The underlying pathophysiology of congenital diaphragmatic hernia (CDH) is which of the following?

• A. Abdominal Wall Hypoplasia
• B. Persistent Pulmonary Hypertension (PPHN)
• C. Respiratory Distress Syndrome (RDS)
• D. Pulmonary Edema

Answer: (B)

Congenital diaphragmatic hernia causes pulmonary hypoplasia from compression of the developing lungs by abdominal organs herniating into the chest. The resulting lungs are small and have abnormal pulmonary vasculature, leading to high pulmonary vascular resistance. After birth, this persistent high PVR drives right-to-left shunting through fetal channels (foramen ovale and ductus arteriosus) and severe hypoxemia—what we call persistent pulmonary hypertension. This physiologic cascade best explains CDH’s underlying pathophysiology.

Abdominal wall hypoplasia isn’t the primary issue here. Respiratory distress syndrome stems from surfactant deficiency rather than the mechanical restriction and hypoplasia of the lungs, and pulmonary edema is a possible consequence rather than the fundamental problem.