B37. Peritonitis: Causes, therapy, complications

Peritonitis is the inflammation of the peritoneum, which lines the abdominal wall and most abdominal organs. We distinguish primary peritonitis (spontaneous bacterial peritonitis, discussed separately) and secondary peritonitis, usually called just "peritonitis".

Secondary peritonitis is peritonitis caused by bacterial infection from a surgically treatable intraabdominal source, like GI perforation, appendicitis, trauma, etc.

Secondary peritonitis is usually a polymicrobial infection. It may be generalised or local (affecting only part of the abdomen). Peritonitis secondary to bowel perforation is usually called faecal peritonitis.

Peritonitis is a severe condition as it has a high risk of progressing to sepsis with high mortality. The underlying cause must be sought and treated.

Etiology

Generalised peritonitis occurs due to:

• Perforation of an abdominal organ
  • Perforated duodenal ulcer
  • Perforated appendicitis
  • Perforated diverticulitis
  • Mesenteric ischaemia
  • Surgical complication
• Leakage of intestinal anastomosis
• Penetrating wounds to the abdomen

Localised peritonitis occurs due to:

• Abdominal organ inflammation with spread to adjacent peritoneum
  • Appendicitis
  • Diverticulitis
  • Pancreatitis

Clinical features

Peritonitis causes peritonitic abdominal pain. Movement usually worsens the pain, causing the patient to lie completely still, usually with the knees bent. Even gentle percussion over the affected area of the abdomen causes pain. “Guarding” on palpation, as well as rebound tenderness, are typical signs of peritonitis. The heel-drop test may be positive.

If generalised, peritonitis also causes signs of infection like fever.

Peritonitic signs in only one quadrant means local peritonitis is probable, while peritonitic signs affecting the abdomen diffusely is suspicious for generalised peritonitis.

Diagnosis and evaluation

The presence of peritonitis is usually established by physical examination, but the underlying cause must be sought. Stable patients should undergo imaging (x-ray, CT, ultrasonography) to identify the underlying cause. However, unstable or very ill-appearing patients may skip imaging to avoid delaying surgery.

Treatment

The treatment of generalised peritonitis involves supportive therapy, empiric wide-spectrum antibiotics, and treatment of the underlying cause, which almost always requires surgery. Local peritonitis does not invariably require antibiotics, for example when caused by appendicitis.