🫁 CPAM vs CDH: The Most Important Ultrasound Clues

Fetal thoracic masses can be challenging to interpret on ultrasound.

Two of the most commonly confused conditions are:

• CPAM (Congenital Pulmonary Airway Malformation)
• CDH (Congenital Diaphragmatic Hernia)

Although both may present as an abnormal structure within the fetal chest,

their origin, prognosis, and management are entirely different.

Understanding the key ultrasound clues is critical.

1️⃣ Start With the Stomach Position

This is the most important first step.

🔍 Ask yourself:

Where is the stomach?

• If the stomach is seen inside the chest → strongly suspect CDH
• If the stomach remains in the abdomen → consider CPAM

In CDH, abdominal organs herniate into the thoracic cavity.

In CPAM, the abnormality arises from lung tissue itself.

2️⃣ Evaluate the Diaphragm

In CDH:

• The diaphragm may appear discontinuous.
• The abdominal–thoracic boundary looks disrupted.

In CPAM:

• The diaphragm remains intact.
• The mass is located within the lung.

Diaphragm continuity is a crucial differentiating feature.

3️⃣ Look for Bowel Peristalsis

In CDH:

• You may observe bowel movement within the thoracic cavity.

In CPAM:

• No peristalsis is present within the lung mass.

If you see moving bowel loops in the chest, think CDH.

4️⃣ Assess Liver Position

Especially in right-sided CDH:

• The liver may herniate into the thorax.

In CPAM:

• The liver remains in its normal abdominal location.

Liver herniation significantly affects prognosis in CDH.

5️⃣ Use Color Doppler When Needed

• CPAM: no systemic feeding artery
• Bronchopulmonary sequestration (BPS): systemic feeding artery from the aorta
• CDH: bowel vascular patterns may be seen

Color Doppler helps refine the diagnosis.

6️⃣ Prognostic Differences

CPAM

• May stabilize or regress after 26–28 weeks
• Risk depends on lesion size (CVR)
• Many cases have good postnatal outcomes

CDH

• Associated with pulmonary hypoplasia
• Requires LHR assessment
• Prognosis depends on lung development and liver position

🔑 The Core Clinical Message

When you detect a thoracic mass on fetal ultrasound:

1. Check the stomach location.
2. Confirm diaphragm integrity.
3. Look for bowel peristalsis.
4. Evaluate liver position.
5. Consider Doppler findings.

In most cases,

the stomach location will guide you toward the correct diagnosis.