A 2-hour-old male neonate born at 32 weeks gestation to a primigravida mother (no antenatal steroids given) presents with grunting, nasal flaring, and intercostal retractions. Oxygen saturation is 88% on room air. Clinical suspicion for Respiratory Distress Syndrome (RDS) is high. Which investigation is most appropriate to confirm the diagnosis?

Explanation

## Diagnostic Approach to Neonatal RDS **Key Point:** Chest X-ray is the gold standard imaging investigation to confirm Respiratory Distress Syndrome in a symptomatic neonate. It provides definitive radiological evidence and helps exclude other causes of respiratory distress. ### Classic CXR Findings in RDS | Finding | Description | Timing | |---------|-------------|--------| | **Ground-glass appearance** | Diffuse, fine granular opacity | Early (1–6 hours) | | **Air bronchograms** | Bronchi silhouetted against opacified lung | Pathognomonic for RDS | | **Reticulogranular pattern** | "Salt-and-pepper" appearance | Progressive | | **Atelectasis** | Reduced lung volumes, elevated diaphragm | Severe cases | | **Hyperinflation** | Flattened diaphragm (late, if mechanical ventilation) | After intubation | **High-Yield:** The combination of **ground-glass opacity + air bronchograms** on CXR in a preterm neonate with clinical signs of respiratory distress is diagnostic of RDS. No other investigation is needed to confirm the diagnosis once clinical suspicion is high. **Clinical Pearl:** CXR should be obtained within the first 6 hours of life in any preterm infant with respiratory distress. Serial CXRs help track disease progression and response to surfactant therapy. ### Why CXR is Superior to Other Investigations ```mermaid flowchart TD A[Preterm neonate with respiratory distress]:::outcome --> B{Confirm RDS diagnosis?}:::decision B -->|Imaging needed| C[Chest X-ray]:::action C --> D[Ground-glass + air bronchograms]:::outcome D --> E[RDS confirmed]:::outcome B -->|Assess severity/complications| F[Blood gas analysis]:::action B -->|Antenatal risk assessment| G[L/S ratio from amniotic fluid]:::action G --> H[Antenatal decision-making only]:::outcome ``` **Key Point:** L/S ratio is an **antenatal** test (performed on amniotic fluid before delivery) to assess fetal lung maturity risk. It cannot be used to confirm RDS after birth. Blood gas analysis reflects the **severity** of RDS (hypoxemia, hypercapnia, acidosis) but does not confirm the diagnosis — it is a functional assessment, not a diagnostic test.