Question

A full-term newborn, delivered via elective C-section, develops tachypnea within 2 hours of birth. There is no significant retraction or grunting. Oxygen support is started. After 24 hours, the infant is well, off oxygen, and feeding normally. Which chest X-ray finding is most likely in this condition?

• A. Ground-glass opacities with air bronchograms
• B. Patchy infiltrates and hyperinflated lungs
• C. Prominent vascular markings and fluid in interlobar fissures
• D. Normal lung fields with elevated diaphragm

Hint:

Neonatal Chest X-Ray Patterns:
$\bullet$ TTN (Term + Elective C-Section): Fluid in fissures + Perihilar vascular streaking ("wet lung").
$\bullet$ RDS (Preterm): Ground-glass reticulogranular pattern + Air bronchograms.
$\bullet$ MAS (Post-term + Meconium): Coarse patchy infiltrates + Hyperinflation.

Answer 1

The Correct Option is C

Concept:
Transient Tachypnea of the Newborn (TTN), also known as "wet lung syndrome", is a benign, self-limiting respiratory disorder of term and late-preterm neonates caused by delayed clearance and reabsorption of fetal alveolar lung fluid.
Elective cesarean delivery without labor is the single strongest risk factor because the infant misses the labor-induced catecholamine surge that activates epithelial sodium channels (ENaC) to clear alveolar fluid.
Explanation:
• In normal vaginal delivery, labor triggers a surge in maternal and fetal catecholamines and steroids, which switches alveolar epithelial cells from active chloride secretion to active sodium and water absorption via ENaC channels, while thoracic squeezing clears remaining fluid.

• In elective cesarean deliveries without prior labor, this resorptive mechanism is blunted, leaving excess retained fluid within the alveolar spaces and pulmonary interstitial lymphatics.

• Neonates present within 1--2 hours of birth with tachypnea (respiratory rate $>60\text{ breaths/min}$), which typically improves rapidly and resolves completely within $24\text{ to }72\text{ hours}$ with minimal supportive care (low-flow oxygen).

• The characteristic chest radiographic findings in TTN include:
1. Fluid in the interlobar fissures (most notably the horizontal minor fissure)
2. Prominent perihilar vascular markings ("sunburst" perihilar streaking)
3. Mild symmetrical hyperinflation with flattening of the diaphragms
4. Cardiomegaly/prominent cardiac silhouette (transient)

• Ground-glass opacities with air bronchograms are classic for Respiratory Distress Syndrome (surfactant deficiency in preterms); patchy infiltrates with hyperinflation are typical of Meconium Aspiration Syndrome.
Final Answer:
The classic chest X-ray appearance of Transient Tachypnea of the Newborn consists of prominent perihilar vascular markings and fluid in the interlobar fissures.