What Are Peritoneal Signs?
Peritoneal signs are physical examination findings that indicate peritoneal irritation or inflammation, most notably including abdominal rigidity, involuntary guarding, rebound tenderness, and significant abdominal tenderness on palpation. 1, 2
Core Physical Examination Findings
Abdominal rigidity is the most specific finding that strongly suggests the presence of peritonitis and represents involuntary contraction of the abdominal wall musculature in response to peritoneal inflammation. 2, 3
Involuntary guarding occurs when the abdominal muscles reflexively contract during palpation, distinguishing it from voluntary guarding where patients consciously tense their abdomen. 1
Rebound tenderness is elicited when sudden release of palpation pressure causes sharp pain, indicating parietal peritoneal irritation. This finding, along with tenderness, occurs in 74-95% of patients with peritonitis. 2, 3
Significant abdominal tenderness on palpation is a cardinal feature, though it may be diffuse or localized depending on whether peritonitis is generalized or localized. 1
Associated Clinical Findings
Beyond the classic triad of rigidity, guarding, and rebound tenderness, peritoneal signs encompass several other examination findings:
- Decreased or absent bowel sounds due to ileus from peritoneal inflammation 2
- Abdominal distension which occurs in approximately 6.6% of patients with isolated presentation 2
- Percussion tenderness throughout the abdomen in diffuse peritonitis 1
Important Clinical Caveats
The development of peritoneal signs may be significantly delayed in certain clinical scenarios, which is a critical pitfall to recognize. 1
In small bowel injuries, peritoneal signs tend to develop slowly because luminal contents have neutral pH, are enzymatically less active, and have relatively low bacterial load compared to colonic contents. 1
Bowel perforation from vascular injury resulting in ischemia and necrosis may cause peritoneal signs to take many hours to develop, as the perforation itself is a delayed consequence. 1
Peritoneal signs may be masked or difficult to assess in several patient populations:
- Patients with distracting injuries that draw attention away from abdominal findings 1
- Head and spinal cord injuries that mask pain perception 1
- Associated injuries of the abdominal wall, rib cage, and pelvic girdle that can mimic guarding 1
- Diabetic or immunosuppressed patients who may present with general decompensation without classic peritoneal signs 3
- Comatose or unconscious patients where physical examination is unreliable 1
Clinical Context and Accuracy
Serial examinations significantly improve diagnostic accuracy when peritoneal signs are equivocal or absent initially. 1 This is particularly important in non-operative management or observation protocols where the evolution of peritoneal signs over time helps confirm or exclude peritonitis. 1
The presence of peritoneal signs indicates leakage of intestinal contents or other irritating substances into the peritoneal cavity, though these signs may take several hours to fully manifest depending on the nature and location of the injury. 1
Hemodynamic instability accompanying peritoneal signs (hypotension, tachycardia in 62.5% of cases, altered mental status) indicates progression to sepsis or septic shock and demands immediate intervention. 2, 3