What are the signs and symptoms of peritonitis?

Signs and Symptoms of Peritonitis

Peritonitis presents with abdominal pain and tenderness in 74-95% of patients, typically accompanied by rebound tenderness and guarding, with abdominal rigidity being a key clinical feature that strongly suggests the diagnosis. 1, 2

Local Abdominal Findings

Physical examination reveals:

• Abdominal pain and tenderness occurring in 74-95% of cases 1, 2
• Rebound tenderness and guarding present in 82.5% of patients 3
• Abdominal rigidity - a critical finding that strongly indicates peritonitis 2
• Abdominal distension seen in 6.6% as an isolated finding, but more commonly as part of the overall presentation 1, 2
• Decreased bowel sounds due to developing ileus 1, 2

Systemic Signs of Inflammation

Cardiovascular and temperature changes include:

• Tachycardia observed in 62.5% of patients (not bradycardia) 1, 2, 3
• Fever greater than 38.5°C present in 38% of cases 1, 2, 3
• Hypotension indicating progression to septic shock 2
• Tachypnea as part of the systemic inflammatory response 2

Gastrointestinal Symptoms

Associated GI manifestations:

• Nausea and vomiting reported in 35% of patients 2
• Absence of defecation and other ileus symptoms 4, 2
• Diarrhea may occur 4
• Rectal bleeding observed in 15% of cases 1, 3

Laboratory Abnormalities

Key laboratory findings include:

• Leukocytosis present in 40% of patients, often with left shift (band neutrophils >20%) 1, 2, 3
• Elevated C-reactive protein (CRP) levels 1, 2, 3
• Increased serum lactate indicating tissue hypoperfusion 1, 2
• Elevated serum creatinine (>50% above baseline) suggesting renal dysfunction 1, 2
• Elevated procalcitonin (PCT) particularly in delayed presentations beyond 12 hours 3

Specific Findings for Spontaneous Bacterial Peritonitis (SBP)

• Ascitic fluid neutrophil count >250/mm³ is diagnostic for SBP 4, 1
• Low ascitic fluid glucose (<50 mg/dL) suggests secondary peritonitis 1

Signs of Organ Dysfunction and Complications

Critical complications to monitor:

• Hepatic encephalopathy may develop, particularly in cirrhotic patients 4, 2
• Renal failure manifesting as oliguria and decreased urinary output 4, 1, 2
• Shock with signs of hypoperfusion including lactic acidosis and altered mental status 4, 2
• Worsening liver function especially in patients with underlying cirrhosis 4, 2
• Hemodynamic instability progressing to multi-organ failure 1, 2

Clinical Pitfalls

Important caveats to avoid missed diagnosis:

• Physical signs may be subtle or minimal, particularly in elderly or unconscious patients who may have severe disease despite minimal examination findings 3
• A small proportion (5%) of patients may remain asymptomatic despite peritonitis 3
• Postoperative peritonitis shows particularly high mortality due to unspecific symptoms 5
• Delayed diagnosis beyond 24 hours significantly increases mortality rates and the need for more invasive treatments 4, 2, 3
• The classic presentation of "pain out of proportion to physical examination findings" may be present in early peritonitis, making diagnosis challenging 2

Imaging Findings

When peritonitis is suspected:

• CT scan has the highest sensitivity and specificity (>90% accuracy) for detecting peritonitis and should be performed in stable patients with suspected diagnosis 4, 3
• Free air on plain abdominal radiograph indicates perforation, though sensitivity is lower than CT 1, 3
• Ultrasonography may show free fluid in the abdomen and can be valuable in resource-limited settings 1, 2