What are the clinical signs of peritonitis?

Clinical Signs of Peritonitis

Peritonitis presents with abdominal pain and tenderness in 74-95% of patients, typically accompanied by rebound tenderness, guarding, and abdominal rigidity—the latter being the most specific physical finding that strongly suggests the diagnosis. 1, 2

Primary Abdominal Findings

The hallmark physical examination findings include:

• Abdominal rigidity is the key clinical feature with the highest specificity for peritonitis 1, 2
• Rebound tenderness and guarding are present in 82.5% of patients 3
• Abdominal pain and tenderness occur in 74-95% of cases and represent the most common presenting symptom 1, 2, 3
• Abdominal distension is observed, with isolated distension seen in 6.6% of patients 1, 2, 3
• Decreased or absent bowel sounds develop due to ileus formation 1, 2, 3

Systemic Signs and Vital Sign Changes

Peritonitis triggers a systemic inflammatory response with characteristic vital sign abnormalities:

• Tachycardia is observed in 62.5% of patients—this is the expected cardiovascular response, not bradycardia 1, 2, 3
• Fever greater than 38.5°C is present in approximately 38% of cases 1, 2, 3
• Hypotension indicates progression to septic shock and represents a critical finding requiring immediate intervention 2, 3
• Tachypnea occurs as part of the systemic inflammatory response 2, 3

Gastrointestinal Symptoms

• Nausea and vomiting are reported in 35% of patients 2, 3
• Absence of defecation and other ileus symptoms develop as peritonitis progresses 1, 3
• Rectal bleeding is observed in 15% of cases 1, 3

Laboratory Abnormalities

Laboratory findings support the diagnosis but should not delay clinical decision-making:

• Leukocytosis occurs in 40% of patients, often with left shift (band neutrophils >20%) 1, 3
• Elevated C-reactive protein (CRP) levels are typically observed 1, 3
• Elevated serum lactate indicates tissue hypoperfusion and correlates with severity 1, 3
• Increased serum creatinine (>50% above baseline) suggests developing renal dysfunction 1, 3
• Elevated procalcitonin is particularly significant in delayed presentations beyond 12 hours 3

Signs of Organ Dysfunction and Complications

As peritonitis progresses, watch for:

• Oliguria and decreased urinary output indicating renal failure 2, 3
• Altered mental status from hypoperfusion, lactic acidosis, or hepatic encephalopathy 1, 2, 3
• Hemodynamic instability progressing to multi-organ failure 1, 3
• Worsening liver function especially concerning in cirrhotic patients 2, 3

Critical Pitfalls to Avoid

• Physical signs may be subtle or take several hours to develop, particularly in small bowel injury, requiring serial examinations to improve diagnostic accuracy 3
• Peritoneal signs can be masked by distracting injuries, head injuries, spinal cord injuries, or abdominal wall trauma 3
• "Pain out of proportion to physical examination findings" may be present in early peritonitis, making diagnosis challenging and requiring high clinical suspicion 2, 3
• Delayed diagnosis beyond 24 hours significantly increases mortality rates—time is critical, with every delay worsening outcomes 3, 4
• The overall mortality is 6% but rises dramatically to 35% in patients who develop severe sepsis 4