In a 9‑month‑old infant with a known infradiaphragmatic pulmonary sequestration presenting with fever, leukocytosis, elevated C‑reactive protein and a left lower‑lobe infiltrate, what complications (such as infection or enlargement) should be considered and how should the sequestration be managed?

Management of Pulmonary Sequestration with Acute Infection

This infant requires immediate surgical consultation for evaluation of the pulmonary sequestration, as secondary infection in underlying pulmonary anomalies like sequestration mandates consideration of definitive surgical resection 1.

Critical Complications to Anticipate

Can the Sequestration Become Infected?

Yes, absolutely. Pulmonary sequestrations are highly susceptible to infection because:

• The sequestered tissue lacks normal bronchial communication and drainage
• Stagnant secretions accumulate within the abnormal tissue
• The systemic arterial blood supply creates an environment prone to abscess formation
• Recent case reports demonstrate that sequestrations commonly present as lung abscesses or necrotizing pneumonia 2, 3, 4, 5

Your infant's presentation—with high fever, elevated inflammatory markers (CRP 95.9 mg/L, leukocytosis 15,600), and a left lower lobe infiltrate overlying the known sequestration—strongly suggests infection of the sequestration itself, not just adjacent pneumonia.

Can the Sequestration Enlarge?

The sequestration itself does not typically "grow," but:

• Infected sequestrations develop abscesses that can appear as enlarging masses
• Surrounding inflammation and edema create the appearance of expansion
• Vascular engorgement during acute infection may increase the lesion size temporarily

Immediate Management Algorithm

1. Aggressive Antibiotic Therapy

• Start IV antibiotics immediately covering Streptococcus pneumoniae (most common) 1, 6
• For this infant with known structural anomaly, use broader spectrum coverage to include:
  • Gram-positive cocci (including MRSA if risk factors present)
  • Gram-negative organisms
  • Anaerobes (sequestrations can harbor mixed flora)
• Continue IV antibiotics until clinical improvement, then transition to oral for 1-4 weeks minimum 6

2. Enhanced Imaging

• Obtain chest CT with IV contrast immediately to:
  • Differentiate simple pneumonia from abscess formation within the sequestration 1
  • Identify the anomalous systemic arterial supply (typically from descending aorta) 2, 3, 4
  • Assess for complications (necrotizing pneumonia, pleural involvement)
  • Guide surgical planning
• Ultrasound can supplement but CT angiography is definitive 7

3. Surgical Consultation

Obtain thoracic surgery consultation now, not later. The PIDS/IDSA guidelines explicitly state: "Patients with a secondary abscess due to an underlying pulmonary anomaly or lesion (eg, congenital cystic adenomatoid malformation, pulmonary sequestration) require surgical consultation for evaluation of long-term management of the lesion, and to determine whether surgical resection is required" 1.

While most simple lung abscesses resolve with antibiotics alone, sequestrations are different—they represent structurally abnormal tissue that will remain a nidus for recurrent infection even after this acute episode resolves.

Monitoring During Acute Phase

Clinical Parameters

• Tachycardia (128-190 bpm) and tachypnea (50/min with fever) indicate significant systemic inflammation 1
• Monitor for:
  • Worsening respiratory distress
  • Oxygen desaturation (currently normal SpO2 is reassuring)
  • Signs of sepsis progression
  • Development of pleural effusion/empyema

Red Flags Requiring Escalation

• Failure to defervesce within 48-72 hours of appropriate antibiotics
• Worsening respiratory status
• Development of pleural complications
• Hemodynamic instability
• These indicate possible abscess formation requiring drainage or urgent surgery 1

Definitive Management Considerations

Timing of Surgery

• Acute infection is NOT an absolute contraindication to surgery in sequestrations, unlike necrotizing pneumonia 1
• However, most surgeons prefer to:
  1. Treat acute infection medically first
  2. Allow inflammation to subside (typically 4-6 weeks)
  3. Perform elective resection once stable 3, 5
• Exception: If abscess develops and fails medical management, earlier intervention (CT-guided drainage or surgical resection) may be necessary 1

Surgical Approach

• For infradiaphragmatic sequestration: thoracoscopic resection is feasible and effective 7
• The anomalous systemic arterial supply must be identified and ligated to prevent life-threatening hemorrhage 2
• Complete resection is curative and prevents recurrent infections

Common Pitfalls to Avoid

1. Treating this as simple pneumonia: The underlying sequestration changes everything—this tissue will not "heal" normally and requires definitive management
2. Delaying CT imaging: You need to know if an abscess has formed, as this affects management urgency
3. Inadequate antibiotic duration: Structural lung disease requires prolonged therapy (minimum 1-4 weeks oral after IV course) 6
4. Missing the surgical window: Even if this episode resolves, the sequestration will cause recurrent problems—surgical planning should begin now
5. Underestimating hemorrhage risk: If surgery becomes necessary, the anomalous systemic arterial supply poses significant bleeding risk if not properly identified preoperatively 2

Prognosis

With appropriate antibiotic therapy and eventual surgical resection, the prognosis is excellent. The key is recognizing that this is not just pneumonia—it's an infected congenital anomaly that requires both immediate medical management and definitive surgical planning.