A newborn presented severe respiratory distress. On examination he was found to have scaphoid abdomen and absent breath sounds on left side of chest. The most likely diagnosis is:
**Core Concept**
Congenital diaphragmatic hernia (CDH) is a life-threatening condition in newborns characterized by a defect in the diaphragm, allowing abdominal organs to herniate into the thoracic cavity, compromising lung development and leading to respiratory distress.
**Why the Correct Answer is Right**
In CDH, the diaphragm's absence or weakness creates a communication between the thoracic and abdominal cavities, allowing abdominal contents (such as the stomach, small intestine, and liver) to migrate into the chest. This herniation compresses the developing lungs, leading to pulmonary hypoplasia and hypoxia. The clinical presentation of CDH includes respiratory distress, scaphoid abdomen (due to the displacement of abdominal contents into the chest), and absent breath sounds on the affected side. The scaphoid abdomen is a result of the displacement of the abdominal contents into the thoracic cavity.
**Why Each Wrong Option is Incorrect**
**Option A:** Pneumothorax is a condition characterized by air in the pleural space, which may cause respiratory distress but does not explain the scaphoid abdomen or absent breath sounds on one side.
**Option B:** Diaphragmatic paralysis is a condition where the diaphragm is unable to contract, leading to respiratory distress, but it does not typically present with absent breath sounds on one side or a scaphoid abdomen.
**Option C:** Pneumonia is an infection of the lung parenchyma, which may cause respiratory distress, but it does not explain the scaphoid abdomen or absent breath sounds on one side.
**Clinical Pearl / High-Yield Fact**
A key clinical feature of CDH is the "scaphoid abdomen," which is a result of the displacement of abdominal contents into the thoracic cavity. This sign is often overlooked in the initial assessment, leading to delayed diagnosis.
**Correct Answer:** C. Congenital diaphragmatic hernia.