What is the recommended evaluation and initial management for an adult presenting with acute abdominal pain, guarding, fever, tachycardia and signs of sepsis suggestive of peritonitis?

Management of Acute Peritonitis

Patients presenting with acute abdominal pain, guarding, fever, tachycardia, and signs of sepsis suggestive of diffuse peritonitis require emergency surgical intervention as soon as possible, even while resuscitative measures continue, combined with immediate broad-spectrum antibiotics and aggressive fluid resuscitation. 1, 2

Initial Diagnostic Evaluation

Clinical Assessment

• Routine history and physical examination identify most patients requiring intervention, though classic peritoneal signs may be less reliable in certain populations 1
• Look specifically for: diffuse abdominal pain, involuntary guarding, rebound tenderness, and absent bowel sounds 1
• Physical examination findings are less sensitive in postoperative patients, immunosuppressed patients, those with altered mental status, or spinal cord injury - maintain high index of suspicion in these groups 1, 3

Imaging

• CT scan is the imaging modality of choice for patients not proceeding immediately to surgery, with 97.2% diagnostic accuracy 1, 3
• Plain radiography (66.2% sensitivity) and ultrasound (44.3% sensitivity) are significantly less accurate 3
• Skip imaging entirely in patients with obvious diffuse peritonitis who require immediate laparotomy 1

Immediate Resuscitation (Concurrent with Other Measures)

Fluid Resuscitation

• Begin rapid intravascular volume restoration immediately upon recognition of peritonitis 1, 4
• For septic shock: initiate resuscitation the moment hypotension is identified 1
• Volume depletion is universal due to fever-induced tachypnea, third-spacing, and poor oral intake 1

Antimicrobial Therapy Timing

• For septic shock: administer antibiotics within 1 hour of recognition 1
• For patients without shock: start antibiotics in the emergency department, ideally within 8 hours 1
• Maintain adequate antimicrobial levels during surgery - may require additional dosing immediately before the procedure 1

Antimicrobial Selection

Empiric Coverage

• Target polymicrobial flora: Gram-negative, Gram-positive, and anaerobic bacteria 4
• For non-critically ill, immunocompetent patients with adequate source control: piperacillin/tazobactam 3.375g IV every 6 hours 4, 5
• For septic shock or critically ill patients: meropenem, doripenem, or imipenem/cilastatin 4
• For high risk of ESBL-producing organisms: ertapenem or eravacycline 4

Culture Guidance

• Obtain intraoperative cultures from the infection site - at least 1 mL of fluid or tissue in appropriate transport 1
• Obtain cultures routinely in higher-risk patients, particularly those with prior antibiotic exposure 1
• Consider fungal coverage (echinocandin preferred) for hospital-acquired infections in critically ill or severely immunocompromised patients 4, 6

Source Control Strategy

Timing of Surgery

• Emergency surgery should proceed as soon as possible for diffuse peritonitis, without waiting for complete physiologic stabilization 1, 2
• Delaying surgery beyond 24 hours is associated with increased mortality 1
• Continue resuscitative measures during the surgical procedure 1, 2

Surgical Objectives

• Drain all infected foci 1, 4
• Control ongoing peritoneal contamination through diversion or resection 1, 4
• Restore anatomic and physiological function to the extent feasible 1, 4
• Perform extensive peritoneal lavage 7

Surgical Approach Selection

• For perforated diverticulitis with diffuse peritonitis in critically ill patients: Hartmann's procedure 2, 4
• For perforated peptic ulcer: simple closure with omental patch for small perforations, or resection with primary anastomosis when appropriate 2
• Percutaneous drainage is preferable for well-localized abscesses (not applicable to diffuse peritonitis) 1

Relaparotomy Strategy

• Perform relaparotomy on-demand only - approximately 90% of patients achieve source control with single operation 7
• Mandatory/scheduled relaparotomy is NOT recommended unless intestinal discontinuity, inability to close fascia, or intra-abdominal hypertension exists 1, 4
• Planned relaparotomy and open packing increase morbidity and are rarely indicated 7

Antibiotic Duration

• For adequate source control in non-critically ill patients: 3-5 days 4
• For immunocompromised or critically ill patients with adequate source control: up to 7 days 4
• Standard duration for most intra-abdominal infections: 7-10 days 5

Critical Pitfalls to Avoid

• Delaying surgery while attempting complete stabilization - this dramatically increases mortality 1, 2, 8
• Delaying antibiotics - each hour of delay in septic shock worsens outcomes 1, 8
• Inadequate source control at initial operation - failure to drain all infected foci or control contamination 1
• Relying on physical examination alone in high-risk populations (postoperative, immunosuppressed, elderly) 1, 3
• Using plain films or ultrasound when CT is available and patient is stable enough for imaging 3
• Inadequate antimicrobial levels during the perioperative period 2