Pathology of Peritonitis
Peritonitis is the inflammation of the peritoneum, the thin layer of tissue that lines the inner wall of
the abdomen and covers most of the abdominal organs.
1. Etiology:
o Infectious causes:
▪ Bacterial: The most common cause, which can occur due to:
▪ Perforation of abdominal organs (e.g., appendix, stomach, intestines)
allowing bacteria to enter the peritoneal cavity.
▪ Post-surgical or post-trauma infections or after peritoneal dialysis.
▪ Fungal: Seen in immunocompromised patients.
▪ Tuberculosis: A rarer cause, typically in endemic areas.
o Non-infectious causes:
▪ Chemical peritonitis can result from bile, blood, gastric acid, or pancreatic
enzymes leaking into the peritoneal cavity.
▪ Autoimmune diseases like systemic lupus erythematosus (SLE).
▪ Tumor rupture.
2. Pathophysiology:
o Once the peritoneum is breached by infection, trauma, or chemical irritants, an
inflammatory response is triggered.
o Acute inflammation:
▪ Release of inflammatory cytokines, such as IL-1, IL-6, and TNF-α, leads to
increased vascular permeability.
▪ This results in exudation of fluid into the peritoneal cavity, leading to ascites.
▪ Leukocytes, especially neutrophils, migrate into the peritoneum to combat
infection.
o Systemic response:
▪ The local infection can spread into the bloodstream (sepsis), potentially
causing shock and multi-organ failure.
3. Clinical Features:
o Acute peritonitis: Symptoms typically include severe abdominal pain, tenderness, and
distension.
o Signs of sepsis: Fever, tachycardia, hypotension, and altered mental status.
o Guarding and rebound tenderness: In response to the inflamed peritoneum, muscles
of the abdominal wall become rigid.
Pathology of Peritonitis
4. Types of Peritonitis:
o Primary (spontaneous) bacterial peritonitis (SBP): Occurs without an obvious source
of infection, often seen in patients with liver cirrhosis and ascites.
o Secondary peritonitis: Arises from a breach in the abdominal organs, such as a
perforated ulcer, ruptured appendix, or bowel ischemia.
o Tertiary peritonitis: A more chronic and less common form that occurs after the initial
infectious cause has been treated, often in critically ill patients.
5. Complications:
o Sepsis and septic shock: A life-threatening consequence of uncontrolled infection.
o Abscess formation: Localized pockets of infection can form within the peritoneal
cavity.
o Adhesions: Fibrin deposits can lead to adhesions between organs, potentially causing
bowel obstruction.
6. Treatment:
o Antibiotics: Targeting the causative bacteria, particularly for secondary peritonitis.
o Surgical intervention: Required in cases of bowel perforation, abscess drainage, or
other structural causes.
o Supportive care: Fluid resuscitation, management of shock, and correction of
electrolyte imbalances.
Peritonitis is a medical emergency that requires prompt diagnosis and treatment to prevent life-
threatening complications like sepsis and organ failure.
