and abdominal wall anteriorly
  • Visceral peritoneum: wraps around the visceral (internal) organs located within the intraperitoneal space
  • Peritoneal cavity: a potential space located between the parietal and visceral peritoneum. It contains a small amount of fluid (~50 mL)
• Peritonitis is most commonly caused by perforation of an abdominal viscera (e.g. appendix, colon, gallbladder). It classically causes ‘peritonism’, which refers to the signs and symptoms of peritonitis that principally includes severe abdominal pain that is worse on movement and associated with percussion tenderness and rigidity
• Primary peritonitis:

  • Spontaneous bacterial invasion of the peritoneal cavity
  • Also known as spontaneous bacterial peritonitis
  • Seen in patients with pre-existing ascites (mainly chronic liver disease)
• Secondary peritonitis:

  • Perineal infection due to loss of integrity of the gastrointestinal or urogenital tracts
  • Contamination of the peritoneal space
  • Perforation causes secondary peritonitis
• Tertiary peritonitis:

  • Recurrent or persistent infection of the peritoneal cavity
  • Typically occurs after secondary peritonitis
  • Usually seen in patients who are immunocompromised
• • Localised: this refers to a focus of infection that is usually walled-off or contained by adjacent organs
  • Generalised: also known as diffuse, this refers to an infection that has spread throughout the entire cavity
• Mostly commonly caused by GI perforation:

  • Most commonly perforated appendix, diverticulum or peptic ulcer
  • Oesophagus - penetrating trauma, Boerhaave syndrome, malignancy
  • Stomach - malignancy, peptic ulcers
  • Pancreatitis
  • Hepatobiliary - gallstones, cholecystitis, malignancy
  • Small intestine - ischaemic bowel, strangulated hernias
  • Large intestines - diverticulitis, colorectal cancer
• A localised infection may develop because the infection becomes walled-off or is contained by the positioning of adjacent organs. In this situation, an abscess may develop in an attempt to control the spread of infection. 
• Abdominal pain is often dull and poorly localised initially due to inflammation of the visceral peritoneum. As the parietal peritoneum becomes involved, pain becomes more severe, sharp, and localised (e.g. acute appendicitis causing periumbilical pain that subsequently migrates to the right iliac fossa).
• Symptoms:

  • Abdominal pain - may be localised or generalised
  • Pain worse on movement
  • Abdominal distension
  • Anorexia
  • Nausea and vomiting
  • Fever
• Signs:

  • Tenderness on palpation
  • Percussion tenderness
  • Guarding
  • Rigidity
  • Fever
  • Tachycardia
  • Absent/reduced bowel sounds
  • Inflammatory mass - may suggest an abscess
  • Features of septic shock
• make sure you check the hernial orifices in a patient with suspected peritonitis to exclude a strangulated hernia.
• Blood tests:

  • Urgent
  • FBC
  • Renal profile
  • LFTs
  • VBG/ABG - lactate, metabolic acidosis
  • CRP
  • Coagulation
  • Group and save +/- crossmatch
• Imaging:

  • Usually CT with contrast
  • Erect CXR can detect air under the diaphragm but small amounts of air can be missed
• Management:

  • Broad spectrum antibiotics - usually triple therapy
  • Supportive e.g. fluids, oxygen
  • Most patients will require surgical intervention e.g. exploratory laparotomy
  • Radiological - localised peritonitis and the development of an abscess may be drained