What are the signs and symptoms of peritonitis?

Signs of Peritonitis

Peritonitis presents with abdominal pain and tenderness (occurring in 74-95% of patients), typically accompanied by rebound tenderness and guarding, along with systemic signs of inflammation including fever, tachycardia, and altered bowel sounds. 1, 2

Cardinal Physical Examination Findings

Abdominal Signs

• Abdominal rigidity is the most specific finding that strongly suggests peritonitis 2
• Rebound tenderness and guarding accompany the pain and tenderness in the majority of cases 1, 2
• Decreased or absent bowel sounds due to developing ileus 3, 2
• Abdominal distension occurs, with isolated distension seen in 6.6% of patients 1, 2

Systemic Inflammatory Signs

• Fever >38.5°C is present in approximately 38% of patients 3, 1, 2
• Tachycardia occurs in 62.5% of patients (note: bradycardia is NOT an expected finding) 1, 2
• Tachypnea as part of the systemic inflammatory response 2
• Rigors (uncontrollable shaking with chills) 3

Signs of Severe Disease and Complications

• Hemodynamic instability including hypotension and signs of septic shock 3, 1
• Hypoperfusion signs: lactic acidosis, oliguria (decreased urinary output), and altered mental status 1, 2
• Hepatic encephalopathy may develop, particularly in patients with underlying liver disease 3, 2
• Worsening renal function 3, 2

Associated Gastrointestinal Symptoms

• Nausea and vomiting reported in 35% of patients 2
• Ileus symptoms: vomiting and absent passage of stool 3, 2
• Diarrhea may occur 3
• Rectal bleeding is observed in 15% of patients 1

Laboratory Findings

• Marked leukocytosis (white blood cell count >15 × 10⁹/L) with left shift (band neutrophils >20%) 3, 1, 2
• Elevated serum lactate indicating tissue hypoperfusion 3, 1, 2
• Rise in serum creatinine (>50% above baseline) 3, 1, 2
• Elevated C-reactive protein (CRP) levels 1, 2

Specific to Spontaneous Bacterial Peritonitis (SBP)

• Ascitic fluid neutrophil count >250/mm³ is diagnostic for SBP 3, 1
• Low ascitic fluid glucose (<50 mg/dL) suggests secondary peritonitis 1

Imaging Findings

• CT scan has the highest sensitivity and specificity for detecting peritonitis 1
• Free air on plain abdominal radiograph indicates perforation 1
• CT may show: free fluid and air, bowel wall thickening, pericolonic fat inflammation, and ascites 3, 1
• Ultrasound can identify free fluid in the abdomen, particularly useful in resource-limited settings 1

Critical Clinical Pitfalls

A common pitfall is that physical signs may be subtle in early peritonitis, requiring high clinical suspicion. 2 The classic presentation of "pain out of proportion to physical examination findings" may be present early, making diagnosis challenging 2. Delayed diagnosis and treatment significantly increases mortality rates, especially in diffuse peritonitis. 1, 4

Distinguishing Primary from Secondary Peritonitis

• Primary (spontaneous) peritonitis: typically one organism on culture, occurs without GI tract disruption, common in cirrhotic patients 3, 1
• Secondary peritonitis: multiple organisms on culture, very high ascitic neutrophil count, high ascitic protein, localized abdominal symptoms, inadequate response to therapy 3, 1
• When secondary peritonitis is suspected, prompt CT scanning and early surgical consultation are essential 3