Pediatric Chest Imaging

Normal Chest & Variants - Tiny Thorax Tour

• Thymus: Prominent in infants; variable appearance.
  • Sail sign: triangular opacity, often right upper lobe (RUL).
  • Wave sign: undulating border from rib indentations.
  • Notch sign: inferiorly at cardiophrenic angle.
• Cardiothoracic Ratio (CTR):
  • Neonate: < 0.6
  • Infant (<1yr): < 0.55
  • Child (>1yr): < 0.5
• Ribs: More horizontal. Adequate inspiration: 8-9 posterior ribs visible.
• Lungs: Appear more hyperlucent than adult lungs.
• Trachea: Slight rightward deviation is common.
• Common Variants: Azygos lobe/fissure.

⭐ The thymic sail sign and wave sign are classic normal findings in infants and young children, not to be mistaken for consolidation or mass.

Congenital Anomalies - Born This Way Lungs

• Congenital Diaphragmatic Hernia (CDH): Herniation of abdominal contents into thorax; pulmonary hypoplasia.
  • Bochdalek (posterolateral, L>R), Morgagni (anteromedial).
• Congenital Pulmonary Airway Malformation (CPAM): Hamartomatous lung lesion; communicates with airway. Types 0-4.
• Pulmonary Sequestration: Non-functioning lung; systemic arterial supply; no normal bronchial communication.
  • Intralobar (ILS): No own pleura; drains to pulmonary veins.
  • Extralobar (ELS): Own pleura; drains to systemic veins.
• Bronchogenic Cyst: Foregut duplication; mediastinal/intrapulmonary; no airway communication.
• Congenital Lobar Emphysema (CLE): Lobar overinflation; check-valve mechanism.

⭐ Bochdalek hernia: most common CDH (~85%), posterolateral, usually left; scaphoid abdomen.

Infections & Inflammations - Little Lung Invaders

Key differences in common pediatric pneumonias:

> ⭐ Round pneumonia is characteristic in children <**8** years due to underdeveloped pores of Kohn and canals of Lambert.

• Miliary TB: Diffuse, fine 1-2 mm nodular opacities (millet seed pattern) throughout both lungs.

Neonatal Distress - First Breath Battles

• Respiratory Distress Syndrome (RDS): Prematurity, surfactant deficiency.
  • CXR: Fine reticular/ground-glass opacities, air bronchograms, low lung volumes.
• Transient Tachypnea of Newborn (TTN): Delayed resorption of fetal lung fluid.
  • CXR: Perihilar streaking, fluid in fissures, pleural effusions. Resolves 24-72 hrs.
• Meconium Aspiration Syndrome (MAS): Post-term, fetal distress.
  • CXR: Coarse, patchy opacities, hyperinflation, risk of pneumothorax.
• Neonatal Pneumonia: Group B Strep common.
  • CXR: Diffuse alveolar opacities, consolidation; can mimic RDS.
• Pulmonary Interstitial Emphysema (PIE): Barotrauma (ventilated infants).
  • CXR: Linear or cystic lucencies.

⭐ Respiratory Distress Syndrome (RDS) classically presents with fine reticular or ground-glass opacities and prominent air bronchograms on chest X-ray, primarily due to surfactant deficiency in premature infants.

Airway Issues & Tumors - Windpipe Woes & Growths

• Croup (Laryngotracheobronchitis): Viral; subglottic edema. X-ray: Steeple sign (AP).

• Epiglottitis: Bacterial; supraglottic. X-ray: Thumb sign (lateral). ⚠️ Emergency.

• Foreign Body Aspiration (FBA): Peak 1-3 yrs. Expiratory X-ray: air trapping, mediastinal shift.

  ⭐ The right main bronchus is the most common location for inhaled foreign body aspiration in children.

• Tracheomalacia: Dynamic tracheal collapse (expiration). Fluoroscopy/CT.

• Pediatric Mediastinal Masses:

  Compartment	Common Masses
  Anterior	📌 "4 T's": Thymus, Teratoma, Thyroid, Terrible Lymphoma
  Middle	Lymphadenopathy (lymphoma, TB), Cysts (Bronchogenic, Duplication)
  Posterior	Neurogenic (Neuroblastoma - common), Cysts (Duplication)

High‑Yield Points - ⚡ Biggest Takeaways

• Thymic "sail sign" on CXR is normal in infants, not a mass.
• RDS shows diffuse ground-glass opacities, air bronchograms, and low lung volumes.
• TTN presents with perihilar streaking, interlobar fluid, resolving in 24-72 hrs.
• MAS features coarse, patchy infiltrates, hyperinflation, and risk of pneumothorax.
• CDH (Bochdalek) has bowel in chest, scaphoid abdomen, usually left-sided.
• Round pneumonia is common in children <8 years, appearing as a posterior round opacity.
• Foreign body aspiration causes unilateral air trapping (expiratory/decubitus views).