Peritoneitis

Peritoneitis, more correctly called peritonitis, is inflammation of the peritoneum, the lining of the abdominal cavity. It is usually due to infection but can be caused by chemical irritation. It presents with acute abdominal pain and tenderness, often with fever and tachycardia. It is classified as primary, secondary, or tertiary.

Primary peritonitis occurs without an intra‑abdominal source and is common in cirrhosis with ascites or nephrotic syndrome. Secondary peritonitis results from perforation or inflammation of an intra‑abdominal organ, such as appendicitis, diverticulitis, perforated ulcer, trauma, or postoperative leak. Noninfectious chemical peritonitis may follow bile leakage or dialysis solutions.

Symptoms include sudden severe abdominal pain, guarding, abdominal distension, and reduced bowel sounds. Systemic signs such as fever, rapid heart rate, dehydration, and malaise may be present. In severe cases the abdomen becomes rigid and sepsis or shock can develop.

Evaluation relies on history and exam, supported by labs and imaging. White blood cell count and inflammatory markers are often elevated. In ascites, diagnostic paracentesis analyzes cell count, Gram stain, and culture; a polymorphonuclear leukocyte count above 250 cells/µL supports infection. Ultrasound or CT helps identify the source.

Treatment requires prompt intravenous fluids and broad‑spectrum antibiotics with timely source control. Common empiric regimens cover enteric Gram‑negative and anaerobic bacteria; regimens are tailored to local resistance and patient factors. Surgical or interventional radiology procedures may be needed for perforation, abscess, or obstruction. In cirrhotics, albumin is used to prevent renal failure.

Prognosis depends on cause, comorbidities, and speed of treatment; mortality remains high when therapy is delayed. Prevention focuses on treating underlying intra‑abdominal disease, sterile technique in peritoneal dialysis, vaccination where appropriate, and managing cirrhosis and ascites to reduce spontaneous bacterial peritonitis risk.