Congenital pulmonary airway malformation

A developmental abnormality of terminal bronchioles causing cystic or solid lung lesions.

Types (prenatal relevance)

Type	Ultrasound appearance	Key feature
Macrocystic	Large cysts (>5 mm)	Few large cysts
Microcystic	Solid echogenic mass	Tiny cysts not individually seen
Mixed	Both	Variable

Radiological features (prenatal ultrasound)

• Echogenic lung mass
• Cystic or solid
• Usually unilateral

May cause:

• Mediastinal shift
• Hydrops
• Polyhydramnios

Important measurement:

CVR (CPAM Volume Ratio); CVR > 1.6 → high hydrops risk

Prognosis of CPAM

Finding	Prognosis
Small lesion	Often regresses
Large lesion	Risk of hydrops
Hydrops present	Poor prognosis
No hydrops	Usually good survival

Many lesions shrink after 28–30 weeks.

Differential Diagnosis

A. Bronchopulmonary sequestration

Systemic arterial supply from aorta

Ultrasound features:

• Homogeneous echogenic mass
• Usually left lower lobe
• Feeding vessel from aorta
• May have pleural effusion

B. Congenital diaphragmatic hernia

Ultrasound clues:

• Abdominal organs in chest
• Stomach in thorax
• Mediastinal shift
• Small abdominal circumference

C. Hybrid lesions

Combination:

• CPAM + sequestration

Seen with:

• Cystic mass
• Systemic vessel

D. Congenital lobar emphysema

Usually postnatal diagnosis, but prenatal: echogenic lung, hyperinflated lobe

3. SCIMITAR Syndrome

Radiological features: curved anomalous vein resembling a scimitar sword

Prenatal ultrasound clues:

• Hypoplastic right lung
• Mediastinal shift to right
• Abnormal pulmonary venous drainage
• Possible right heart enlargement

Postnatal X-ray hallmark:

Curved vein draining into: inferior vena cava

Associated anomalies

• Right lung hypoplasia
• Cardiac anomalies
• Systemic arterial supply to lung

4. CHAOS

Congenital high airway obstruction syndrome

Etiology

• Laryngeal atresia
• Tracheal atresia

Pathophysiology

• Airway blocked → fluid trapped → lungs enlarge massively

Radiological features

Classic ultrasound pattern:

• Bilaterally enlarged echogenic lungs
• Flattened or inverted diaphragm
• Dilated trachea and bronchi
• Small compressed heart
• Ascites
• Hydrops

Symmetric lung enlargement is key.

MRI features:

• Exact level of obstruction
• Airway dilation

Feature	CPAM	Sequestration	CHAOS	CDH	Scimitar
Lung lesion	Yes	Yes	Diffuse	Herniated organs	Small lung
Laterality	Unilateral	Usually unilateral	Bilateral	Usually unilateral	Right-sided
Systemic artery	No	Yes	No	No	Sometimes
Airway dilation	No	No	Yes	No	No
Diaphragm	Normal	Normal	Inverted	Defect	Normal
Mediastinal shift	Yes	Yes	Minimal	Yes	Rightward

Key pattern recognition

• Unilateral cystic/solid mass → CPAM vs sequestration
• Systemic feeding vessel → sequestration
• Bilateral enlarged lungs + airway dilation → CHAOS
• Small right lung + abnormal pulmonary vein → Scimitar

Specific scenario interpretation

Findings:

• Entire left lung hyperinflated
• Diffusely echogenic
• Dextrocardia (likely from mass effect)
• Not limited to a single lobe

This pattern fits better with proximal airway obstruction than with CPAM.

Most likely considerations:

• Congenital bronchial atresia
• Mucus plug obstruction
• Localized form of Congenital high airway obstruction syndrome
• Rarely congenital lobar emphysema

Congenital bronchial atresia

Mechanism:

• Proximal bronchus obstructed
• Distal lung traps fluid
• Lung becomes enlarged, echogenic, hyperinflated

Ultrasound features suggesting bronchial obstruction

• Uniformly echogenic entire lung
• Lung enlargement
• Mediastinal shift (→ dextrocardia)
• Dilated distal bronchi (sometimes visible)
• No systemic arterial supply

Mucus plug specifically?

• Obstruction is temporary
• Lung size fluctuates
• Later regression occurs

Mucus plug behaves like: functional bronchial atresia

Localized CHAOS

Classic CHAOS shows:

• Bilateral enlarged lungs
• Inverted diaphragm
• Dilated trachea
• Hydrops

If only left lung affected, this favors: bronchial obstruction, NOT full CHAOS.

Congenital lobar emphysema

• Single lobe massively overexpanded
• Progressive hyperinflation

Usually postnatal diagnosis.

Fetal MRI can show:

• Dilated bronchi
• Level of obstruction
• Whole lung involvement
• Airway continuity

Natural evolution patterns

• Stable lesion
• Partial regression
• Complete resolution
• Rare progression to hydrops

Conclusion

Whole left lung hyperinflated + echogenic + dextrocardia

Most likely: Proximal left bronchial obstruction (possibly mucus plug–related)

Less likely:

• CPAM
• Sequestration
• CHAOS (unless bilateral)