The evaluation of peritonitis begins with a history and physical exam.

Physical findings in someone with peritonitis may include:

• Fever
• Severe abdominal tenderness
• Rigid abdominal muscles
• Low blood pressure:
• Systolic blood pressure (top number) below 90
• Rapid pulse:
• Over 120 beats per minute

Tests are necessary to evaluate peritonitis.

Tests that may be used to evaluate peritonitis include:

• Cultures of the fluid inside the abdomen
• Complete blood count
• Blood cultures
• Chest x-ray
• Abdominal x-ray
• CT scanning of the abdomen