Lung volume and pattern separate the causes: low volume with granular opacity (surfactant deficiency), high volume with streaky perihilar opacity and fissural fluid (transient tachypnoea), patchy asymmetric opacity with hyperinflation (meconium aspiration) — and the lines, tubes and air leaks come first.
Orient first
- Gestational age and timing narrow the list: preterm (surfactant deficiency), term caesarean (transient tachypnoea), post-term with meconium (aspiration).
- Group B streptococcal pneumonia can mimic surfactant deficiency — effusions favour pneumonia.
- Congenital diaphragmatic hernia, pneumothorax and cardiac disease are the surgical and cardiac mimics.
Acquire the study
- Supine AP chest radiograph, including the upper abdomen for tube and line tips; horizontal-beam lateral or decubitus view for a suspected pneumothorax.
The manoeuvre
- Tubes and lines first: ETT tip between the clavicles and carina (at the first–second thoracic vertebrae), UVC tip at the IVC–right atrial junction, UAC tip at the sixth–ninth thoracic or third–fourth lumbar level (verify unit protocol).
- Lung volume: count posterior ribs above the diaphragm (≥ 9 = hyperinflated, ≤ 7 = low volume).
- Pattern: diffuse ground-glass with air bronchograms (surfactant deficiency) vs perihilar streaks and fissural fluid vs coarse asymmetric opacity.
- Air leak: pneumothorax (anterior lucency on a supine film), pneumomediastinum (spinnaker sail), interstitial emphysema.
- Heart size and pulmonary vascularity; bowel loops in the chest (CDH).
What confirms it
- A pattern consistent with a named cause in the right clinical and gestational context.
What licenses you to exclude it
- A clear chest radiograph in a distressed neonate prompts cardiac, metabolic and airway causes.
The classic misread
- Missing an anterior pneumothorax on a supine radiograph — look for a hyperlucent hemithorax and a sharp heart border.
- Reading thymus as consolidation.