What is the recommended initial evaluation and management for a patient with physical exam findings suggestive of acute appendicitis?

Initial Evaluation and Management of Suspected Acute Appendicitis

For non-pregnant adults with physical exam findings suggestive of acute appendicitis, obtain CT abdomen/pelvis with IV contrast as the initial imaging modality, and initiate broad-spectrum antibiotics immediately upon diagnosis without waiting for imaging confirmation. 1, 2

Immediate Actions Upon Presentation

• Start broad-spectrum antibiotics immediately upon clinical suspicion without waiting for imaging confirmation, as early administration reduces complications and mortality. 2
• Recommended first-line antibiotic regimens include:
  • Cefotaxime 2g IV every 8 hours plus metronidazole 500mg IV every 6 hours 2
  • Alternative: Piperacillin-tazobactam monotherapy 3
  • For beta-lactam allergy: Ciprofloxacin 400mg IV every 8 hours plus metronidazole 500mg IV every 6 hours 2
• Provide opioid analgesia without delay—pain control does not mask peritoneal signs or delay necessary intervention. 2, 4

Diagnostic Imaging Strategy

Non-Pregnant Adults

• CT abdomen/pelvis with IV contrast is the gold standard initial imaging modality, achieving sensitivity of 96-100% and specificity of 93-95%. 1, 5
• IV contrast alone is sufficient—oral contrast is unnecessary and delays diagnosis by 40 minutes to 2+ hours without improving accuracy. 1, 5
• If CT is negative but clinical suspicion remains high, consider observation with supportive care ± antibiotics, or surgical intervention if suspicion is very high. 1

Special Populations

• Children and adolescents: Ultrasound is the initial imaging modality (sensitivity 76%, specificity 95%), followed by CT or MRI if inconclusive. 1, 6
• Pregnant patients: Ultrasound first, then MRI without IV contrast if equivocal (MRI sensitivity 94%, specificity 96%). 1
• Point-of-care ultrasound (POCUS) by experienced emergency physicians or surgeons shows superior accuracy (sensitivity 91%, specificity 97%) and should be considered first-line when available. 1, 6

Risk Stratification Based on Imaging

Uncomplicated Appendicitis

• CT findings: Appendiceal diameter ≥7mm without appendicolith, abscess, or perforation. 3
• Non-operative management (NOM) with antibiotics alone is appropriate for selected patients, with success rates of 70-78% at one year. 2, 3
• Critical contraindication to NOM: Presence of appendicolith—failure rate exceeds 40-60% and mandates surgical intervention. 2, 3
• Other high-risk CT findings requiring surgery: appendiceal diameter >13mm, mass effect, extraluminal air, or abscess. 3, 7

Complicated Appendicitis

• CT findings: Appendicolith, abscess, extraluminal air, appendiceal wall enhancement defect, or periappendiceal fat stranding. 1, 6
• Urgent surgical consultation is mandatory—laparoscopic or open appendectomy should be performed as soon as reasonably feasible. 2, 7
• For abscess >3cm: Consider percutaneous drainage plus antibiotics if accessible, followed by interval appendectomy. 2, 7
• Escalate antibiotics to imipenem-cilastatin 1g IV every 8 hours, meropenem 1g IV every 8 hours, or piperacillin-tazobactam 4.5g IV every 6 hours. 2

Clinical Decision Algorithm

1. High clinical suspicion (right lower quadrant pain, fever, leukocytosis, peritoneal signs):

   • Start antibiotics immediately 2
   • Obtain CT with IV contrast (adults) or ultrasound (children/pregnant) 1
   • Surgical consultation if imaging confirms appendicitis 2, 7

2. Intermediate clinical suspicion (atypical presentation):

   • Obtain imaging before surgical consultation 1
   • Use clinical scoring systems (Alvarado, AIR, AAS) to guide decision-making 6, 4

3. Low clinical suspicion:

   • Consider discharge with 24-hour follow-up 6
   • Avoid imaging in very low-risk patients 6

Duration of Antibiotic Therapy

• Non-operative management: IV antibiotics for minimum 48 hours, then oral antibiotics for total duration of 7-10 days. 2
• Post-appendectomy: Duration varies based on perforation status and source control adequacy. 2

Critical Pitfalls to Avoid

• Never attempt non-operative management in patients with appendicolith—failure rate exceeds 40-60%. 2, 3
• Do not delay antibiotics waiting for imaging confirmation—start immediately upon clinical suspicion. 2
• Do not order oral contrast with CT—it delays diagnosis without improving accuracy. 1, 5
• Do not dismiss appendicitis based on negative imaging alone if clinical suspicion remains high—consider observation or surgical consultation. 1
• In elderly patients, maintain high index of suspicion—atypical presentations are common and mortality rates are higher. 1, 6
• For patients ≥40 years old managed non-operatively, obtain colonoscopy and interval CT after recovery to exclude appendiceal neoplasm. 2

Special Considerations

• Young males with high clinical suspicion: Some surgeons proceed directly to diagnostic laparoscopy without imaging, though this approach requires experienced surgical judgment. 1
• Pregnant patients: Peritoneal signs may be less reliable due to anatomic displacement—rely heavily on imaging. 6
• Immunosuppressed patients: Proceed directly to surgical intervention to minimize complication risk. 7