Chest X-Ray Findings in Meconium Aspiration Syndrome
The correct answer is B: Patchy infiltrates with areas of hyperinflation and atelectasis is the characteristic chest X-ray finding in meconium aspiration syndrome. 1, 2
Radiographic Features of MAS
The chest X-ray in meconium aspiration syndrome demonstrates a distinctive pattern that reflects the underlying pathophysiology:
Patchy infiltrates (opacifications) combined with hyperinflation are the hallmark radiographic findings, resulting from the dual mechanisms of airway obstruction and chemical pneumonitis 1, 2
Areas of atelectasis occur due to complete airway obstruction by meconium plugs and surfactant inactivation 3, 1
Hyperinflation develops from ball-valve obstruction where meconium allows air entry but prevents complete exhalation, leading to gas trapping 4, 2
Why Other Options Are Incorrect
Option A (Ground-glass appearance with air bronchograms) is characteristic of respiratory distress syndrome (RDS), which occurs primarily in premature infants (<1,500 g birth weight), not the post-term infants typically affected by MAS 1
Option C (Diffuse bilateral opacities with air bronchograms) describes a more uniform pattern inconsistent with the patchy, irregular distribution seen in MAS 1
Option D (Normal lung fields) is incompatible with the diagnosis of MAS, as respiratory distress with meconium-stained fluid requires radiographic abnormalities to confirm the syndrome 2, 5
Clinical Context
MAS occurs in approximately 3-5% of neonates born through meconium-stained amniotic fluid, predominantly in post-term deliveries (≥42 weeks gestation) 1
The radiographic pattern correlates with ultrasound findings showing B-pattern (interstitial), consolidations, atelectasis, and bronchograms that vary with time as meconium redistributes in the lungs 6, 7
The heterogeneous appearance on imaging reflects the variable distribution of meconium plugs causing both complete obstruction (atelectasis) and partial obstruction (hyperinflation) in different lung regions 4, 2