## Meconium Aspiration Syndrome (MAS) — Radiological Hallmark **Key Point:** The classic chest X-ray appearance of MAS is a combination of **hyperinflation with patchy atelectasis interspersed with areas of hyperinflucency** — often described as a "ball-in-glove" or "streaky" pattern. ### Radiological Features of MAS | Finding | Description | Timing | |---------|-------------|--------| | **Hyperinflation** | Flattened diaphragms, increased AP diameter | Early (0–12 hrs) | | **Patchy atelectasis** | Irregular opacities, often perihilar | Early to mid-phase | | **Hyperinflucent areas** | Overdistended alveoli with air trapping | Persistent | | **Streaky infiltrates** | Linear opacities following bronchi | Characteristic | | **Pneumothorax/pneumomediastinum** | Air leak (10–40% of cases) | Variable | **High-Yield:** The **combination of hyperinflation + patchy infiltrates + areas of normal/hyperinflucent lung** is the radiological signature that distinguishes MAS from other neonatal respiratory conditions. ### Differential Diagnosis - **Respiratory Distress Syndrome (RDS):** Bilateral ground-glass opacities with air bronchograms ("reticulogranular" pattern); uniform involvement; seen in preterm infants. - **Neonatal Pneumonia:** Lobar or segmental consolidation; may have pleural effusion; more uniform pattern. - **Transient Tachypnea of Newborn (TTN):** Hyperinflation with fluid in interlobar fissures; resolves within 48–72 hours; bilateral symmetric. **Clinical Pearl:** MAS typically occurs in term or post-term infants with perinatal asphyxia history; RDS in preterm infants. The radiological pattern helps narrow the differential immediately. [cite:Caffey's Pediatric Diagnostic Imaging 13e Ch 38] 
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