What is the best course of action for a 17-year-old male with a history of recent appendicitis with appendectomy (surgical removal of the appendix) and a previous dental abscess, who now presents with fatigue, malaise, fever, and leukocytosis (elevated white blood cell count)?

Post-Appendectomy Persistent Fever and Leukocytosis: Immediate Diagnostic Workup Required

This 17-year-old requires urgent contrast-enhanced CT abdomen/pelvis to evaluate for post-operative intra-abdominal abscess, which occurs in 3-20% of appendectomy cases and is the most likely cause of persistent fever, malaise, and leukocytosis 10 days post-operatively. 1, 2

Immediate Diagnostic Approach

Obtain contrast-enhanced CT abdomen and pelvis immediately as the primary diagnostic modality, which achieves sensitivities of 85.7-100% and specificities of 94.8-100% for identifying intra-abdominal collections. 3, 4 This imaging is critical because:

• Post-operative abscesses occur in 3-20% of appendectomy cases, with higher rates following perforated appendicitis 1
• Clinical diagnosis of intra-abdominal abscess (persistent fever, leukocytosis, malaise) lacks accuracy without cross-sectional imaging 5
• The 10-day timeframe is typical for post-appendectomy abscess presentation 1

Key laboratory assessments:

• Complete blood count with differential (already showing WBC 17.6) 4
• C-reactive protein level, which is significantly elevated in ongoing intra-abdominal infection 4
• Blood cultures if patient appears septic 6

Critical Connection: Recent Dental Abscess

The preceding dental abscess is highly relevant - bacteremia from oral flora (particularly Streptococcus viridans, anaerobes) can seed distant sites. 6 Consider:

• Septic arthritis or other metastatic infection from either the dental source or appendiceal perforation, as bacteremia from perforated appendicitis can cause distal bacterial seeding 7
• The combination of two recent infections within weeks suggests possible immunocompromise or inadequate source control

Management Algorithm Based on CT Findings

If CT Shows Post-Operative Abscess (Most Likely Scenario):

For abscesses ≥3 cm: Percutaneous catheter drainage (PCD) with IV antibiotics is first-line treatment, with success rates of 76-97%. 5 This approach:

• Achieves rapid clinical improvement 5
• Avoids reoperation in most cases 5
• Requires interventional radiology availability 5

If PCD is not available or fails: Laparoscopic drainage is preferred over open laparotomy for post-appendectomy abscesses not amenable to percutaneous approach. 1 Mean hospital stay after laparoscopic drainage is 6.5 days with no procedure-specific complications. 1

Antibiotic regimen for intra-abdominal abscess:

• Ceftriaxone 1-2g IV daily PLUS metronidazole 500mg IV every 8 hours 6, 8, 9
• This combination covers Escherichia coli, Klebsiella, Bacteroides fragilis, and Peptostreptococcus species commonly found in post-appendectomy abscesses 6
• Continue IV antibiotics until patient is afebrile and leukocytosis resolves 1, 2

Critical pitfall: In complicated appendicitis, cessation of IV antibiotics when fever or leukocytosis is present is strongly associated with intra-abdominal abscess development (p=0.013). 2 Do not convert to oral antibiotics or discontinue therapy while WBC remains elevated at 17.6. 2

If CT Shows No Abscess But Symptoms Persist:

Consider alternative diagnoses:

• Septic arthritis from bacteremic seeding (hip, shoulder, or other joints) - examine for joint pain, decreased range of motion 7
• Endocarditis from dental abscess bacteremia - obtain blood cultures, consider echocardiography if new murmur or persistent bacteremia 6
• Pelvic thrombophlebitis - CT venography may be needed 5
• Retained appendicolith or foreign body - review operative report 5, 9

If imaging is negative but clinical suspicion remains high: Diagnostic laparoscopy has both diagnostic and therapeutic value and should be performed. 4

Duration of Antibiotic Therapy

For complicated appendicitis with abscess: Continue IV antibiotics for minimum 5 days or until clinical resolution (afebrile, normalized WBC). 2 Prolonging antibiotics beyond 5 days in complicated appendicitis does not reduce infection rates, but premature discontinuation increases risk. 2

Monitor for treatment failure indicators:

• Persistent fever beyond 48-72 hours of appropriate drainage and antibiotics 5
• Rising or persistently elevated WBC count 2
• Worsening abdominal pain or peritoneal signs 5

Special Considerations for This Patient

The dental abscess history mandates:

• Blood cultures to rule out ongoing bacteremia 6
• Careful cardiac examination for endocarditis 6
• Joint examination for septic arthritis, which has been reported as a complication of perforated appendicitis 7

Age-specific factor: At 17 years old, this patient is at the transition between pediatric and adult care. Laparoscopic drainage has been well-characterized as safe and effective in the pediatric population for post-appendectomy abscesses. 1

Monitoring and Follow-Up

Close surveillance required:

• Clinical and radiological surveillance at 12-24 hour intervals if managed non-operatively 5
• Daily assessment of fever curve, WBC trend, and clinical examination 2
• If patient develops persistent abdominal pain, worsening fever, or signs of shock, surgical treatment cannot be postponed 5

Failure of non-operative management: Patients who fail conservative treatment should proceed to surgery expeditiously. 5