Congenital lung anomalies

Embryology & Overview - Lung Budding Gone Wild

• Origin: Respiratory diverticulum (lung bud) arises from the ventral foregut endoderm around week 4.
• Separation: The tracheoesophageal septum partitions the foregut into the dorsal esophagus and ventral trachea.
• Errors: Faulty partitioning leads to tracheoesophageal fistulas (TEF); abnormal budding causes bronchogenic cysts, sequestration, or agenesis.

⭐ Most common TEF: Esophageal atresia with a distal tracheoesophageal fistula (~85% of cases). This presents with polyhydramnios in utero, and choking/aspiration upon first feeding.

Pulmonary Sequestration - Rogue Lung Tissue

• Non-functional lung tissue with no connection to the bronchial tree.
• Receives arterial blood from systemic circulation (e.g., aorta), not pulmonary arteries.

• Intralobar (ILS):

  • More common (~85%).
  • Located within a normal lung lobe; shares visceral pleura.
  • Presents in adults with recurrent, localized pneumonia.
  • Venous drainage: Pulmonary veins.

• Extralobar (ELS):

  • Less common (~15%).
  • Located outside normal lung; has its own pleura.
  • Presents in infants, often with other anomalies (e.g., diaphragmatic hernia).
  • Venous drainage: Systemic veins (e.g., azygous).

⭐ The hallmark is an anomalous systemic artery supplying the sequestered segment, most commonly arising from the thoracic or abdominal aorta.

CPAM & Bronchogenic Cysts - Airway Malformation Mayhem

• Congenital Pulmonary Airway Malformation (CPAM):
  • Hamartomatous mass of cystic lung tissue; communicates with airway.
  • Presents as neonatal respiratory distress or recurrent infections.
  • CXR/CT shows a multicystic, air-filled lesion.
• Bronchogenic Cyst:
  • Arises from abnormal ventral foregut budding; does NOT communicate with airway.
  • Typically a fluid-filled, unilocular cyst in the mediastinum.
  • Can cause compressive symptoms (dyspnea, dysphagia).

⭐ While most CPAMs are benign, they carry a risk of malignant transformation to pleuropulmonary blastoma, especially Type 4.

Congenital Lobar Overinflation - One-Way Air Trap

• Pathophysiology: Ball-valve bronchial obstruction leads to progressive lobar air-trapping and hyperinflation. Often from defective bronchial cartilage (~50% of cases) or extrinsic compression.
• Presentation: Neonatal respiratory distress, wheezing, cyanosis.
• Common Lobes: LUL > RML > RUL.
• Diagnosis:
  • CXR: Hyperlucent lobe, mediastinal shift away from the affected side, atelectasis of adjacent lobes.
  • CT confirms diagnosis.
• Management: Surgical lobectomy is the definitive treatment.

⭐ Unlike a simple pneumothorax, CLO causes severe mediastinal compression, risking cardiovascular collapse; it's a surgical emergency.

High‑Yield Points - ⚡ Biggest Takeaways

• Pulmonary sequestration is non-functional lung tissue lacking connection to the airway and pulmonary artery, receiving systemic arterial supply.
• Bronchogenic cysts are mediastinal masses from abnormal foregut budding that can become secondarily infected.
• CPAM is a hamartomatous lesion presenting with respiratory distress and a risk of malignant transformation.
• Pulmonary hypoplasia is frequently secondary to congenital diaphragmatic hernia or severe oligohydramnios.
• Intralobar sequestration drains to pulmonary veins; extralobar sequestration drains into the systemic venous system.