Definition Peritonitis: Inflammation of the peritoneum, the thin tissue that lines the inner wall of the abdomen and covers most of the abdominal organs. Etiology Most commonly due to a bacterial infection often secondary to abdominal trauma, surgeries, or a ruptured organ. Other causes: chemical irritants (e.g., bile, gastric acid), blood, fungi, or viruses. Types: Primary: Often due to cirrhosis or ascites, not caused by any identifiable intra-abdominal source. Secondary: Resulting from a pathological condition within the abdomen like appendicitis or diverticulitis. Tertiary: Persistent infection after treatment of primary or secondary peritonitis. Clinical Presentation Severe abdominal pain that is worsened with movement. Abdominal tenderness and rigidity (“board-like abdomen”). Fever and chills. Nausea and vomiting. Anorexia. Possible altered bowel habits. Investigations Abdominal X-ray: May show gas patterns suggestive of ileus or free air if there’s a perforation. Abdominal CT scan: Useful to determine the cause, especially in secondary peritonitis. Paracentesis: Aspirating fluid from the abdomen for examination, cultures, and cell counts. Complete blood count: May show elevated white blood cells. Blood cultures: To identify any causative bacteria. Management Immediate hospitalisation. Administer broad-spectrum intravenous antibiotics – later tailored based on culture results. Surgery to treat the root cause, e.g., repair of a ruptured organ. Fluid resuscitation and possible nutritional support. Analgesics for pain. Complications Septic shock: Life-threatening decrease in blood pressure due to sepsis. Abscess formation in the abdomen. Organ failure. Adhesions leading to bowel obstruction in the long term. Early recognition and intervention in peritonitis are crucial given its potential severity and life-threatening complications.